Patent Publication Number: US-2005120414-A1

Title: Regulation of polynucleic acid activity and expression

Description:
This application is a continuation-in-part of U.S. application Ser. No. 10/644,288, filed Aug. 20, 2003, which is a continuation-in-part of U.S. application Ser. No. 10/354,903, filed Jan. 29, 2003, which claims priority to U.S. provisional application Ser. No. 60/352,705 filed Jan. 29, 2002, each of which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION  
      The invention relates to methods and systems for controlling the activity of preselected polynucleic acid molecules.  
     BACKGROUND OF THE INVENTION  
      U.S. Pat. No. 5,597,697, hereby incorporated by reference in its entirety, discloses polymerase-based methods for controlling the activity of preselected polynucleic molecules by rendering these molecules templates for the template-directed polymerization of nucleic acids.  
      RNA silencing is a cellular, sequence-specific RNA degradation mechanism that occurs in a broad range of eukaryotic organisms including fungi (quelling), animals (RNA-interference, RNAi) and plants (post-transcriptional gene silencing, PTGS). In these organisms, RNA silencing is triggered by double-stranded RNA (dsRNA) and requires a conserved set of gene products. Recent reviews of RNA silencing in plants include Matzke et al , Science 293, 1080-1083 (2001); Vance and Vaucheret, Science 292,, 2277-2280 (2001); Voinnet, Trends Genet., 17, 449-459 (2001) and Waterhouse et al., Nature, 411, 834-842 (2001), and in fungi or animals, Cogoni and Macino, Current Opin. Genet. Dev. 10, 638-643 (2000); Bernstein et al. Nature, 409, 363-366 (2001); Carthew, Curr. Opin. Cell Biol. 13, 244-248 (2001); Zamore, Natl. Sruct. Biol. 8, 746-750 (2001); and Nishikura, Cell 107, 415-418 (2001), each of which is hereby incorporated by reference in its entirety.  
      The mechanism of RNA silencing is proposed to involve processing of a “long” inducing dsRNA molecule into dsRNA fragments of 21 to 25 nucleotides. The enzyme Dicer, a member of the RNAse III family of dsRNA ribonucleases, digests an inducer dsRNA. Successive cleavage events degrade the 21-25 nucleotide fragments into 19-21 bp duplexes (small interfering RNAs, “siRNAs”) having 2-nucleotide 3′ overhangs. The siRNAs are proposed to then associate with the RNA-induced silencing complex (RISC) to target and degrade mRNA molecules having complementarity to the siRNA. In at least some systems, such as plants, the siRNA strands can serve as primers to render a target mRNA a template for template directed polymerization of ribonucleotides and further RNAse III-type dsRNA nuclease activity to inactivate the protein coding activity of the target molecule and generate further siRNAs. Since primer extension from a strand of siRNA proceeds in a 5′ to 3′ direction with respect to the primer strand, regions of the target RNA molecule upstream (in the 5′ direction with respect to the template) can become double stranded and themselves give rise to further RNA sequencing of the same or other RNA molecules in a cell that have homology or complementarity to these upstream regions.  
      Synthetic siRNAs are capable of inducing an RNA-silencing response in human and other mammalian cells that are not substantially capable of processing dsRNA to siRNA. Short RNA hairpins (stem-loop structures) can also be used to induce RNA silencing against RNA targets having regions of complementarity to at least one strand of the stem sequence of such the hairpin. (Discussed in Piccin et al, Nucleic Acids Res. Vol. 29, No. 12. e55, 2001, and Wesley et al., Plant J 27(6): 581-590, 2001, each incorporated by reference herein.) RNA:DNA hybrid molecules are also reported to be capable of triggering the RNA-silencing mechanism, as disclosed in published U.S. patent application Ser. No. 09/920,342.  
     SUMMARY OF THE INVENTION  
      A feature of certain embodiments of the invention is the incorporation of a functional polymerase binding site sequence (PBS) into a nucleic acid molecule that confers a discernible characteristic (for example via its sequence specific activity) such that the incorporation of the PBS renders the nucleic acid molecule a functional template for a given RNA or DNA template-directed nucleic acid polymerase. In the presence of the polymerase and any necessary primer molecules, catalytic extension of the strand of nucleic acids complementary to the template occurs, resulting in the modulation (decrease or increase) of the characteristic-conferring activity of the template molecule.  
      The invention provides methods and compositions for inhibiting the expression of, or other activities of, selected polynucleic acid molecules, for example, specific cellular and/or viral mRNA transcripts. The invention further provides methods and compositions for inhibiting the replicative ability of specific polynucleic acid molecules within a cell, for example viral genomes such as, but not limited to, plus or minus strand viral genomic RNA molecules.  
      The invention also provides RNA mediator molecules mediating RNA silencing against RNA molecules comprising a preselected sequence or its complement in response to RdRp activity in a cell, the RNA mediator molecule, that include a preselected polymerase binding site (PBS) utilizable by an RdRp of a virus and at least one preselected sequence element located upstream of the PBS (in the 5′ direction) in the RNA mediator molecule, the RNA mediator molecule thereby rendered capable of serving as a template for the RdRp in its presence so that the at least one sequence element becomes double stranded and an RNA silencing response against RNA molecules having homology with or being complementary to the at least one sequence element is triggered. The invention further provides cells and organisms containing such mediator molecules, for example, by transcribing such mediator molecules from transgenes, and methods for producing such cells and organisms.  
      The invention also provides methods and compositions that render a cell or multi-cellular organism resistant to viral infection. The invention further provides diagnostic methods and compositions for detecting the presence of a preselected virus in a sample.  
      The invention further provides methods and compositions for regulating the expression of a preselected gene in a cell, e.g. a transgene, by selectively rendering mRNA molecules encoding a transcriptional regulatory protein (or transcription-regulating RNA molecule) controlling the expression of the preselected gene to be a functional template for a template directed polynucleic acid polymerase or by otherwise selectively rendering such mRNA molecules targets of an RNA silencing mechanism in response to a preselected condition.  
      The invention provides a method for regulating the expression of a preselected gene in a cell, which comprises the steps of: providing at least one cell or multi-cellular organism wherein the expression of the preselected gene is under the control of a preselected transcriptional regulatory protein (or transcription-regulating RNA molecule) expressed from a gene in the cell; and causing the mRNA transcript for the transcriptional regulatory protein (or the transcription-regulating RNA itself to serve as a template for the template directed polymerization of nucleic acids to that the activity of the transcriptional regulatory protein (or transcription regulating RNA) in the cell is diminished. The transcriptional regulatory protein can be a transcriptional repressor protein or a transcriptional activator protein. At least one of the preselected gene and the gene encoding the transcriptional regulatory protein (or transcription regulating RNA) can be a transgene. The preselected gene can be of the sort that does or does not naturally occur under control of the transcriptional regulatory protein (or transcription regulating RNA), generally or with respect to specific cell types embodying the invention. Such cells can, for example, be animal cells or plants cells and the invention further provides multi-cellular organisms comprising such cells.  
      The invention also provides cells wherein the expression of a preselected gene is responsive to infection of the cell by at least one predetermined virus, which cells comprise: a preselected gene, the expression of the gene being under the control of a preselected transcriptional regulator selected from the group consisting of a transcriptional regulatory protein or a transcription-regulating RNA molecule; a gene expressing the preselected transcriptional regulator, and means for causing the mRNA encoding the transcriptional regulatory protein or the transcription-regulating RNA molecule to serve as a template for the template directed polymerization of nucleic acids in response to infection by the virus so that the activity of the transcriptional regulator in the cell is diminished.  
      The invention further provides a method for excising a preselected DNA sequence element from a cellular genome, which comprises the steps of: providing a cell comprising a series of DNA sequences that includes an excisable sequence element that is bounded on either side by specific excision sequences, a repressible promoter operably linked to a gene encoding a site specific recombinase capable of recognizing the specific excision sequences, and a gene operably encoding a repressor protein specific for the repressible promoter; and causing the mRNA encoding the repressor protein to serve as a template for the template directed polymerization of nucleic acids so that the protein coding activity of the mRNA in the cell is diminished.  
      The invention still further provides cells wherein a preselected DNA sequence element is excisable from the cellular genome in response to infection of the cell by at least one predetermined virus, which cells comprise: a series of DNA sequences that includes an excisable sequence element that is bounded on either side by specific excision sequences, a repressible promoter operably linked to a gene encoding a site specific recombinase capable of recognizing the specific excision sequences, and a gene operably encoding a repressor protein specific for the repressible promoter; and means for causing the mRNA encoding the repressor protein to serve as a template for the template directed polymerization of nucleic acids in response to infection by the virus acids so that the protein coding activity of the mRNA in the cell is diminished. In one variation of the invention, the excisable sequence element comprises at least one preselected expression cassette for at least one preselected gene.  
      The invention also provides a method for inducing the expression of a preselected gene from a cellular genome, which comprises the steps of: providing a cell comprising a series of DNA sequences that includes a promoter, such as a constitutively-active promoter, a transiently-active promoter or an inducible promoter, linked to a preselected gene, the promoter and preselected gene being separated by a blocking sequence that is in turn bounded on either side by specific excision sequences, a repressible promoter operably linked to a gene encoding a site specific recombinase capable of recognizing the specific excision sequences, and a gene operably encoding a repressor protein specific for the repressible promoter; and causing the mRNA encoding the repressor protein to serve as a template for the template directed polymerization of nucleic acids so that the protein coding activity of the mRNA in the cell is diminished  
      The invention further provides cells wherein the expression of a preselected gene from the cellular genome is inducible or becomes inducible in response to infection of the cell by at least one predetermined virus, comprising: a series of DNA sequences that includes a promoter, such as a constitutively-active promoter, a transiently-active promoter or an inducible promoter, linked to a preselected gene, the promoter and preselected gene being separated by a blocking sequence that is in turn bounded on either side by specific excision sequences, a repressible promoter operably linked to a gene encoding a site specific recombinase capable of recognizing the specific excision sequences, and a gene operably encoding a repressor protein specific for the repressible promoter; and means for causing the mRNA encoding the repressor protein to serve as a template for the template directed polymerization of nucleic acids in response to infection by the virus so that the protein coding activity of the mRNA in the cell is diminished. In one variation of the invention, the blocking sequence comprises at least one preselected expression cassette for at least one preselected gene.  
      The invention still further provides a method for regulating the expression of a preselected gene in a cell, which comprises the steps of the steps of: providing a cell wherein the expression of the preselected gene is under the control of a preselected transcriptional regulatory protein expressed from a gene in the cell; and causing RNA silencing against the mRNA transcript for the transcriptional regulatory protein so that the activity of the transcriptional regulatory protein in the cell is diminished. The transcriptional regulatory protein can be a transcriptional repressor protein or a transcriptional activator protein.  
      The invention also provides a method for regulating the expression of a preselected gene in a cell, which comprises the steps of: providing a cell wherein the expression of the preselected gene is under the control of a preselected transcription-regulating RNA expressed from a gene in the cell; and causing RNA silencing against the transcription regulating RNA.  
      The invention further provides cells wherein the expression of a preselected gene is responsive to the presence of polynucleic molecules having at least one region of known sequence, which cells comprise: a preselected gene, the expression of the gene being under the control of a preselected transcriptional regulator selected from the group consisting of a transcriptional regulatory protein or a transcription-regulating RNA molecule; a gene expressing the preselected transcriptional regulator; and means for rendering the mRNA of the transcriptional regulatory protein or the transcription-regulating RNA as a target for RNA silencing in response to the presence of the at least one polynucleic acid molecule comprising the predetermined sequence in the cell. The means can, for example, comprise preselected sequence of the transcriptional regulator gene or of an intermediate polynucleic molecule, that renders the RNA transcript of the transcriptional regulator gene as a target for RNA silencing as a result of the presence of the at least one polynucleic acid molecule comprising the known sequence in the cell.  
      The invention also provides cells wherein the expression of a preselected gene is responsive to the presence of polynucleic molecules having at least one region of predetermined sequence, which cells comprise: a preselected gene, the expression of the gene under the control of a preselected transcriptional regulator selected from the group consisting of a transcriptional regulatory protein or a transcription-regulating RNA molecule; and a gene expressing the preselected transcriptional regulator, wherein the gene expressing the preselected transcriptional regulator comprises sequence means rendering the RNA transcript of the gene as a target for RNA silencing as a result of the presence of the at least one polynucleic acid molecule comprising the predetermined sequence in the cell.  
      The invention still further provides a method for selectively excising a preselected DNA sequence from a cellular genome, which comprises the steps of: providing a cell comprising a series of DNA sequences that includes an excisable sequence element that is bounded on either side by specific excision sequences, a repressible promoter operably linked to a gene encoding a site specific recombinase capable of recognizing the specific excision sequences, and a gene operably encoding a repressor protein specific for the repressible promoter; and causing RNA silencing against the mRNA transcript for the repressor protein so that expression of the site specific recombinase is derepressed thereby causing excision of the excisable sequence element.  
      The invention also provides cells wherein a preselected DNA sequence is excisable from the cellular genome in response to the presence in the cell of a polynucleic acid molecule having at least one region of predetermined sequence, which cells comprise: a series of DNA sequences that includes an excisable sequence element that is bounded on either side by specific excision sequences, a repressible promoter operably linked to a gene encoding a site specific recombinase capable of recognizing the specific excision sequences, and a gene operably encoding a repressor protein specific for the repressible promoter; and means for causing RNA silencing against the mRNA transcript for the repressor protein in response to the presence in the cell of a polynucleic acid molecule having the region of predetermined sequence so that expression of the site specific recombinase is derepressed thereby causing excision of the excisable sequence element. In one variation of the invention the excisable sequence element comprises at least one expression cassette comprising at least one preselected gene.  
      The invention further provides a method for bringing the expression of a preselected gene in a cellular genome under the control of a preselected promoter, which comprises the steps of: providing a cell comprising a series of DNA sequences that includes a first promoter, for example a transiently-active promoter, a constitutively-active promoter or an inducible promoter, linked to a preselected gene, the promoter and preselected gene being separated by a blocking sequence that is in turn bounded on either side by specific excision sequences, a repressible promoter operably linked to a gene encoding a site specific recombinase capable of recognizing the specific excision sequences, and a gene operably encoding a repressor protein specific for the repressible promoter; and causing RNA silencing against the mRNA transcript for the repressor protein so that expression of the site specific recombinase is derepressed thereby causing excision of the blocking sequence thereby operably linking the first promoter and the preselected gene. In one variation, the blocking sequence comprises at least one expression cassette comprising at least one preselected gene.  
      A related embodiment of the invention more generally provides a method for bringing the expression of a preselected gene in a cellular genome under the control of any preselected, proximity-dependent, cis-acting transcription regulating DNA element (“cis-acting element”), such as a repressor DNA element or promoter DNA element, which comprises the steps of: providing a cell comprising a series of DNA sequences that includes a cis-acting element linked to a preselected gene, the cis-acting element and preselected gene being separated by a blocking sequence that is in turn bounded on either side by specific excision sequences, a repressible promoter operably linked to a gene encoding a site specific recombinase capable of recognizing the specific excision sequences, and a gene operably encoding a repressor protein specific for the repressible promoter; and causing RNA silencing against the mRNA transcript for the repressor protein so that expression of the site specific recombinase is derepressed thereby causing excision of the blocking sequence thereby operably linking the cis-acting element and the preselected gene. In a related variation, the blocking sequence comprises at least one expression cassette comprising at least one preselected gene.  
      The invention still further provides cells wherein the expression of a preselected gene can be brought under the control of a preselected promoter in response to the presence in the cell of a polynucleic acid molecule having at least one region of predetermined sequence, which comprise: a series of DNA sequences that includes a first promoter, for example a transiently-active promoter, a constitutively-active promoter or an inducible promoter, linked to a preselected gene, the promoter and preselected gene being separated by a blocking sequence that is in turn bounded on either side by specific excision sequences, a repressible promoter operably linked to a gene encoding a site specific recombinase capable of recognizing the specific excision sequences, and a gene operably encoding a repressor protein specific for the repressible promoter; and means for causing RNA silencing against the mRNA transcript for the repressor protein in response to the presence in the cell of a polynucleic acid molecule having the region of predetermined sequence so that expression of the site specific recombinase is derepressed thereby causing excision of the blocking sequence thereby operably linking the first promoter and the preselected gene. In one variation, the blocking sequence comprises at least one expression cassette comprising at least one preselected gene.  
      A related embodiment of the invention more generally provides cells wherein the expression of a preselected gene can be brought under the control of any preselected, proximity-dependent, cis-acting transcription regulating DNA element (“cis-acting element”), such as a repressor DNA element or promoter DNA element, in response to the presence in the cell of a polynucleic acid molecule having at least one region of predetermined sequence, which comprise: a series of DNA sequences that includes a cis-acting element linked to a preselected gene, the cis-acting element and preselected gene being separated by a blocking sequence that is in turn bounded on either side by specific excision sequences, a repressible promoter operably linked to a gene encoding a site specific recombinase capable of recognizing the specific excision sequences, and a gene operably encoding a repressor protein specific for the repressible promoter; and means for causing RNA silencing against the mRNA transcript for the repressor protein in response to the presence in the cell of a polynucleic acid molecule having the region of predetermined sequence so that expression of the site specific recombinase is derepressed thereby causing excision of the blocking sequence thereby operably linking the cis-acting element and the preselected gene. In a related variation, the blocking sequence comprises at least one expression cassette comprising at least one preselected gene. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows the sequences and proposed secondary structures for the terminal 3′ polymerase binding sites of TMV, TYMV and BMV. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The term “polymerase binding site” (abbreviated PBS) as used herein is defined as a sequence element in a nucleic acid molecule that renders the molecule a template for a specified nucleic acid polymerase by mediating interaction between the polymerase and the nucleic acid molecule. Accordingly, primer binding sequences, promoter sequences, and origins of replication, as known to those in the field, are examples of polymerase binding sites. As illustrated in Orr et al, The Journal of Biological Chemistry, 267, 4177-4182 (1992), with a number of polymerases, including HIV-RT, primer extension assays can be performed utilizing heterologous PBS sequences (those not normally used by a given polymerase) as long as there is sufficient complementarity between a region of the template molecule and the primer molecule used. An example is the “combined” template-primer molecule poly(rA)-oligo(dT).sub.12-18. Such a template sequence, which is complementary to the primer in question, also constitutes a polymerase binding site as defined herein.  
      A feature of certain embodiments of the invention is the incorporation of a functional polymerase binding site sequence (PBS) into a nucleic acid molecule which is chosen for its ability to confer a discernible characteristic (for example via its sequence specific activity) such that the incorporation of the PBS renders the nucleic acid molecule a functional template for utilization by one or more predetermined RNA or DNA template-directed nucleic acid polymerases. In the presence of the polymerase, any necessary primer molecules, and any necessary accessory molecules, catalytic extension of the strand of nucleic acids complementary to the template occurs, resulting in a partial or total elimination of (or increase in) the characteristic conferring activity of the reporter-template molecule described due to the effects of the complementary strand or other polymerase-mediated effects.  
      A reporter template polynucleic acid molecule according to the invention is a polynucleic molecule (DNA or RNA) that confers some discernable characteristic, in vitro and/or in vivo, for example a cell phenotype altering activity.  
      The direct incorporation of a PBS sequence or sequences into, for example, an RNA reporter strand may be achieved by the ligation of double stranded DNA restriction enzyme fragments containing the PBS sequence into appropriate restriction sites of a double stranded DNA molecule which is a template for the transcription of an RNA reporter strand by a DNA-dependent RNA polymerase. Alternatively the incorporation of the PBS sequence can be achieved through site-directed mutagenesis of such a DNA molecule, the total chemical synthesis of the novel RNA reporter molecule (by, for example, the phosphoramidite method using an Applied Biosystems Model 392 DNA/RNA Synthesizer), or by any other method known in the field.  
      Examples of the activity of the reporter-template RNA molecule include, but are not limited to, the following types. The RNA can be a messenger RNA (mRNA) coding for a protein that confers a discernible characteristic. In this case the preferable form of the assay is cell-based such that the reporter-template RNA is produced within a suitable host cell along with the components necessary for the extension of the nucleic acid strand complementary to the reporter-template molecule, specifically the appropriate RNA-dependent nucleic acid polymerase and its necessary primer molecule if any. The characteristic-conferring protein may be, but is not limited to, an enzyme catalyzing a color reaction such as beta-galactosidase (catalyzes the chromogenic conversion of the substrate 5-bromo-4-chloro-3-indolyl-beta-D-galactoside), an enzyme conferring antibiotic resistance, such as beta-lactamase, which confers resistance to ampicillin, or an enzyme conferring the metabolic complementation of an auxotrophic state. For cell-based and multi-cellular organism-based embodiments of the invention, the characteristic conferring activity can relate to any alteration of cellular phenotype.  
      Alternative positions for the incorporation of a PBS into an mRNA molecule with respect to the positions of the start codon and stop codon of the mRNA molecule include the following. The PBS can be incorporated into the 3′ non-coding sequence of the mRNA. The PBS can also be incorporated into the protein coding sequence of the mRNA. Incorporation of the PBS into the coding region is appropriate as long it does not change the coding sequence such that a non-functional characteristic-conferring protein is produced.  
      The PBS may also be incorporated within one or more introns within an mRNA transcript. Finally, the PBS can be incorporated into the 5′ non-coding region of the mRNA. This region contains the ribosome binding site and other regulatory sequences. Polymerase activity initiated by binding at the PBS in any of these regions can prevent translation of the mRNA by at least one of several mechanisms such as a direct block of sense strand translation by the complementary strand, the complementary strand-facilitated degradation and/or modification of the sense strand by enzymes such as RNAse H (specifically hydrolyzes the phosphodiester bonds of RNA in RNA:DNA duplexes to generate products with 3′ hydroxyl and 5′ phosphate ends.) and RNAse III (degrades RNA:RNA duplexes), e.g.,  E. coli  RNAse III, interference with the RBS by formation of its complementary strand and/or its degradation. Binding of the polymerase to its PBS without the ensuing synthesis of the complementary strand may also prevent translation due to steric interference with the translational apparatus, in particular this may be expected to occur if the PBS sequence is located near the RBS or between the RBS and the end of the protein coding sequence, but not in the 3′ non-coding region or necessarily at other sites 5′ to the RBS in the 5′ non-coding region. The choice of PBS incorporation sites will be influenced by the specific primer or PBS requirements, or lack thereof, for a particular type of template directed nucleic acid polymerase. The invention is not limited by the use of single or multiple PBS sequences incorporated into one or more of the alternate positions described in the same mRNA molecule.  
      Any suitable type of primer molecule can be used to specifically prime the desired polymerase activity, when a primer is required or desired. One method of targeting a reverse transcriptase such as HIV-RT or HIV-RT derived polymerase to a target preselected polynucleic acid molecule in a cell is to provide the cell with the expression of an HIV-RT primer such as human tRNA Lys-3  modified so that its 3′ polynucleotide sequence is complementary to a sequence of the target molecule. Such expression may be provided by introduction of a primer transgene into a cell, or multi-cellular organism, as part of an expression cassette, and/or by genetically modifying a preexisting cellular gene for tRNA Lys-3 , for example, by homologous recombination techniques. The polymerase binding site and primer requirements for HIV-RT are disclosed in Weiss et al, Gene, 111, 183-197 (1992) and Kohlstaedt and Steitz, Proc. Natl. Acad. Sci. USA 89, 9652-9656 (1992). Those for HBV-RT are disclosed in Wang and Seeger, Cell, 71, 663-670 (1992).  
      Many different RNA-dependent RNA polymerases (RdRp&#39;s) can be used according to the invention. These include, for example, RdRps of RNA viruses and cellular RdRp&#39;s of plants. Those skilled in the art will appreciate that any sort of cell can be genetically engineered to express a selected RdRp gene. Any suitable type of primer molecule can be used to specifically prime the desired RdRp activity according to which RdRp is selected. Many RNA virus genomes and satellite RNA virus genomes have a terminal 3′ integral primer or PBS that comprises secondary structure resembling tRNA. Examples of viruses with tRNA-like structure at the 3′ end of their genome include: Tymoviruses (e.g. turnip yellow mosaic virus, “TYMV”); Bromoviruses (e.g. brome mosaic virus, “BMV”); Cucumoviruses (e.g. cucumber mosaic virus), Hordeiviruses (e.g. barley stripe mosaic virus), Tobamoviruses (e.g. tobacco mosaic virus, “TMV”), Tobraviruses (e.g. tobacco rattle viruses).  FIG. 1A  shows a sequence and proposed secondary structure for the terminal 3′ polymerase binding sites of TMV.  FIG. 1B  shows the same for TYMV and  FIG. 1C  shows the same for BMV.  
      One method, according to the invention, of targeting an RdRp to a preselected RNA molecule in a cell is to provide the cell with the expression of a primer molecule based on the 3′ integral primer of the virus and modified so that its 3′ polynucleotide sequence is complementary to a sequence of the target molecule to be rendered a template. Another method, according to the invention, of targeting an RdRp to a preselected RNA molecule in a cell is to provide that the preselected RNA molecule includes a 3′ terminal PBS, for example, one that is characteristic of an RNA virus or other RdRp utilizing virus or determined to be utilized by a given RdRp , so that an RdRp is directed by the PBS to utilize the RNA molecule as a template for RNA polymerization. In one variation of this embodiment, the double-stranded RNA molecule formed by the RdRp using the preselected RNA molecule as a template is non-replicative. In a related variation, the inclusion of a PBS in the desired target RNA causes the target to serve as template for the template directed polymerization of ribonucleotides by the RdRp, but the target does not have and is not provided with PBS sequences or their complement that would cause the double stranded product of the polymerization to be exponentially amplified by nucleic acid polymerase activity in the cell(s) or vessel in which the elements of the invention are constituted and operative. In another variation of this embodiment, the inclusion of a PBS in the desired target RNA causes the target to serve as a template for the template directed polymerization of ribonucleotides by the RdRp, but the target does not have and is not provided with sequences that would cause the complementary RNA strand formed as a result of the template-directed polymerization to itself serve as a template for nucleic acid polymerase activity in the cell(s) or vessel in which the elements of the invention are constituted. Hence, in one example of this variation, the sequence of the part of the desired target RNA that serves as a template lacks a sequence complementary to a PBS functional in the cell(s), vessel or context in which the elements of the invention are constituted and operate, so that a functional PBS will not be formed in the RNA strand formed by RdRp activity using the target RNA as a template.  
      The invention is not limited by the means of incorporation of a PBS sequence into a polynucleic acid molecule to render it a template. In addition to altering the sequence of polynucleic acid molecule (or gene encoding it), these means also include the generation of a heterologous PBS by providing a primer sequence sufficiently complementary to a region of the polynucleic acid molecule without any modification of the template itself. The invention is not limited by the singularity, multiplicity, or position of PBS sequences incorporated into a reporter-template or other target polynucleic acid molecule nor is the invention limited by the nature of the discernible characteristic conferred by the reporter-template molecule or any target template molecule according to the invention.  
      For example, the reporter-template RNA molecule can be a regulatory RNA controlling the expression and/or other activity of one or more genes or gene products that confer a discernible characteristic. In this case also, the components comprising the invention may, for example, be produced within a suitable host cell.  
      In another example, the reporter-template RNA molecule can be a catalytic RNA molecule that confers a discernible characteristic directly, by virtue of its catalytic activity. This activity may include, but is not limited to the catalysis of color reactions. The catalytic reporter-template RNA molecule described can also be an RNA:DNA hybrid in which the incorporated primer and perhaps some other sequence of the molecule is composed wholly or partly of deoxyribonucleic acids.  
      The preceding discussion and examples also illustrate the manner in which any specific RNA molecule, whether naturally-occurring or genetically engineered, including but not limited to specific mRNA molecules and viral genomic RNA molecules, can be targeted according to the invention by one or more RNA-dependent nucleic acid polymerases, i.e., RNA-dependent RNA polymerases or reverse transcriptases, to inhibit or activate one or more activities of the targeted RNA molecule.  
      In reporter template embodiments related to DNA-dependent DNA polymerases, the reporter-template molecule can, for example, be a catalytic DNA molecule that confers a discernible characteristic directly, by virtue of its catalytic activity. This embodiment is analogous to that for RNA- dependent nucleic acid polymerases in which the reporter-template is a catalytic RNA. Functional interaction of a DNA-dependent DNA polymerase and the reporter-template reduces the catalytic activity of the reporter-template and provides an assay for inhibitors and activators of polymerase activity as previously described.  
      In reporter template embodiments related to DNA-dependent RNA polymerases the reporter-template may be a single stranded, partially double stranded, or double stranded DNA molecule that confers a discernible characteristic, for example, in a direct manner via its sequence specific catalytic activity. Such a reporter-template contains the promoter sequence and other sequences necessary to direct transcription of RNA. Functional interaction of a DNA-dependent RNA polymerase and the reporter-template reduces the latter&#39;s catalytic activity.  
      The cell-based embodiments of the invention may comprise any suitable host cell as long as the components of the invention are functional in the cell type in question. These host cell types may include, but are not limited to, mammalian cells, avian cells, fish cells, insect cells, plant cells, yeasts and bacteria.  
      RNA-degrading and/or modifying enzymes that may be used in accordance with the invention, as described, may for example be endogenous to the host cells or introduced by genetic methods to the host cells. In the case of in vitro, non-cell-based embodiments of the invention, enzymes such as nucleases can be directly provided to the composition or mixture comprising the invention.  
      Embodiments related to systems and methods for controlling the activity of polynucleic acid molecules within cells and multi-cellular organisms  
      In one embodiment, the invention provides a method for the controlling gene expression and, in general, the activity of any nucleic acid strand of interest. By operably linking the activity of a nucleic acid polymerase to a nucleic acid strand of interest, the expression of, or other activity of, the nucleic acid strand can be controlled by the addition and subtraction of the polymerase itself, cofactors of the polymerase such as but not limited to primer molecules if required for polymerase activity, or inhibitors and activators of the polymerase in question. In one embodiment of the invention, the cellular expression of a specified protein is controlled by operably linking the activity of an RNA-dependent nucleic acid polymerase to an mRNA molecule coding for the protein.  
      In another embodiment of the invention, the polynucleic acid molecule rendered subject to polymerase-mediated regulation is a viral replicative polynucleic acid molecule and the activity inhibited by the polymerase is the replicative activity of the polynucleic acid.  
      In still another embodiment of the invention, the polynucleic acid molecule rendered subject to polymerase-mediated regulation is a viral mRNA molecule or viral regulatory RNA molecule, and the activity inhibited by the polymerase is the viral function of the protein encoded by the viral mRNA molecule or the viral function of the viral regulatory molecule.  
      In a further embodiment of the invention, the polynucleic acid molecule rendered subject to polymerase-mediated regulation comprises a polynucleic acid aptamer (DNA or RNA) molecule having specific binding activity to one or more ligand molecules, as known in the art. Thus, the invention provides a method for reducing the binding between a polynucleic acid aptamer and a ligand to which the aptamer has characteristic binding affinity by rendering the aptamer a template for the template directed polymerization of nucleic acids by a template directed nucleic acid polymerase. Said polymerization can reduce the binding between the aptamer and its ligand by disrupting the characteristic ligand-binding secondary structure of the aptamer and/or by resulting in the degradation of the aptamer.  
      As disclosed above, in other embodiments of the invention the polynucleic acid molecule rendered subject to polymerase-mediated regulation is a regulatory polynucleic acid molecule or a catalytic polynucleic acid molecule.  
      According to the invention, a polymerase selected to inhibit the expression or other activity or function of a targeted polynucleic acid can be provided to the cell(s) in several ways. First, the polymerase may be a viral polymerase that is provided to the cell as a result of infection of the cell by a virus via, for example, (i) translation of polymerase-encoding mRNA which is part of an infecting virion, (ii) translation of polymerase-encoding mRNA which is transcribed from the viral genome within the cell and/or (iii) when the viral polymerase is a component of the virion itself (e.g., as can be the case for HIV) by direct delivery to the cell as a result of infection of the cell by the virus. Second, the cell may be genetically modified to express a suitable polynucleic acid polymerase, which polymerase is not otherwise expressed by the cell at all or at least not ordinarily expressed to a sufficient level to effectuate the desired polymerase-mediated inhibition. Third, the polymerase can be a polymerase endogenous to the cell(s) but which under normal cellular conditions is not substantially directed to a preselected polynucleic acid molecule for which inhibition is desired.  
      Inhibition of Multiple Target Molecules  
      Plant and animal cells can be engineered to express several different sequence specific primers targeting different transcripts and/or genomic elements for one or more specific viruses thereby imparting multiple viral resistances to the cell(s). Alternatively, or in addition, more than one cellular gene (endogenous or transgene) can be modified so that its transcripts comprise a PBS rendering the transcripts as templates for at least one nucleic acid polymerase.  
      Endogenous or Exogenous Polymerases  
      A polymerase selected for use according to the invention to modulate the activity of a target polynucleic acid molecule can, for example, be endogenous to the cell or multi-cellular organism, can be provided by a virus infecting the cell(s), or can be provided to the cell(s) or multi-cellular organism by genetically modifying the cell(s) or multi-cellular organism, according to standard methods, to express the polymerase. In some cases an identified cell type may be known to possess a desired, endogenous, template-directed nucleic acid polymerase activity although the enzyme responsible for the activity has not been identified. In this case, selecting a template directed nucleic acid polymerase for use according to the invention can comprise constituting the elements of the invention within cells of the cell type.  
      Selecting RNA or DNA Polymerases  
      For the suppression of mRNA transcripts or other RNA molecules, both RNA-directed DNA polymerases or RNA-directed RNA polymerases are suitable according to the invention. For the suppression of viral genomic replication in particular, the target suppressing polymerase selected may, for example, be of the type not utilized in normal viral replication. For example, the replication intermediates of RNA viruses that normally utilize a viral RNA-directed RNA polymerase for replication can be targeted by an RNA-directed DNA polymerase so that a replication-incompetent RNA:DNA hybrid is formed.  
      For example, in one embodiment of the invention, hoofed mammals susceptible to Foot and Mouth Virus (FMV) are genetically modified to make them resistance to infection by FMV. FMV is a single stranded, plus strand RNA virus. Normal replication of the FMV genome is dependent on an RNA-dependent RNA polymerase. There is no DNA replication intermediate in the FMV replication cycle. Thus, in one implementation of the invention, FMV susceptible animals are genetically modified to express a Reverse Transcriptase (RT) and primer molecule with a region of complementarity to the FMV plus strand which, together, target and inhibit replication of the plus strand RNA of FMV. In contrast to the double stranded RNA intermediate characteristic of FMV replication, FMV is not at all naturally equipped to replicate or serve as a template for transcription when the plus strand is complexed with complementary DNA to form an RNA:DNA hybrid, such as that formed by interaction with the RT.  
      RNAses or DNAses, integral to the polymerases, endogenous to the cell or engineered to be expressed in the cell, may also be employed according to the invention to degrade the target molecule as the selected polymerase utilizes the target as a template or at any point thereafter. Hence, in the FMV example above, if an RT having an integral RNAse H, such as HIV-RT, is used, the plus strand FMV RNA will be digested during reverse transcription. Examples of reverse transcriptase enzymes that lack RNAse activity and that can be used according to the invention include the various RNAse H domain/activity deficient mutants of HIV-RT that are known in the art. Members of the Dicer endonuclease family (Bernstein et al. Nature, 409, 363-366, 2001; Hutvagner et al. Science, 293, 834-838, 2001; Nicholson et al. Mamm Genome, 13(2), 67-73, 2002) of RNAse III type endonucleases are examples of nucleases suitable for digesting double stranded RNA molecules formed as a result of rendering an RNA molecule a template for an RNA-dependent RNA polymerase according to the invention.  
      Mispriming Techniques  
      One embodiment of the invention provides cells engineered with primers that redirect a viral polymerase to an “inappropriate starting point” along the viral genome, i.e., different than the primer binding site characteristically used by the virus, so that the formation of full length viral replication intermediates is at least partially inhibited. For example, engineered primers binding downstream (in the 3′ direction with respect to the primer) of the virus&#39; normal primer binding site cause a non-full length primer extension product to be formed rather than the virally-normal, replication-competent product. As a result, polymerase mediated synthesis of the full-length “virally-normal” product is at least partially inhibited. In one embodiment of this method, the viral polymerase contains an integral or closely associated nuclease, such as an RNAse H, that degrades the template during template-directed polymerization. In this manner, synthesis of the virally-normal, full-length product is precluded since some part of the template strand downstream of the PBS normally used by the virus is degraded, thereby preventing the formation of the characteristic full-length product from the characteristic PBS. An example of a polymerase with an RNAse H domain and which uses a characteristic viral PBS is HIV Reverse Transcriptase (HIV-RT).  
      Control of activity of preselected cell-encoded polynucleic acid molecules by redirection of viral polymerase activity to the cell-encoded molecules  
      According to one embodiment of the invention, cells may be engineered to express specific primer molecules that cause preselected cell-encoded polynucleic acid molecules (endogenous or transgenic) to serve as templates for viral polymerase activity, so that, upon infection of the cells with a virus providing the polymerase, the activity of the preselected polynucleic acid molecules coded by the genes (specific mRNAs molecules, regulatory RNA molecules, etc.) is modulated (reduced or increased) as a result of the functional interaction between the viral polymerase and the polynucleic acid molecule.  
      In another embodiment of the invention, a cellular gene (of endogenous origin or foreign origin with respect to the cell type) is genetically modified so that the single stranded polynucleic acid molecule product of the gene (ssRNA or ssDNA) comprises a functional polymerase binding site sequence (for example, as a result of altering the sequence of the gene or by providing for the cellular expression of a suitable primer) which renders the polynucleic acid molecule a template for the viral polymerase in the presence of the viral polymerase in the cell, thereby modulating the activity of the polynucleic acid molecule.  
      In a related embodiment, the target viral polynucleic acid molecule is an RNA molecule, the polymerase is an reverse transcriptase and the functional interaction between the polymerase and the target inhibits the viral function of the target.  
      In another related embodiment, the target viral polynucleic acid molecule is an RNA molecule, the polymerase is an RdRp and the functional interaction between the polymerase and the target, i.e., as a result of serving as a template, inhibits the viral function of the target. In a first variation, RNA silencing against RNA molecules in the cell or neighboring cells that have complementarity to a region of dsRNA formed by the polymerization is not caused as a result of the template-directed formation of dsRNA. In another variation, RNA silencing against RNA molecules in the cell or neighboring cells that have complementarity to a region of dsRNA formed by the polymerization is caused as a result of template-directed formation of dsRNA. In a subvariation, the cell is a plant cell.  
      Further embodiments of the invention provide methods and compositions of matter for controlling the activity of preselected RNA molecules in a cell or cells of an organism in response to viral RdRp activity within the cell or in other cells within the organism.  
      One embodiment of the invention provides a RNA mediator molecule including: a preselected PBS utilizable by an RdRp of a virus and at least one preselected sequence element located upstream of the PBS (in the 5′ direction) in the mediator molecule, the mediator molecule thereby rendered capable of serving as a template for the RdRp in its presence so that the at least one sequence element becomes double stranded and an RNA silencing response against RNA molecules having homology with or being complementary to the at lest one sequence element is triggered. Another embodiment provides for genetically modifying a cell to express such a mediator molecule or otherwise causing such a mediator molecule to be produced in a cell. Another related embodiment provides a plant cell comprising such mediator molecule or a plant comprising at least one Such plant cell. A different related embodiment provides an animal or human cell comprising such a mediator molecule. Still another embodiment of the invention provides a genome or vector capable of transcribing such a mediator molecule, a dsDNA cellular genome or a dsDNA plasmid vector encoding such a mediator molecule. The PBS of the mediator molecule can be of any sort, for example, a terminal 3′ tRNA-like viral PBS of an RNA virus. In one variation of these embodiments the part of the mediator molecule that serves as a template for the RdRp lacks sequence directing the formation of a functional PBS for an RdRp in the complementary strand. In another variation of these embodiments, the part of the mediator molecule that serves as a template for the RdRp lacks sequence directing the formation of a functional PBS for a viral RdRp in the complementary strand. In another variation of these embodiments, the part of the mediator molecule that serves as a template for the RdRp lacks sequence directing the formation of functional PBS for the same RdRp in the complementary strand, so that the complementary strand itself will not serve as a template for this RdRp. In a related variation, the at least partially double stranded RNA molecule resulting from the PBS directed use of the RNA mediator molecule as a template by the RdRp is non-replicative in a cell in which the elements of the invention are constituted and operable.  
      In a further variation of the aforementioned embodiments and its variations, the invention provides that at least one of the preselected sequence elements upstream of the PBS is selected to silence an RNA molecule of interest in a cell or cells. Hence, according to the invention, the sequence element may be selected to have homology with or complementary to the RNA molecule of interest, so that dsRNA formed by the RdRp will trigger silencing against the RNA molecule of interest. Such an RNA molecule of interest may, for example, be a cellularly transcribed RNA (of cellular origin or transgenic), such as regulatory RNA or an mRNA, or be a viral RNA molecule, such a viral genomic RNA, regulatory RNA or mRNA.  
      In one variation of the aforementioned embodiments and its variations, the preselected sequence element is homologous to a region of an RNA molecule of interest that will be silenced in response to the formation of dsRNA as a result of the RNA mediator molecule serving as a template for the RdRp. In a subvariation, the RNA molecule of interest is an mRNA molecule and the preselected sequence element is homologous to a region mRNA molecule. In another variation of the aforementioned embodiments and its variations, the preselected sequence element is complementary to a region of an RNA molecule of interest that will be silenced in response to the formation of dsRNA as a result of the RNA mediator molecule serving as a template for the RdRp. In a subvariation, the RNA molecule of interest is an mRNA molecule and the preselected sequence element is complementary to a region of the mRNA molecule.  
      In a still further variation of the aforementioned embodiment and its variations, the RNA mediator molecule is a functional mRNA (either as transcribed or in a mature processed state) comprising a coding sequence for a protein, for example a protein conferring a discernable characteristic and optionally including intronic sequences, so that the protein is expressed when an RdRp is not active in using the RNA mediator molecule as a template. In a subvariation, the preselected sequence element is comprised within the protein coding sequence or within an intronic sequence. In a different variation of the aforementioned embodiments and its variations, the RNA mediator molecule is not capable of acting a functional mRNA molecule, whether or not in a nascent state or in a mature processed state. For example, it may lack the features of an mRNA required for translation in a particular cell type, such as a start codon or a ribosome binding site.  
      In a still further variation of the embodiment and its variations, the complementary RNA molecule formed as a result of the use of the RNA mediator molecule as a template by the RdRp lacks functional mRNA activity, i.e., it cannot be translated into a protein by a cell in which the components of the invention are constituted and operative.  
      Those skilled in the art will appreciate that in certain organisms, such as plants, an RNA silencing response triggered in one cell can be transmitted to other cells in the organism, and that such effects are within the scope of the present invention.  
      Cellular resistance to virus via redirection of viral polymerase activity to viral polynucleic acids or polynucleic acids produced using the viral genome as a template  
      According to one embodiment of the invention, cells may be engineered to express specific primer molecules so that, in infected cells, preselected viral RNA molecules are targeted and their normal activity inhibited by at least one viral polymerase provided by the virus itself. In this context “provided” by the virus means that the polymerase polypeptide is already present in the virion when it enters the cell or that the virion contains mRNA coding for the polymerase, which mRNA is translated once in the cell or that the viral genome is capable of serving as a template for the transcription of mRNA coding for the polymerase, which mRNA is normally transcribed and translated in the cell. In this embodiment of the invention, the viral polymerase is directed to viral polynucleic acids or regions thereof, which do not normally serve as templates for the viral polymerase. In this manner, the normal activity of the viral nucleic acids is inhibited. For example, in the case of a virus providing a reverse transcriptase or an RNA-dependent RNA polymerase, a cell or multi-cellular organism can be genetically modified to express primer molecules that direct the polymerase to use an mRNA transcript of the virus as a template for the template directed polymerization of nucleic acids. In this manner, translation of the viral mRNA transcript can be inhibited.  
      A number of embodiments of the invention involving the targeting of polymerase activity to selected polynucleic acid molecules, such as RNA molecules, relate to the capacity for double-strand-mediated RNA silencing of the cells in which elements of the invention are constituted.  
      In one embodiment of the invention, the cells constituting the elements of the invention are not capable of RNA silencing in response to long dsRNA or long RNA/cDNA hybrid molecules and the rendering of a preselected RNA molecule to be template for a preselected polynucleic acid polymerase to modulate the activity of the polynucleic acid molecule forms a long dsRNA molecule or long RNA/cDNA hybrid which does not trigger RNA silencing of polynucleic acid molecules in the cell.  
      In a related embodiment, the cells constituting the elements of the invention are not capable of RNA silencing in response to long dsRNA or long RNA/cDNA hybrid molecules but are capable of RNA silencing in response to siRNAs or similar small RNA/cDNA hybrid molecules. Various mammalian cells including human cells have this characteristic. In a related variation, such cells are made to express a member of the RNAse III family, such as Dicer, to cause the long dsRNA or long RNA/cDNA hybrid molecules formed by rendering the preselected RNA molecule to be a template for a preselected polynucleic acid polymerase to reduce the activity of the polynucleic acid molecule to be processed into siRNAs or small RNA/cDNA hybrids which trigger RNA silencing of polynucleic acid molecules in the cell.  
      In a embodiment variation of the invention, the cells constituting the elements of the invention are incapable of RNA silencing in response to long dsRNA or long RNA/cDNA hybrid molecules, whether or not such molecules are processed by an RNAse III enzyme, and the rendering of a preselected RNA molecule to be a template for a preselected polynucleic acid polymerase to reduce the activity of the preselected polynucleic acid molecule forms such a long dsRNA molecule or long RNA/cDNA hybrid. In one embodiment of this variation, an RNAse III enzyme is expressed in the cell(s), for example, by genetically-modifying the cell(s) to express the enzyme, and the RNAse III processes the long dsRNA molecule or long RNA/cDNA hybrid but RNA silencing is not triggered in response. In accordance with the described role of RISC in RNA silencing, such a cell can be created by genetically modifying an otherwise RNAi-RNA silencing-competent cell to knock out, for example by homologous recombination, one or more components of the RISC complex.  
      In another embodiment, the cells constituting the elements of the invention are capable of RNA silencing in response to long dsRNA or long RNA/cDNA hybrid molecules and the rendering of a preselected RNA molecule to be a template for a preselected polynucleic acid polymerase, to modulate the activity of the preselected polynucleic acid molecule, forms such a long dsRNA molecule or long RNA/cDNA hybrid which further triggers RNA silencing of polynucleic acid molecules in the cell.  
      According to one embodiment of the invention, RNA silencing is triggered by rendering a preselected polynucleic acid molecule(s) a template in the cells embodying the invention, and the polynucleic acid molecules silenced may be other copies of the same preselected polynucleic acid molecule which may be present in the cell, similar polynucleic acid molecules encoded by the same gene or different polynucleic acid molecules encoded by different genes (endogenous or transgenic) which have regions of complementarity with at least one strand of a dsRNA or RNA:DNA hybrid molecule generated from the template, for example, with siRNA fragment(s) generated from a dsRNA generated from the template by polymerization.  
      In a related embodiment, the cells constituting the elements of the invention are capable of RNA silencing in response to long dsRNA but not in response to long RNA/cDNA hybrid molecules. In this variation, use of a reverse transcriptase to render a preselected RNA molecule to be template for a preselected polynucleic acid polymerase to reduce the activity of the preselected polynucleic acid molecule creates a long RNA/cDNA hybrid which does not trigger said RNA silencing, while use of a RNA-dependent RNA polymerase creates a long dsRNA which does trigger said RNA silencing against polynucleic molecules having complementarity to one of the strands of the dsRNA formed by action of the polymerase on the template.  
      In another embodiment of the invention, the cells constituting the elements of the invention are capable of RNA silencing in response to long RNA/cDNA hybrids but a reverse transcriptase having an integral or closely-associated RNAse H is used as the polymerase which renders the preselected polynucleic acid molecule as a template for template directed polymerization to degrade the template RNA and/or reduce the activity of the preselected polynucleic acid molecule. In this embodiment, a long RNA/cDNA hybrid is not formed as a result of the polymerization. In a similar related variation, the RNAse H is not integral or closely associated with the reverse transcriptase, but is nevertheless expressed in the cell and active against the RNA template component of the RNA/cDNA hybrid being formed by the reverse transcripts. In either case, the RNAse H may hydrolyze the RNA template strand as the cDNA is synthesized so that formation of a long RNA/cDNA hybrid molecule competent for RNA silencing is at least substantially not formed and RNA silencing is at least substantially prevented.  
      Transcriptional Regulatory Protein Embodiments of the Invention  
      A number of embodiments of the invention relate to the targeting of polymerase activity to selected mRNAs encoding transcription regulatory proteins or to transcription regulating RNA molecules, in order to affect the expression of genes of interest under the control of such regulatory molecules.  
      In this embodiment of the invention, the RNA molecule made to be a template for a viral polymerase is an mRNA coding for a transcriptional activator protein or a transcriptional repressor protein that activates or represses, respectively, the expression of one or more other preselected genes of any sort including, but not limited to: reporter genes, lethal/toxic genes, essential genes, cell phenotype altering genes, herbicide resistance genes, and genes which themselves code for a transcriptional regulatory protein controlling the expression of still one or more other genes. Further, the invention provides that the preselected genes can be of the sort found in nature under the control of the regulatory protein or can be genes not found in nature under control of the particular regulatory protein.  
      Several Embodiments of the Invention Relate to the Polymerase-targeting Mediated Derepression of Expression of Genes of Interest.  
      In one embodiment of the invention, an RNA molecule made to be a template for a viral polymerase is an mRNA coding for a transcriptional repressor protein which represses the expression, or is engineered to repress the expression of, one or more other preselected genes such as, but not limited to, a reporter gene or a suicide gene which causes an infected cell to die, thus limiting spread of the viral infection within a multi-cellular organism or to other organisms.  
      For example, a cell can be genetically modified so that the expression of the luciferase gene is repressed by a repressor protein that is expressed within the cell. The repressor protein used may be endogenous to the cell or expressed within the cell as a result of genetically modifying the cell. In any case, in this embodiment, the repressor protein transcript is operably-linked to the activity of one or more selected viral polymerases in the fashion of the invention. Upon infection of the cell(s), direction of the viral polymerase to this repressor gene transcript prevents its expression, thereby leading to derepression of, in this example, the luciferase gene. Addition of the luciferase substrate and action thereon by the luciferase enzyme, if its expression has been derepressed, will cause light to be emitted thus indicating the derepression. Another example of a reporter gene that can be used is green fluorescent protein (GFP) or any of its numerous derivatives known in the art. In this manner, a test system for the presence or absence of particular viruses can be provided.  
      The repressor protein coded by the repressor mRNA transcript may be an inhibitory transcription factor capable of directly interacting with the regulatory sequences of the repressed gene, whether endogenous or engineered, as known in the art or may indirectly interact with other biomolecules present in the cell to repress the repressed gene. For example, for plant embodiments of the invention, Tn10 tet repressor systems, as described in Gatz and Quail (1988) and Gatz, et al. (1992), can be adapted for use according to the invention. In this system, a modified Cauliflower Mosaic Virus (CaMV) 35S promoter containing one or more, e.g. three, tet operons is used; the Tn10 tet repressor gene produces a repressor protein that binds to the tet operon(s) and prevents the expression of the gene to which the promoter is linked. The presence of tetracycline inhibits binding of the Tn10 tet repressor to the tet operon(s), allowing free expression of the linked gene. Gatz and Quail, “Tn10-encoded tet repressor can regulate an operator-containing plant promoter,” Proc. Natl. Acad. Sci. USA, 85:1394-1397 (1988) and Gatz, et al., “Stringent repression and homogenous derepression by tetracycline of a modified CaMV 35S promoter in intact transgenic tobacco plants,” The Plant Journal, 2:397-404 (1992), hereby incorporated by reference in their entireties. However, the present invention is not concerned with regulation of the system by tetracycline, although such regulation for which the prior system was designed may optionally be left intact according to the present invention. Instead, according to the invention, the transcript for the repressor protein is made to serve as a template for the viral polymerase, thereby reducing the production of the repressor protein and activating expression driven by the modified CaMV 35S promoter.  
      Tetracycline responsive promoter systems known in the art for mammalian cells can similarly be adapted for use according to the invention. For example, U.S. Pat. Nos. 5,723,765 and 6,242,667 disclose suitable repressor systems, and are hereby incorporated by reference in their entireties. Those skilled in the art will appreciate that there are many characterized natural repressor and genetically engineered transcriptional activator protein and transcriptional repressor protein systems for plant and animal cells that can be routinely adapted to function according to the invention as described herein. Those skilled in the art will further understand that any gene of interest may be placed under the control of any operable transcriptional repressor or activator by genetically modifying a cell (stably or transiently) and that the repression or activation can be selectively modulated, according to the invention, by rendering the mRNA transcripts coding for the transcriptional regulator protein as functional templates for a template directed polynucleic acid polymerase.  
      One related embodiment provides introducing a series of sequences into a cell or multi-cellular organism that includes an excisable sequence element that is in turn bounded on either side by specific excision sequences, a repressible promoter operably linked to a gene encoding a site specific recombinase capable of recognizing the specific excision sequences, and a gene operably encoding a repressor specific for the repressible promoter. According to the invention, rendering the transcripts encoding the repressor protein as a template for template directed polymerization of nucleic acids, e.g. in response to some condition, reduces the expression of the repressor protein, thereby derepressing expression of the recombinase, thereby causing excision of the excisable sequence, thus altering the sequence of the DNA molecule in which the excisable sequence was previously found. In this manner, polymerase mediated inhibition of the protein coding activity of a preselected mRNA can be used to induce a genotypic change in a cell. The presence or absence of the genotypic change in the cell or within a population of such cells can be detected by standard methods, for example, PCR amplification. The resulting genotypic changes present in the cell and its progeny, if any, serve as a record of exposure to the condition that caused the genotypic change to occur, for example, infection of the cell by a particular virus. Thus, a variation of this embodiment of the invention provides another sort of diagnostic assay for viral infection.  
      Another related embodiment provides introducing a series of sequences into a cell or multi-cellular organism that includes a promoter, such as a constitutively-active promoter, a transiently-active promoter or an inducible promoter, linked to a preselected gene, the promoter and preselected gene being separated by a blocking sequence that is in turn bounded on either side by specific excision sequences, a repressible promoter operably linked to a gene encoding a site specific recombinase capable of recognizing the specific excision sequences, and a gene operably encoding a repressor specific for the repressible promoter. According to the invention, rendering the transcripts encoding the repressor protein as a template for template directed polymerization of nucleic acids, in response to some condition, e.g., provision of a viral polymerase by an infecting virus, reduces the expression of the repressor protein, thereby derepressing expression of the recombinase, thereby causing excision of the blocking sequence, thus providing for expression of the preselected gene. In this manner, polymerase mediated inhibition of the protein coding activity of an mRNA can be used to induce the expression of a preselected gene. In one such embodiment of the invention, the organism is a plant, the repressor protein is inhibited in response to provision of a viral polymerase and the preselected gene is, for example, a lethal/toxin gene or a reporter gene.  
      The CRE-LOX recombinase excision system, as disclosed for example in U.S. Pat. No. 5,723,765, has been employed for the purpose of selective recombination in numerous systems including plants and animals including mammals and their cells and is readily employed according to the present invention. Other enzymatic excision systems that can be employed according to the present invention include, for example, the resolvases, flippase, FLP, SSV1 encoded integrase, and the maize Ac/Ds transposase system (each also being disclosed in U.S. Pat. No. 5,723,765).  
      A gene and a cis-acting, transcription-regulating DNA element (“cis-acting element”), such as a repressor DNA element or promoter DNA element, are considered to be linked if they occur in the same strand of DNA or within the same double stranded DNA molecule. A gene and a cis-acting element are considered to be operably linked if they are linked and they occur in such relative orientation and proximity that the cis-acting element at least partially affects the transcription of the gene. The presence of intervening DNA between the cis-acting element and the gene does not preclude an operable relationship.  
      A blocking sequence is a DNA sequence of any length that at least substantially blocks a cis-acting element from affecting the transcription of a gene of interest.  
      As further discussed herein, when the condition triggering the polymerase-mediated inactivation of the repressor is the expression of a preselected RNA transcript (or any RNA transcript having a preselected sequence or sequence region) in the cells of a multi-cellular organism, for example according to normal developmental regulation, the recombinase derepression embodiment of the invention can be used to detect expression of the preselected RNA transcript generally and to trace the cellular lineage of expression of the preselected RNA transcript, both visibly, in real time, for example by using GFP or a derivative as a recombinase-derepressible gene, or by hybridization probing and/or histologically staining. In a further related embodiment, the derepression is performed on preselected cells in a developing embryo or tissue, for example by microinjection of a primer molecule into the cell(s) or other molecule capable of triggering the polymerase mediated inhibition of the repressor mRNA, in order to track and trace the behavior and/or lineage of the cells and their progeny. The promoter sequence that drives the expression of the preselected gene can, for example, be a constitutive promoter, a developmentally-regulated promoter, a tissue-specific promoter or an inducible promoter.  
      The repressor may also be a regulatory polynucleic acid that directly inhibits the activity, of a second polynucleic acid. For example, the repressor may be a catalytic polynucleic acid, such as a ribozyme or DNAzyme, engineered to cleave or otherwise degrade an mRNA transcript that encodes a peptide having, e.g., reporter activity or gene regulatory activity or cell phenotype altering activity of any sort. Here again, the cell is genetically modified so that the polynucleic acid repressor is operably linked to the activity of a viral nucleic acid polymerase, the functional interaction between the polynucleic acid molecule and the polymerase being regulated by entry of the virus into the cell.  
      When used to de-repress reporter genes, derepression embodiments of the invention can also be used to provide viral infection detection systems in plants and animals. When used to de-repress suicide genes, e.g., lethal/toxin genes, these derepression embodiments of the invention can also be used to provide viral infection-limiting cell death in plants and animals as described above. For example, in plant embodiments of the invention lethal nucleases such as Barnase and ribonuclease A and 2 can be used and catalytic lethal proteins such as diptheria toxin and ribosomal inhibitor proteins (RIP) can be used. Use of a ribosomal inhibitor protein (“RIP”) gene as a lethal gene for plants, e.g., the saponin 6 RIP, (GenBank H) SOSAPG, Accession No. X15655), is advantageous since RIP directly interferes in the expression of all protein in a plant cell, without being toxic to other organisms which ingest a plant having such cells.  
      Lethal/toxin genes applicable for animal cell embodiments of the invention include, but are not limited to: (a) apoptosis inducing tumor suppressor genes (e.g., p53), (b) cytotoxic genes (e.g., tumor necrosis factor, interferon-alpha), (c) suicide genes (e.g., cytosine deaminase, thymidine kinase), and (d) toxins such as pseudomonas endotoxin, ricin or diphtheria toxin subunits.  
      As a further example, genes coding for enzymes that convert a protoxin to a toxin can be used as the genes that are de-repressible according to the derepression embodiment. In this manner, cell death is made conditional on both the derepression of the converting enzyme and application of the protoxin to the cells/organism.  
      The invention is not limited to the type of cell or multi-cellular organism in which the invention is embodied or implemented. Further, cells and organisms in which the invention is embodied or implemented are within the scope of the invention. The genetic modification of cells and organisms, including complex organisms, to embody the invention, can be performed using any of the standard methods known in the art.  
      One embodiment of the invention comprises genetically modifying a cell or multi-cellular organism cell to render it capable of utilizing at least one preselected cell-encoded or viral polynucleic acid as a template for the template-directed polymerization of polynucleic acids by a template-directed polynucleic acid polymerase so that the activity of the polynucleic acid molecule is inhibited, wherein the cell or multi-cellular organism not so modified is at least substantially incapable of inhibiting the activity of the polynucleic molecule by utilizing it as a template for template-directed nucleic acid polymerization by a polynucleic acid polymerase. In one example of this embodiment, resistance to viral infection can be imparted to the cell or multi-cellular organism when the target polynucleic acid molecule is a viral genomic polynucleic molecule, viral replication intermediate polynucleic acid molecule, viral mRNA transcript, or other viral polynucleic acid molecule, the activity of which is required for, or contributes to, viral pathogenicity.  
      A further embodiment of the invention is directed to the above embodiment wherein the cell or multi-cellular organism not so genetically modified is at least substantially incapable of inhibiting the activity of the polynucleic molecule by utilizing it as a template for template-directed nucleic acid polymerization by a polynucleic acid polymerase, even upon providing the cell or multi-cellular organism, by genetic modification or otherwise, with putative primer molecules having a 3′ region of complementarity to the polynucleic acid molecule.  
      A still further related embodiment of the invention comprises, genetically modifying a cell or multi-cellular organism to express a template-directed polynucleic acid polymerase capable of utilizing the polynucleic acid as a template so that its activity is inhibited.  
      Another related embodiment further comprises genetically modifying the cell or multi-cellular organism to produce a polynucleic acid primer molecule capable of directing a template directed polynucleic acid polymerase not endogenous, i.e., not normally coded for or expressed by the cell, to utilize the polynucleic acid as a template so that its activity is inhibited. Such a polymerase includes, for example, one for which the cell is genetically engineered to express or that is provided by a virus as a result of infection of the cell by the virus.  
      A still further related embodiment of the invention comprises genetically modifying a cell or multi-cellular organism to express a preselected nuclease capable of degrading a target polynucleic acid molecule which has been rendered a template for a polymerase, during or after template directed nucleic acid polymerization by the polymerase, wherein the cell or multi-cellular organism otherwise lacks such a nuclease or wherein the efficiency of the degradation is increased by genetically modifying the cell or multi-cellular organism to express the preselected nuclease.  
      Another embodiment of the invention comprises providing the cell or multi-cellular organism with a template-directed polynucleic acid polymerase having an integral nuclease capable of degrading a preselected polynucleic acid molecule that serves as a template for the polymerase, during or after template directed nucleic acid polymerization by the polymerase, so that the activity of the preselected polynucleic acid molecule is inhibited.  
      The aforementioned polymerase-mediated, transcriptional regulatory molecule embodiments of the invention may, according to the invention, operate with or without the triggering of RISC-mediated RNA silencing against the regulatory protein mRNA molecules or transcriptional-regulating RNA molecules. Further embodiments of the invention provide methods, cells and compositions of matter for regulating gene expression in which RISC-meiated RNA silencing of transcriptional regulatory molecules controlling the expression of genes of interest is triggered by at least one mechanism.  
      According to the invention, any gene of interest may be placed under the direct or indirect control of any operable transcriptional repressor or activator by genetically modifying a cell (stably or transiently) and the repression or activation of the expression of the gene of interest can be selectively modulated, according to the invention, by (i) rendering the mRNA transcripts coding for the transcriptional regulator protein, or by (ii) rendering an RNA molecule which is itself the transcriptional regulator (for example, a ribozyme engineered to cleave the transcript of the gene of interest), as targets of an RNA silencing mechanism in response to a prespecified condition, i.e., a particular stimulus or triggering event. The RNA silencing embodiments of the invention that affect gene expression and/or alter genotype in a detectable manner in response to the presence in the cell of particular polynucleic acid sequences, for example, those that occur in a cell as a result of viral infection of the cells by particular viruses, also generally provide assays and test cells and organisms for the detection of such sequences, and their vectors if any, in a test sample, in the environment and/or in an organism comprising such test cells. Such assays can be conducted, for example, by contacting test cells with samples, optionally also using positive and/or negative controls, and by determining the extent to which the sample triggers the condition-specific, RNA silencing-mediated gene expression and/or genotypic changes, with or without comparison to any controls.  
      In one RNA silencing embodiment of the invention, an RNA molecule is rendered a target of RNA silencing in response to a prespecified condition and is an mRNA coding for a transcriptional activator protein or a transcriptional repressor protein that activates or represses, respectively, the expression of one or more other preselected genes of any sort including, but not limited to: reporter genes, lethal/toxic genes, essential genes, cell phenotype altering genes, herbicide resistance genes, and genes which themselves code for a transcriptional regulatory protein controlling the expression of still one or more other genes. Further, the invention provides that the preselected genes can be of the sort found in nature under the control of the regulatory protein or can be genes not found in nature under control of the particular regulatory protein.  
      In a related RNA silencing embodiment of the invention, an RNA molecule is rendered a target of RNA silencing in response to a prespecified condition and is an mRNA coding for a transcriptional repressor protein which represses the expression, or is engineered to repress the expression of, one or more other preselected genes such as, but not limited to, a reporter gene or a suicide gene which causes an infected cell to die, thus limiting spread of the viral infection within a multi-cellular organism or to other organisms.  
      Another RNA silencing related embodiment of the invention provides introducing a series of sequences into a cell or multi-cellular organism that includes an excisable sequence element that is in turn bounded on either side by specific excision sequences, a repressible promoter operably linked to a gene encoding a site specific recombinase capable of recognizing the specific excision sequences, and a gene operably encoding a repressor specific for the repressible promoter. According to the invention, selectively triggering an RNA silencing cascade against the repressor, e.g., in response to some condition, reduces the expression of the repressor protein, thereby derepressing expression of the recombinase, thereby causing excision of the excisable sequence, thus altering the sequence of the DNA molecule in which the excisable sequence was previously found. In this manner, RNA silencing of the protein coding activity of a preselected mRNA can be used to induce a genotypic change in a cell. The presence or absence of the genotypic change in the cell or within a population of such cells can be detected by standard molecular biological methods. The resulting genotypic changes present in the cell and its progeny if any can also serve as a record of exposure to the condition which caused the genotypic change to occur, for example, infection of the cell by particular virus(es) or the presence of any preselected RNA sequence in the cell.  
      Those skilled in the art will appreciate that, for a transcriptional regulatory molecule that is a protein, the time between the effective silencing of mRNA encoding the protein and the phenotypic result of that silencing will be determined by the particular protein turnover rate of that protein in a cell of interest and that such a turnover rate can also be genetically engineered, for example, by specifying the amino terminal amino acid of the protein according to the N-terminus Rule.  
      In a related embodiment of the invention, the excisable sequence element comprises an expression cassette comprising at least one gene of interest, and transcriptional regulatory elements providing for expression of the gene in a constitutive or regulated manner (developmentally, environmentally, or inducibly). In this embodiment, when recombinase expression is de-repressed, as described above, the excisable element is deleted and expression of the at least one gene of interest from the cassette is eliminated or the possibility of regulative expression of the gene is eliminated as a result of deleting the cassette.  
      Another RNA-silencing related embodiment provides introducing a series of sequences into a cell or multi-cellular organism that includes a promoter, such as a constitutively-active promoter, a transiently-active promoter or an inducible promoter, linked to a preselected gene the promoter and preselected gene being separated by a blocking sequence that is in turn bounded on either side by specific excision sequences, a repressible promoter operably linked to a gene encoding a site specific recombinase capable of recognizing the specific excision sequences, and a gene operably encoding a repressor specific for the repressible promoter. According to the invention, selectively triggering an RNA cascade against the repressor protein, e.g., in response to some condition, renders the transcripts encoding the repressor protein as a template for template directed polymerization of nucleic acids, in response to some condition, e.g., provision of a viral polymerase by an infecting virus, and reduces the expression of the repressor protein, thereby derepressing expression of the recombinase, thereby causing excision of the blocking sequence, thus providing for expression of the preselected gene. In this manner, inactivation of the protein coding activity of an mRNA via an RNA silencing cascade can be used to induce the expression of a preselected gene. In one such embodiment of the invention, the organism is a plant, the repressor protein is inhibited in response to viral infection and the preselected gene is, for example, a lethal/toxin gene or a reporter gene or an antiviral gene, for example, a gene coding for RNA silencing-inducing short RNA hairpins specific for the inhibition of viral polynucleic acid molecules or cellular polynucleic acid molecules in the cell.  
      According to the embodiments of the invention in which an mRNA transcript coding for a transcriptional regulatory protein, or a transcription-regulating RNA molecule, is targeted by RNA silencing in response to some stimuli, the stimuli may be of any sort including, but not limited to, at least one of the following variations: 
          the stimuli comprises (i) contacting the cell with a prepared, e.g., synthetic, siRNA, at least one of the strands of the siRNA being at least substantially complementary to the mRNA transcript (or transcription-regulating RNA molecule) or (ii) providing the cell with expression of such an siRNA;     the stimuli comprises contacting the cell with a short RNA hairpin molecule wherein at least one of the complementary segments of the double stranded stem structure is at least substantially complementary to the mRNA transcript (or transcription-regulating RNA molecule), or providing the cell with expression of such a molecule;     the stimuli comprises providing the cell with long dsRNA, the dsRNA having at least one strand having at least substantial complementarity with the mRNA molecule (or transcription-regulating RNA molecule);     the stimuli comprises providing the cell with long dsRNA which is processed into siRNAs in the cell, the siRNAs having at least one strand having at least substantial complementarity with the mRNA molecule (or transcription-regulating RNA molecule);     the stimuli comprises rendering the mRNA molecule (or transcription-regulating RNA molecule) initially as a template for the template directed polymerization of nucleic acids by a polymerase, wherein siRNAs or small RNA/cDNA hybrids are produced from the double stranded polymerization product, said siRNAs or small RNA/cDNA hybrids causing RNA silencing of other of the same mRNA molecules coding for the regulatory protein (or other of the same transcription-regulating RNA molecules);     the stimuli comprises expression of an RNA transcript, e.g., an mRNA transcript under control of developmentally regulated promoters and/or other transcriptional regulatory elements, (i) the cell being capable (genetically modified if necessary) of rendering the transcript, upon its expression, as a nucleic acid polymerization template to form a long dsRNA or long RNA/cDNA molecule which triggers RNA silencing, or (ii) the cell expressing a long single stranded RNA or DNA molecule at least substantially complementary to the RNA transcript, wherein, upon expression of the RNA transcript, the transcript and the expressed complementary molecule hybridize to form an at least partially double stranded molecule capable of triggering RNA silencing or (iii) the RNA transcript being itself capable of triggering RNA silencing, for example, the transcript being or comprising an RNA silencing-competent RNA hairpin;     the stimuli comprises infection of the cell by a virus and the virus characteristically forms long dsRNA which triggers RNA silencing in response to the infection, which RNA silencing comprises production of siRNAs wherein at least one strand is at least substantially complementary to the mRNA transcript for the transcriptional regulatory protein (or transcription-regulating RNA molecule), for example, as a result of genetically engineering the gene for the mRNA transcript (or transcription-regulating RNA molecule) to contain at least one region of homology to the characteristic long dsRNA region of the virus that triggers the silencing;     the stimuli comprises infection of the cell by a virus and the cell is genetically modified to render an mRNA transcript of the virus or another polynucleic acid molecule of the virus as a template for template directed polymerization of nucleic acids so that a long dsRNA or long RNA/cDNA is formed, the long molecule triggering RNA silencing in response to the infection, which RNA silencing comprises production of siRNAs wherein at least one strand is at least substantially complementary to the mRNA transcript for the transcriptional regulatory protein (or transcription-regulating RNA molecule);     and the stimuli comprises RdRp activity in a cell, for example, introduced into the cell by infection of the cell with a virus having or encoding an RdRp, and the cell is provided with an RNA transcript comprising a preselected PBS that is utilizable by the RdRp and at least one preselected sequence element upstream of the PBS that causes the direct or transitive RNA silencing against the mRNA for the transcriptional regulatory protein as a result of the formation of dsRNA by the PBS-directed utilization of the preselected sequence element part of the transcript as a template for the RdRp for example by the formation of siRNA or formation of direct RNA silencing competent product; and     the stimuli comprises the presence in a cell, e.g., by the deliberative or chance introduction in or production within the cell, of a single ssRNA or ssDNA molecule, the molecule having at least one region of known sequence, wherein the cell expresses (naturally or as a result of genetic engineering) an ssRNA or ssDNA molecule having a region of at least substantial complementarity to the region of known sequence, so that the introduced or produced single stranded molecule and the cellularly expressed single stranded molecule hybridize to form either a dsRNA molecule or RNA:DNA hybrid molecule capable of triggering RNA silencing, directly or transitively, against the mRNA molecule encoding the transcriptional regulator protein (or the transcription-regulating RNA molecule). In one example, the mRNA molecule encoding the transcriptional regulatory protein (or the transcription-regulating RNA molecule) may itself be one of one or more cellularly expressed single stranded molecules having a region of at least substantial complementarity to the region of known sequence, for example by engineering the gene encoding the mRNA to include such a region in the transcribed RNA.        

      In a related variation of the invention, the mRNA molecule encoding the transcriptional regulator protein (or the transcription-regulating RNA molecule) does not have substantial complementarity with the region of known sequence or even with any of the sequence of the introduced or produced single stranded molecule, but is transitively targeted by RNA silencing, for example, by virtue of sequence shared with or complementary to sequence in the cellularly expressed single stranded molecule that does have a region at least substantially complementarity to the introduced or produced single stranded molecule or by further degrees of transitive silencing mediated by further intermediate polynucleic molecules.  
      An example of chance introduction or production of a ssRNA or ssDNA molecule in a cell, or cell of an organisms occurs when particular viruses, virus-like agents or other environmental polynucleic acid molecules infect or otherwise enter or are produced in cells as a result of exposure to these agents in the environment.  
      In the above examples, when the sequence of at least a part of the long dsRNA or long RNA/cDNA molecule is known (such as when the trigger is a known virus or cellular transcript), the gene coding for the transcriptional regulatory protein (or transcription-regulating RNA molecule), can, if necessary, be modified to contain regions of homology to one or both of the strands of the triggering long dsRNA or long RNA/cDNA molecule so that the siRNA in conjunction with RISC will target these regions using siRNAs formed from the long double stranded molecules. Conversely, if the polynucleic acid molecule for which it is desired to trigger RNA silencing upon expression of the molecule is encoded by a cellular gene (endogenous or transgene), the sequence of the gene for this molecule can, if necessary, be modified to comprise regions of homology to the mRNA transcript for the transcriptional regulatory protein (or to the transcription-regulating RNA molecule) so that upon the polynucleic acid molecule becoming double stranded it is processed to render siRNAs wherein at least one strand is at least substantially complementary to the target repressor protein transcript (or transcription-regulating RNA molecule).  
      Where RNA silencing is operable, a first molecule that will be targeted to produce siRNAs may be modified to induce RNA silencing-against a selected downstream molecule by modifying the first molecule (e.g. by modifying the gene expressing the molecule) to comprise sequence that will form siRNA strands having homology with or being complementary to the sequence of the selected downstream molecule. Alternatively, or in addition, a selected molecule can be rendered as a downstream target of an RNA silencing cascade triggered by the first molecule by modifying the second molecule (e.g. by modifying the gene expressing the molecule) so that it comprises at least one sequence element having homology with or being complementary to the sequence of the first molecule that forms siRNAs. For an mRNA molecule, such modification may be made, for example, in the 5′ untranslated region, the 3′ untranslated region, in naturally occurring or genetically engineered intronic sequences, and/or even in the protein coding sequence so long as any desired protein coding activity and corresponding protein activity is not negatively impacted to a substantial extent.  
      Transitive RNA silencing embodiments corresponding to the direct RNA silencing embodiments of the invention can also be provided, when desired, according to the invention. For example, those skilled in the art will readily appreciate that, in organisms and cell types where transitive RNA silencing is operative, for example plants, at least one intermediate polynucleic acid molecule may be used to indirectly mediate the transfer of the RNA silencing signal, via siRNAs, from an initial, or otherwise “upstream,” double-stranded, long triggering molecule to the target mRNA transcript of the transcriptional regulatory protein. In this case the intermediate molecule will have complementary sequences to at least one siRNA strand produced from the initial molecule, thereby rendering it a target for siRNAs formed from the initial molecule, and at least one other sequence, generally in the three-prime direction with respect to the primer strand of said siRNA, the other sequence being complementary or having homology to the ultimate target RNA transcript in question so that formation of a long dsRNA from the intermediate molecule causes the formation of siRNAs wherein at least one strand is complementary to the ultimate target. Thus, when it is known that a first molecule will be subject to RNA silencing, the silencing event can be transitively targeted to one or more selected other molecules by providing the cell with expression of one or more intermediate molecules.  
      In cells or organisms in which the siRNA in conjunction with RISC or other factors functions to prime the target molecule and induce template directed polymerization of nucleic acids using the target as a template, the introduction of the regions of homology is an introduction of a PBS according to the invention and, likewise, providing an siRNA is an example of providing a primer molecule.  
      The invention also encompasses the case where the siRNA in conjunction with RISC or other factors does not induce, or is not capable of inducing template directed polymerization of nucleic acid molecules but nevertheless binds to the target and optionally causes nuclease activity against the target.  
      As further discussed herein, when the condition triggering the polymerase-mediated inactivation of the repressor is the expression of a preselected RNA transcript (or any RNA transcript having a preselected sequence) in the cells of a multi-cellular organism according to normal developmental regulation, the recombinase derepression embodiment of the invention can be used to detect expression of the preselected RNA transcript generally and to trace the cellular lineage of expression of the preselected RNA transcript, both visibly, for example by using GFP or a derivative as a recombinase-derepressible gene, or by genetic histological analysis.  
      Viral Infection Detection Systems  
      The invention provides a number of polymerase mediated viral infection diagnostic systems and methods.  
      A biological assay for the presence or absence of particular viruses in a sample or in the environment in general is provided according to the invention by modifying cells to express cellular transcripts which have reporter activity and which are operably-linked to the viral polymerase activity when the polymerase is provided by infection of the cell, so that the reporter activity is inhibited by the viral polymerases of the particular infecting virus(es). This viral infection detection system may, for example, be employed in a laboratory assay format utilizing test cells, i.e., a test cell line subjected to samples. These cells may be of the type or derived from the type of cells that are naturally infected by the particular viruses for which the assay is developed. Alternatively, cells which are not normally susceptible to infection by the particular virus(es) for which it is desired to develop assay cells, may be engineered to have the appropriate susceptibility to infection. This can be achieved by various methods known in the art such as, but not limited to, engineering the subject cells to express a virus receptor protein or receptor glycoside which is otherwise missing from the subject cell or expressed on at a low level by the cell. Those skilled in the art will understand that the method will be tailored to the specific virus and cell type in question.  
      Multi-cellular organisms can also be genetically modified to embody this type of viral detection system generally, or in one or more selected tissues or cell types. In one embodiment of the invention, a plant is engineered to embody the viral detection system. A suitable reporter gene for a plant can be, for example, a gene conferring a particular pigmentation or coloration, the absence of the expression of the gene being readily discernable. In this manner, substantially real-time monitoring of pathogen activity in a field of crops can be accomplished and appropriate steps to limit further crop damage can then taken. In another embodiment of the invention, animals such as, but not limited to, livestock can be genetically modified to similarly embody the viral detection system in one or more tissues and hence report the presence of viral infection.  
      In one method of the invention, agricultural crops in the same field or commonly raised animals generally embody a viral infection detection system according to this or any viral infection detection embodiment of the invention. In this manner, real-time monitoring of pathogen activity can be accomplished and appropriate steps to limit further damage, such as destruction of the affected section of crops or segregation of affected livestock, can then taken. In another method according to the invention “detection” organisms embodying a viral infection detection system according to the invention are provided within a field of agricultural crops or among a group of commonly raised livestock that generally do not embody such a detection system.  
      One embodiment of the invention provides a diagnostic method, and cell compositions therefore, for determining the presence or absence of a pre-specified virus in a sample comprising the steps of: providing tests cells genetically engineered so that a preselected reporter template molecule expressed within the cells becomes a functional template of a template directed nucleic acid polymerase as a result of infection of the cells by virus present in the samples; contacting a sample potentially containing virus with the test cells; and determining whether the discernable characteristic-conferring activity of the reporter-templates of the test cells is modulated, thereby indicating presence of the virus in the sample.  
      A related diagnostic embodiment comprises performing the steps in parallel with the test sample and a negative control sample not containing the virus, and comparing the result obtained using the test sample to the results obtained from the negative control sample to determine whether the test sample contains the virus. Still another embodiment of the diagnostic method comprises performing the steps in parallel with the test sample and a positive control sample containing a control virus to determine whether the test sample contains the virus. For safety, when the virus for which testing is being performed is a pathogenic virus of humans, other animals or plants, the virus used as the positive control need not actually be pathogenic but merely needs to resemble the actual pathogenic virus with respect to mimicking its performance in the assay. In a still further related embodiment, the diagnostic method is performed using the test sample and both the positive and negative control samples.  
      The discernable characteristic-conferring activity of a reporter template may be of any detectable sort including, but not limited to, directly or indirectly repressing the expression of another gene that has reporter activity by, for example, virtue of coding for a protein having reporter or selectable marker activity as known in the art, whereby said repression is relieved as a result of the reporter template being made to serve as a template upon viral infection.  
      The invention also provides diagnostic methods and compositions of matter that utilize the double strand mediated RNA silencing embodiments described above in which the presence of viral nucleic acid polymerase, such as an RdRp, or a viral polynucleic acid molecule such a s a viral RNA molecule serves as the stimuli triggering RNA silencing against a transcriptional regulatory molecule, such as a functional mRNA encoding a transcriptional regulatory protein or a transcription regulating RNA, that directly or indirectly controls the expression of a preselected gene product that confers a discernable characteristic, such as a reporter activity. A diagnostic method and system is thus obtained according to the invention by providing “test” cells embodying at least one of these embodiments of the invention and contacting the cells with tests samples that may contain a virus capable of serving as the stimuli to trigger an RNA silencing response against the transcriptional regulatory molecule, thus potentially affecting the discernable characteristic. A change in the extent of the discernable characteristic, such as reporter activity, is indicative of the presence of the virus or viral molecules in the test cells. As described before, one or more controls may be run in parallel. In one variation, the test cells are comprised with an organism such as a plant. In a related embodiment, such test cells or one or more organisms comprising such cells are exposed to the environment, for example by cultivation in the environment, and infection of the organism or one or more cells of the organism by a virus competent to affect the extent of the discernable characteristic, as described, or the lack of such an infection, is determined by characterizing the extent of the discernible characteristic conferred.  
      The test cells of the diagnostic embodiments of the invention may be cultured in any appropriate format, including, but not limited to, liquid suspension culture or culture on a surface submerged in growth media or on a surface of growth media. Further, the steps of the diagnostic method may, for example, be performed in one or more of any sort of appropriate tube, well plate, vessel or container as known in the art.  
      It should be understood that in the performance of the steps of the diagnostic method, changes in the reporter activity of the tests cells caused by virus can include the change caused by the original virus particles in the sample and also progeny virus which propagates from this original virus. Thus, according to the invention, after treating the tests cells with a sample, the mixture can optionally be incubated for varying amounts of time to allow for viral propagation to occur. In another embodiment, virus that may exist in a sample can be propagated in other cells before testing to amplify the amount of virus in the original sample. The cells used for propagation of the virus in this embodiment need not be test cells, but can be any sort of cells permissive for propagation of the virus. In a related embodiment, the propagator cells, having been incubated with the original sample, are separated from the putatively-propagated virus containing mix/culture and the cell-free mix is then introduced to the test cells.  
      The cell-based diagnostic assay embodiments of the invention can benefit in sensitivity by the use of test cells which are highly prone to infection by the subject virus(es) for which the diagnostic assay is designed. Accordingly one embodiment of the invention provides that the test cells are mutated and selected to be more highly prone to infection by the subject virus(es). Such mutation may, for example, be random in response to a mutagenic treatment followed by selection or may involve genetic engineering. For example, a cell being designed for use as a test cell can be genetically engineered to express a higher level of the receptor that the subject virus(es) uses to enter the cell.  
      Examples of types of viruses for which the embodiments of the invention are generally applicable  
      Tables 1-10 illustrate various categories of viruses and virus-like polynucleic acid molecules for which the diagnostic and viral resistance embodiments of the invention can be employed. Template-directed polymerases of, or used by, these viruses are examples of polymerases that can be used for polymerase-mediated gene regulation according to the invention. Each of the tables shows the order, family [subfamily] and genus of viruses for which the present invention can be employed. In addition, at least one type species example is provided for each genus listed. Tables 1-10 are arranged according to the following categories: Table 1—dsDNA viruses; Table 2—ssDNA viruses; Table 3—DNA reverse transcribing viruses; Table 4—RNA reverse transcribing viruses; Table 5—dsRNA Viruses; Table 6—negative-sense ssRNA viruses; Table 7—positive-sense ssRNA viruses; Table 8—naked RNA viruses; Table 9—viroids; and Table 10—subviral agents. It should be understood that the terms “virus” and “viruses” as used in the accompanying description and claims refers to viruses and virus-like polynucleic acids, as exemplified in Tables 1-10.  
      Examples of plants and their viruses for which the embodiments of the invention are applicable  
      The following list illustrates examples of various crop plants and their respective common viruses for which the diagnostic and viral resistance methods of the invention can be embodied: alfalfa—alfalfa mosaic, lucerene transient streak, alfalfa latent; barley—barley stripe, barley yellow dwarf, barley yellow streak, barley yellow streak mosaic, brome mosaic, oat blue dwarf; bean—bean common mosaic virus, bean yellow mosaic virus, beet curly top, cucumber mosaic virus, pea enation mosaic; beet—beet cryptic virus 1, beet cryptic virus 2, beet cryptic virus 3, beet curly top, beet mosaic, beet necrotic yellow vein, beet pseudoyellows, beet soilborne mosaic, beet western yellows, beet yellows, brassicas—cauliflower mosaic virus, turnip mosaic; capsicum species—alfalfa mosaic, beet curly top, cucumber mosaic, potato virus x, potato virus y, tobacco etch, tobacco mosaic, tobacco rattle, tomato spotted wilt; carrots—alfalfa mosaic, carrot mottle, carrot red leaf, carrot thin leaf, carrot mottley dwarf; chrysanthemum species—chrysanthemum aspenny, chrysanthemum mosaic, chrysanthemum virus b, tomato aspermy, impatiens necrotic spot; corn—maize dwarf, maize chlorotic dwarf, maize chlorotic mottle, maize dwarf, maize raydo fino, maize stripe, maize white line mosaic; cotton—cotton leaf crumple; cucumis species—alfalfa mosaic, beet curly top, cucumber mosaic virus, lettuce infectious yellows, papaya ringspot virus, tomato spotted wilt, watermelon mosaic virus 2, squash mosaic virus, zucchini yellow mosaic; cucurbita species—beet curly top, cucumber mosaic virus, papaya ringspot virus, watermelon mosaic virus 2, squash mosaic virus, squash leaf curl, tomato spotted wilt; gladiolus—bean common mosaic virus, lily symptomless virus; lettuce—alfalfa mosaic, beet western yellows, cucumber mosaic, sowthisltle yellow vein, tobacco rattle, tobacco ringspot, tomato spotted wilt, turnip mosaic; papaya—papaya ringspot virus; pea—bean leaf roll, bean yellow mosaic virus, pea enation mosaic virus, tomato spotted wilt, pea seedbome mosaic, pea streak; peanut—peanut mottle, peanut stripe, peanut stunt, tomato spotted wilt; pepper—cucumber mosaic virus, papaya ringspot virus, watermelon mosaic virus 2, squash mosaic virus, pepper cryptic virus 1, pepper mild mottle, pepper mottle, pepper veinal mottle; potatoes—potato leaf roll, potato virus y, potato virus x, potato virus a, potato virus m, potato virus s, tobacco rattle, tomato spotted wilt; rice—rice hoja blanca; sorghum—maize dwarf mosaic, sugarcane mosaic, maize chlorotic dwarf; soybean—bean pod mottle, cowpea chlorotic mottle, peanut mottle, soybean dwarf, soybean mosaic, tobacco ringspot, tobacco streak, bean yellow mosaic, cowpea severe, peanut stripe, tobacco mosaic; strawberry—tomato ringspot, strawberry chlorosis, strawberry crinkle, strawberry latent, strawberry mottle, strawberry vein banding; sugar beets—beet curly top, beet cryptic virus 1, beet cryptic virus 2, beet cryptic virus 3, beet mosaic, beet necrotic yellow vein, beet pseudoyellows, beet soilborne mosaic, beet western yellows, beet yellows; sweet potato—sweet potato feathery mottle; tobacco—tobacco mosaic, potato virus y, tomato spotted wilt, tobacco etch, tobacco vein mottling, alfalfa mosaic; tomatoes—alfalfa mosaic, cucumber mosaic, beet curly top, tobacco etch, potato virus y, tomato bushy stunt, tomato mosaic, tomato spotted wilt, tomato ringspot, tomato mottle; and wheat—agropyron mosaic, barley stripe, barley yellow dwarf, barley yellow streak, barley yellow streak mosaic.  
     Examples of Animals (or the Cells Thereof) and Their Viruses for Which the Embodiments of the Invention are Applicable  
      Viral pathogenic infection of agricultural animals poses a significant problem for animal health and food production. The present invention provides methods for producing transgenic livestock and other transgenic agricultural animals that are resistant to prespecified viral pathogens. Accordingly, diagnostic and viral resistance embodiments of the invention can be employed for agricultural animals such as, but not limited to, bovids (cattle; sheep; goats, etc.), swine, fowl (chicken; quail; turkey, duck, goose, etc.); fishes, crustaceans (shrimp, crayfish, lobster, crab, etc.) and mollusca (oyster, mussel, clam, etc.).  
      Tables 11A and 11B show examples of various animals and their common viral pathogenic diseases for which the diagnostic and viral resistance methods of the invention can be embodied.  
      Aquacultured (maricultured) species have heretofore been particularly susceptible to rapid and dramatic loss as a result of viral pathogens, in part due to the typically high density of the culture conditions.  
      Fish viruses for which the embodiments of the invention are applicable include, but are not limited to: rhabdoviruses such as spring viremeia of carp virus; bimaviridae infections such as pancreatic necrosis virus; iridoviridae such as fish lymphocytes disease virus; salmonids with infectious hematopoietic necrocosis (HIN); viral hemorrhagic septicemia (VHS) virus; marine viral haemorrhagic septicaemia (VHS), a disease closely related to VHS known from freshwater rainbow trout farming; largemouth bass virus (LMBV); lymphocystis, a viral disease in common dab; infectious salmon anemia; Koi Herpes Virus (KHV); and Monodon baculo virus (MBV).  
      Shrimp viruses for which the embodiments of the invention are applicable include, but are not limited to, Infectious Hyposdermal and Hematopoietic Necrosis Virus (IHHNV); Taura Syndrome Virus (TSV); White Spot Syndrome Virus (WSSV); and Yellow Head Virus (YHV).  
      The genetic modification of animals to impart viral resistance against preselected viruses can also provide benefits for human health in the case of viral zoonoses, i.e., viral diseases that are transmitted to humans from animals. For example, it is well established that swine and avians, e.g., ducks, are hosts to influenza viruses and transmit such viruses to each other and to humans. Other viral pathogens are transmissible to humans from insects. According to one embodiment of the invention, genetically modified pigs embodying resistance to influenza virus according to the invention are raised, thereby reducing zoonetic transmission of the disease to the human population.  
      The techniques used for producing genetically-engineered cells and transgenic multi-cellular organisms according to the invention are routine in the art and are, accordingly, only briefly described herein.  
      As referred to herein, a genetically modified cell or multi-cellular organism refers to a cell or organism that has been genetically engineered to embody genetic sequences required for the functioning of the invention, or which are derived from such a cell or organism and comprise the introduced change(s). Genetically modified cells and genetically -modified organisms according to the invention include cells and organisms genetically engineered to contain transgenes and/or to have genetic sequence alterations including deletions, or which are derived from such a cell or organism and comprise the introduced change(s). Cells transiently transformed with DNA or RNA constructs are also within the scope of the invention.  
      A variety of routine methods for introducing DNA into cells for the introduction of transgenes to the cells and/or to effectuate other genetic changes in the cells are well established. Predetermined deletions and other sequence changes of preselected genes and other genetic sequences in a cell can be performed using homologous recombination techniques as known in the art.  
      Transgenic animals are animals having cells that contain a transgene, wherein the transgene was introduced into the animal or an ancestor of the animal at a prenatal, e.g., an embryonic, stage. Non-human animals into which transgenes or other discrete genetic changes can be introduced by genetic engineering techniques known in the art include, but are not limited to, mice, goats, sheep, pigs, cows and other domestic farmi animals, as well as fish, birds, and crustaceans and insects. A transgenic animal can be created, for example, by introducing a nucleic acid sequence encoding a protein of interest (typically linked to appropriate regulatory elements, such as a constitutive or tissue-specific promoter and/or other regulatory elements) into the male pronuclei of a fertilized oocyte, e.g., by microinjection, and allowing the oocyte to develop in a pseudopregnant female foster animal. An alternative method comprises introducing a desired DNA into the genome an embryonic stem cell and regenerating the organism by introducing the modified stem cell into a developing early-stage embryo. A transgenic founder animal can be used to breed additional animals carrying the transgene.  
      Techniques for transforming a wide variety of higher plant species are well established and described in the technical and scientific literature. A DNA sequence coding for a desired gene product can be combined with transcriptional and translational initiation regulatory sequences that will direct the transcription of the sequence from the gene in the intended tissues of the transformed plant.  
      For example a plant promoter fragment may be employed which will direct expression of the gene in all or substantially all tissues of a regenerated plant. Such promoters are referred to herein as “constitutive” promoters and are active under most environmental conditions and states of development or cell differentiation. Examples of constitutive promoters include the cauliflower mosaic virus (CaMV) 35S transcription initiation region, the 1′- or 2′-promoter derived from T-DNA of  Agrobacterium tumefaciens,  and other transcription initiation regions from various plant genes known to those of skill.  
      Alternatively, the plant promoter may direct expression of a nucleic acid of the invention in a specific tissue, organ or cell type (i.e. tissue-specific promoters) or may be otherwise under more precise environmental or developmental control (e.g., inducible promoters). Examples of environmental conditions that may effect transcription by inducible promoters include anaerobic conditions, elevated temperature, the presence of light, or application of chemicals such as hormones. Exemplary promoters for this purpose include promoters from glucocorticoid receptor genes (Aoyama and Chua, Plant J 11:605-12 (1997)). Tissue-specific promoters may only promote transcription within a certain time frame of developmental stage within that tissue. Other tissue specific promoters may be active throughout the life cycle of a particular tissue.  
      Techniques for the production of transgenic plants are well established. For example, the DNA construct comprising a transgene may be introduced directly into the genomic DNA of the plant cell using techniques such as electroporation and microinjection of plant cell protoplasts, or the DNA constructs can be introduced directly to plant tissue using ballistic methods, such as DNA particle bombardment, or Agrobacteriurn tumefaciens-mediated transformation techniques, including disarming and use of binary vectors, are well described in the scientific literature. Transformed plant cells that are derived by any of the above transformation techniques can be cultured to regenerate a whole plant that possesses the transformed genotype and thus the desired phenotype such as increased seed mass. Regeneration can also be obtained from plant callus, explants, organs, or parts thereof.  
      It should be understood that the above descriptions are meant to be illustrative. With respect to its cell-based embodiments, the invention is not limited by the subcellular compartment(s) in which its components are processed and ultimately function. Many embodiments within the scope of the invention may be apparent to those of skill in the art upon reviewing the above descriptions. The scope of the invention should, therefore, be determined with reference to the claims, along with the full scope of equivalents to which such claims are entitled.  
               TABLE 1                          dsDNA Viruses                                 Family       Type Species       Order    [Subfamily]   Genus   Example               Caudovirales   Myoviridae   “T4-like viruses”   Enterobacteria phage                   T4               “P1-like viruses”   Enterobacteria phage                   P1               “P2-like viruses”   Enterobacteria phage                   P2               “Mu-like viruses”   Enterobacteria phage                   Mu               “SPO1-like viruses”   Bacillus phage SPO1               “ΦH-like viruses”   Halobacterium virus                   ΦH           Siphoviridae   “λ-like viruses”   Enterobacteria phage λ               “T1-like viruses”   Enterobacteria phage                   T1               “T5-like viruses”   Enterobacteria phage                   T5               “c2-like viruses”   Lactococcus phage                   c2               “L5-like viruses”   Mycobacterium                   phage L5               “ψM1-like viruses”   Methanobacterium                   ψM1           Podoviridae   “T7-like viruses”   Enterobacteria phage                   T7               “φ29-like viruses”   Bacillus phage φ29               “P22-like viruses”   Enterobacteria phage                   P22           Rudiviridae   Rudivirus   Sulfolobus virus                   SIRV1           Tectiviridae   Tectivirus   Enterobacteria phage                   PRD1           Corticoviridae   Corticovirus   Alteromonas phage                   PM2           Lipothrixviridae   Lipothrixvirus   Thermoproteus virus 1           Plasmaviridae   Plasmavirus   Acholeplasma phage                   L2           Fuselloviridae   Fusellovirus   Sulfolobus virus                   SSV1           Phycodnaviridae   Chlorovirus   Paramecium bursaria                   Chlorella virus 1               Prasinovirus   Micromonas pusilla                   virus SP&#39;1               Prymnesiovirus   Chrysochromulina                   brevifilum virus                   PW1               Phaeovirus   Ectocarpus siliculosis                   virus 1               “Sulfolobus SNDV-   Sulfolobus virus               like viruses”   SNDV           Poxviridae   Orthopoxvirus   Vaccinia virus            [Chordopoxvirinae]               Parapoxvirus   Orf virus               Avipoxvirus   Fowlpox virus               Capripoxvirus   Sheeppox virus               Leporipoxvirus   Myxoma virus               Suipoxvirus   Swinepox virus               Molluscipoxvirus   Molluscum                   contagiosum virus               Yatapoxvirus   Yaba monkey tumor                   virus            [Entomopoxvirinae]   Entomopoxvirus A   Melolontha                   melolontha                   entomopoxvirus               Entomopoxvirus B   Amsacta moorei                   entomopoxvirus               Entomopoxvirus C   Chironomus luridus                   entomopoxvirus           Iridoviridae   Iridovirus   Invertebrate                   iridescent virus 6               Chloriridovirus   Invertebrate                   iridescent virus 3               Ranavirus   Frog virus 3               Lymphocystivirus   Lymphocystis                   disease virus 1           Polydnaviridae   Ichnovirus   Campoletis                   sonorensis ichnovirus               Bracovirus   Cotesia melanoscela                   bracovirus           Herpesviridae   Ictalurivirus (was   Ictalurid herpesvirus 1               “Ictalurid herpes-like               viruses”)            [Alphaherpesvirinae]   Simplexvirus   Human herpesvirus 1               Varicellovirus   Human herpesvirus 3               Mardivirus (was   Gallid herpesvirus 2               “Marek&#39;s disease-like               viruses”               Iltovirus (was   Gallid herpesvirus 1               “Infectious laryngotracheitis-               like               viruses”)            [Betaherpesvirinae]   Cytomegalovirus   Human herpesvirus 5               Muromegalovirus   Murid herpesvirus1               Roseolovirus   Human herpesvirus 6            [Gammaherpesvirinae]   Lymphocryptovirus   Human herpesvirus 4               Rhadinovirus   Saimiriine                   herpesvirus 2           Polyomaviridae   Polyomavirus   Simian virus 40           Papillomaviridae   Papillomavirus   Cottontail rabbit                   papillomavirus           Adenoviridae   Mastadenovirus   Human adenovirus C               Aviadenovirus   Fowl adenovirus A               Atadenovirus   Ovine adenovirus D               Siadenovirus   Turkey adenovirus B           Ascoviridae   Ascovirus   Spodoptera                   frugiperda ascovirus           Baculoviridae   Nucleopolyhedrovirus   Autographa                   californica                   nucleopolyhedrovirus               Granulovirus   Cydia pomonella                   granulovirus           Nimaviridae   Whispovirus   White spot syndrome                   virus 1           Asfarviridae   Asfivirus   African swine fever                   virus               Rhizidiovirus   Rhizidiomyces virus                  
 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                   
               
               
                 ssDNA Viruses 
               
            
           
           
               
               
               
               
            
               
                   
                 Family 
                   
                 Type Species 
               
               
                 Order 
                  [Subfamily] 
                 Genus 
                 Example 
               
               
                   
               
               
                   
                 Inoviridae 
                 Inovirus 
                 Enterobacteria 
               
               
                   
                   
                   
                 phage M13 
               
               
                   
                   
                 Plectrovirus 
                 Acholeplasma 
               
               
                   
                   
                   
                 phage MV-L51 
               
               
                   
                 Microviridae 
                 Microvirus 
                 Enterobacteria 
               
               
                   
                   
                   
                 phage φX174 
               
               
                   
                   
                 Spiromicrovirus 
                 Spiroplasma phage 4 
               
               
                   
                   
                 Bdellomicrovirus 
                 Bdellovibrio phage 
               
               
                   
                   
                   
                 MAC1 
               
               
                   
                   
                 Chlamydiamicrovirus 
                 Chlamydia phage 1 
               
               
                   
                 Geminiviridae 
                 Mastrevirus 
                 Maize streak virus 
               
               
                   
                   
                 Curtovirus 
                 Beet curly top virus 
               
               
                   
                   
                 Begomovirus 
                 Bean golden mosaic 
               
               
                   
                   
                   
                 virus - Puerto Rico 
               
               
                   
                 Circoviridae 
                 Circovirus 
                 Porcine circovirus 
               
               
                   
                   
                 Gyrovirus 
                 Chicken anaemia 
               
               
                   
                   
                   
                 virus 
               
               
                   
                 Nanoviridae 
                 Nanovirus 
                 Subterranean clover 
               
               
                   
                   
                   
                 stunt virus 
               
               
                   
                   
                 Babuvirus 
                 Babana bunchy top 
               
               
                   
                   
                   
                 virus 
               
               
                   
                 Parvoviridae 
                 Parvovirus 
                 Murine Minute 
               
               
                   
                  [Parvovirinae] 
                   
                 virus 
               
               
                   
                   
                 Erythrovirus 
                 B19 virus 
               
               
                   
                   
                 Dependovirus 
                 Adeno-associated 
               
               
                   
                   
                   
                 virus 2 
               
               
                   
                  [Densovirinae] 
                 Densovirus 
                 Junonia coenia 
               
               
                   
                   
                   
                 densovirus 
               
               
                   
                   
                 Iteravirus 
                 Bombyx mori 
               
               
                   
                   
                   
                 densovirus 
               
               
                   
                   
                 Brevidensovirus 
                 Aedes aegypti 
               
               
                   
                   
                   
                 densovirus 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                   
               
               
                 DNA Reverse Transcribing Viruses 
               
            
           
           
               
               
               
               
            
               
                   
                   
                   
                 Type Species 
               
               
                 Order 
                 Family 
                 Genus 
                 Example 
               
               
                   
               
               
                   
                 Pseudoviridae 
                 Pseudovirus 
                 Saccharomyces 
               
               
                   
                   
                   
                 cerevisiae Ty1 virus 
               
               
                   
                   
                 Hemivirus 
                 Drosophila 
               
               
                   
                   
                   
                 melanogaster copia 
               
               
                   
                   
                   
                 virus 
               
               
                   
                 Metaviridae 
                 Metavirus 
                 Saccharomyces 
               
               
                   
                   
                   
                 cerevisiae Ty3 virus 
               
               
                   
                   
                 Errantivirus 
                 Drosophila 
               
               
                   
                   
                   
                 melanogaster gypsy 
               
               
                   
                   
                   
                 virus 
               
               
                   
                 Hepadnaviridae 
                 Orthohepadnavirus 
                 Hepatitis B virus 
               
               
                   
                   
                 Avihepadnavirus 
                 Duck hepatitis B 
               
               
                   
                   
                   
                 virus 
               
               
                   
                 Caulimoviridae 
                 Badnavirus 
                 Commelina yellow 
               
               
                   
                   
                   
                 mottle virus 
               
               
                   
                   
                 Caulimovirus 
                 Cauliflower mosaic 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Tungrovirus (was 
                 Rice tungro 
               
               
                   
                   
                 “Rice tungro bacilliform- 
                 bacilliform virus 
               
               
                   
                   
                 like viruses”) 
               
               
                   
                   
                 Soymovirus (was 
                 Soybean chlorotic 
               
               
                   
                   
                 “Soybean chlorotic 
                 mottle virus 
               
               
                   
                   
                 mottle-like viruses”) 
               
               
                   
                   
                 Cavemovirus (was 
                 Cassava vein 
               
               
                   
                   
                 “Cassava vein 
                 mosaic virus 
               
               
                   
                   
                 mosaic-like 
               
               
                   
                   
                 viruses”) 
               
               
                   
                   
                 Petuvirus (was 
                 “Petunia vein 
               
               
                   
                   
                 “Petunia vein 
                 clearing virus 
               
               
                   
                   
                 clearing-like 
               
               
                   
                   
                 viruses”) 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                   
               
               
                 RNA Reverse Transcribing Viruses 
               
            
           
           
               
               
               
               
            
               
                   
                 Family 
                   
                 Type Species 
               
               
                 Order 
                  [Subfamily] 
                 Genus 
                 Example 
               
               
                   
               
               
                   
                 Retroviridae 
                 Alpharetrovirus 
                 Avian leucosis virus 
               
               
                   
                  [Orthoretrovirinae] 
               
               
                   
                   
                 Betaretrovirus 
                 Mouse mammary 
               
               
                   
                   
                   
                 tumour virus 
               
               
                   
                   
                 Gammaretrovirus 
                 Murine leukeamia 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Deltaretrovirus 
                 Bovine leukaemia 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Epsilonretrovirus 
                 Walleye dermal 
               
               
                   
                   
                   
                 sarcoma virus 
               
               
                   
                   
                 Lentivirus 
                 Human 
               
               
                   
                   
                   
                 immunodeficiency 
               
               
                   
                   
                   
                 virus 1 
               
               
                   
                  [Spumaretrovirinae] 
                 Spumavirus 
                 Simian foamy virus 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                   
               
               
                 dsRNA Viruses 
               
            
           
           
               
               
               
               
            
               
                   
                   
                   
                 Type Species 
               
               
                 Order 
                 Family 
                 Genus 
                 Example 
               
               
                   
               
               
                   
                 Cystoviridae 
                 Cystovirus 
                 Pseudomonas phage 
               
               
                   
                   
                   
                 ψ6 
               
               
                   
                 Reoviridae 
                 Orthoreovirus 
                 Mammalian 
               
               
                   
                   
                   
                 orthoreovirus 
               
               
                   
                   
                 Orbivirus 
                 Bluetongue virus 
               
               
                   
                   
                 Rotavirus 
                 Rotavirus A 
               
               
                   
                   
                 Coltivirus 
                 Colorado tick fever 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Seadornavirus 
                 Kadipiro virus 
               
               
                   
                   
                 Aquareovirus 
                 Aquareovirus A 
               
               
                   
                   
                 Cypovirus 
                 Cypovirus 1 
               
               
                   
                   
                 Entomoreovirus 
                 Hyposoter exiguae 
               
               
                   
                   
                   
                 reovirus 
               
               
                   
                   
                 Fijivirus 
                 Fiji disease virus 
               
               
                   
                   
                 Phytoreovirus 
                 Rice dwarf virus 
               
               
                   
                   
                 Oryzavirus 
                 Rice ragged stunt 
               
               
                   
                   
                   
                 virus 
               
               
                   
                 Birnaviridae 
                 Aquabirnavirus 
                 Infectious 
               
               
                   
                   
                   
                 pancreatic necrosis 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Avibirnavirus 
                 Infectious bursal 
               
               
                   
                   
                   
                 disease virus 
               
               
                   
                   
                 Entomobirnavirus 
                 Drosophila X virus 
               
               
                   
                 Totiviridae 
                 Totivirus 
                 Saccharomyces 
               
               
                   
                   
                   
                 cerevisiae virus L-A 
               
               
                   
                   
                 Giardiavirus 
                 Giardia lamblia 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Leishmaniavirus 
                 Leishmania RNA 
               
               
                   
                   
                   
                 virus 1-1 
               
               
                   
                 Chrysoviridae 
                 Chrysovirus 
                 Penicillium 
               
               
                   
                   
                   
                 chrysogenum virus 
               
               
                   
                 Partitiviridae 
                 Partitivirus 
                 Atkinsonella 
               
               
                   
                   
                   
                 hypoxylon virus 
               
               
                   
                   
                 Alphacryptovirus 
                 White clover cryptic 
               
               
                   
                   
                   
                 virus 1 
               
               
                   
                   
                 Betacryptovirus 
                 White clover cryptic 
               
               
                   
                   
                   
                 virus 2 
               
               
                   
                 Hypoviridae 
                 Hypovirus 
                 Cryphonectria 
               
               
                   
                   
                   
                 hypovirus 1-EP713 
               
               
                   
                   
                 Varicosavirus 
                 Lettuce big-vein 
               
               
                   
                   
                   
                 virus 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                   
               
               
                 Negative Sense ssRNA Viruses 
               
            
           
           
               
               
               
               
            
               
                 Order 
                 Family 
                 Genus 
                 Type Species Example 
               
               
                   
               
               
                 Mononegavirales 
                 Paramyxoviridae 
                 Respirovirus 
                 Sendai virus 
               
               
                   
                  [Paramyxovirinae] 
               
               
                   
                   
                 Morbillivirus 
                 Measles virus 
               
               
                   
                   
                 Rubulavirus 
                 Mumps virus 
               
               
                   
                   
                 Henipavirus 
                 Hendra virus 
               
               
                   
                   
                 Avulavirus 
                 Newcastle disease 
               
               
                   
                   
                   
                 virus 
               
               
                   
                  [Pneumovirinae] 
                 Pneumovirus 
                 Human respiratory 
               
               
                   
                   
                   
                 syncytial virus 
               
               
                   
                   
                 Metapneumovirus 
                 Avian pneumovirus 
               
               
                   
                 Rhabdoviridae 
                 Vesiculovirus 
                 Vesicular stomatitis 
               
               
                   
                   
                   
                 Indiana virus 
               
               
                   
                   
                 Lyssavirus 
                 Rabies virus 
               
               
                   
                   
                 Ephemerovirus 
                 Bovine ephemeral 
               
               
                   
                   
                   
                 fever virus 
               
               
                   
                   
                 Cytorhabdovirus 
                 Lettuce necrotic 
               
               
                   
                   
                   
                 yellows virus 
               
               
                   
                   
                 Nucleorhabdovirus 
                 Potato yellow 
               
               
                   
                   
                   
                 dwarf virus 
               
               
                   
                   
                 Novirhabdovirus 
                 Infectious 
               
               
                   
                   
                   
                 hematopoietic 
               
               
                   
                   
                   
                 necrosis virus 
               
               
                 Mononegavirales 
                 Filoviridae 
                 Marburgvirus (was 
                 Lake Victoria 
               
               
                   
                   
                 “Marburg-like 
                 marburgvirus (was 
               
               
                   
                   
                 viruses”) 
                 Marburgvirus) 
               
               
                   
                   
                 Ebolavirus (was 
                 Zaire ebolavirus 
               
               
                   
                   
                 “Ebola-like 
                 (was Zaire Ebola 
               
               
                   
                   
                 viruses”) 
                 virus) 
               
               
                   
                 Bornaviridae 
                 Bornavirus 
                 Borna disease virus 
               
               
                   
                 Orthomyxoviridae 
                 Influenzavirus A 
                 Influenza A virus 
               
               
                   
                   
                 Influenzavirus B 
                 Influenza B virus 
               
               
                   
                   
                 Influenzavirus C 
                 Influenza C virus 
               
               
                   
                   
                 Thogotovirus 
                 Thogoto virus 
               
               
                   
                   
                 Isavirus 
                 Infectious salmon 
               
               
                   
                   
                   
                 anemia virus 
               
               
                   
                 Bunyaviridae 
                 Orthobunyavirus 
                 Bunyamwera virus 
               
               
                   
                   
                 Hantavirus 
                 Hantaan virus 
               
               
                   
                   
                 Nairovirus 
                 Dugbe virus 
               
               
                   
                   
                 Phlebovirus 
                 Rift Valley fever 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Tospovirus 
                 Tomato spotted 
               
               
                   
                   
                   
                 wilt virus 
               
               
                   
                 Arenaviridae 
                 Arenavirus 
                 Lymphocytic 
               
               
                   
                   
                   
                 choriomeningitis 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Ophiovirus 
                 Citrus psorosis 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Tenuivirus 
                 Rice stripe virus 
               
               
                   
                   
                 Deltavirus 
                 Hepatitis delta 
               
               
                   
                   
                   
                 virus 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 7 
               
             
            
               
                   
               
               
                   
               
               
                 Positive Sense ssRNA Viruses 
               
            
           
           
               
               
               
               
            
               
                   
                   
                   
                 Type Species 
               
               
                 Order 
                 Family 
                 Genus 
                 Example 
               
               
                   
               
               
                   
                 Leviviridae 
                 Levivirus 
                 Enterobacteria phage 
               
               
                   
                   
                   
                 MS2 
               
               
                   
                   
                 Allolevivirus 
                 Enterobacteria phage 
               
               
                   
                   
                   
                 Qβ 
               
               
                   
                 Dicistroviridae 
                 Cripavirus 
                 Cricket paralysis 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Iflavirus (was 
                 Infectious flacherie 
               
               
                   
                   
                 “Infectious 
                 virus 
               
               
                   
                   
                 flacherie-like 
               
               
                   
                   
                 viruses”) 
               
               
                   
                 Picornaviridae 
                 Enterovirus 
                 Poliovirus 
               
               
                   
                   
                 Rhinovirus 
                 Human rhinovirus A 
               
               
                   
                   
                 Hepatovirus 
                 Hepatitis A virus 
               
               
                   
                   
                 Cardiovirus 
                 Encephalomyocarditis 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Aphthovirus 
                 Foot-and-mouth 
               
               
                   
                   
                   
                 disease virus 
               
               
                   
                   
                 Parechovirus 
                 Human parechovirus 
               
               
                   
                 Sequiviridae 
                 Sequivirus 
                 Parsnip yellow fleck 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Waikavirus 
                 Rice tungro spherical 
               
               
                   
                   
                   
                 virus 
               
               
                   
                 Comoviridae 
                 Comovirus 
                 Cowpea mosaic virus 
               
               
                   
                   
                 Fabavirus 
                 Broad bean wilt 
               
               
                   
                   
                   
                 virus 1 
               
               
                   
                   
                 Nepovirus 
                 Tobacco ringspot 
               
               
                   
                   
                   
                 virus 
               
               
                   
                 Potyviridae 
                 Potyvirus 
                 Potato virus Y 
               
               
                   
                   
                 Rymovirus 
                 Ryegrass mosaic 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Bymovirus 
                 Barley yellow mosaic 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Macluravirus 
                 Maclura mosaic virus 
               
               
                   
                   
                 Ipomovirus 
                 Sweet potato mild 
               
               
                   
                   
                   
                 mottle virus 
               
               
                   
                   
                 Tritimovirus 
                 Wheat streak mosaic 
               
               
                   
                   
                   
                 virus 
               
               
                   
                 Caliciviridae 
                 Vesivirus 
                 Swine vesicular 
               
               
                   
                   
                   
                 exanthema virus 
               
               
                   
                   
                 Lagovirus 
                 Rabbit hemorrhagic 
               
               
                   
                   
                   
                 disease virus 
               
               
                   
                   
                 Norovirus (was 
                 Norwalk virus 
               
               
                   
                   
                 “Norwalk-like 
               
               
                   
                   
                 viruses”) 
               
               
                   
                   
                 Sapovirus (was 
                 Sapporo virus 
               
               
                   
                   
                 “Sapporo-like 
               
               
                   
                   
                 viruses”) 
               
               
                   
                 Hepeviridae 
                 Hepevirus (was 
                 Hepatitis E virus 
               
               
                   
                   
                 “Hepatitis E-like 
               
               
                   
                   
                 viruses”) 
               
               
                   
                 Astroviridae 
                 Astrovirus 
                 Human astrovirus 1 
               
               
                   
                 Nodaviridae 
                 Alphanodavirus 
                 Nodamura virus 
               
               
                   
                   
                 Betanodavirus 
                 Striped jack nervous 
               
               
                   
                   
                   
                 necrosis virus 
               
               
                   
                 Tetraviridae 
                 Betatetravirus 
                 Nudaurelia capensis β 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Omegatetravirus 
                 Nudaurelia capensis 
               
               
                   
                   
                   
                 ω virus 
               
               
                   
                 Tombusviridae 
                 Tombusvirus 
                 Tomato bushy stunt 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Carmovirus 
                 Carnation mottle 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Necrovirus 
                 Tobacco necrosis 
               
               
                   
                   
                   
                 virus A 
               
               
                   
                   
                 Dianthovirus 
                 Carnation ringspot 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Machlomovirus 
                 Maize chlorotic 
               
               
                   
                   
                   
                 mottle virus 
               
               
                   
                   
                 Avenavirus 
                 Oat chlorotic stunt 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Aureusvirus 
                 Pothos latent virus 
               
               
                   
                   
                 Panicovirus 
                 Panicum mosaic virus 
               
               
                 Nidovirales 
                 Coronaviridae 
                 Coronavirus 
                 Infectious bronchitis 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Torovirus 
                 Equine torovirus 
               
               
                   
                 Arteriviridae 
                 Arterivirus 
                 Equine arteritis virus 
               
               
                   
                 Roniviridae 
                 Okavirus 
                 Gill-associated virus 
               
               
                   
                 Togaviridae 
                 Alphavirus 
                 Sindbis virus 
               
               
                   
                   
                 Rubivirus 
                 Rubella virus 
               
               
                   
                 Flaviviridae 
                 Flavivirus 
                 Yellow fever virus 
               
               
                   
                   
                 Pestivirus 
                 Bovine viral diarrhea 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Hepacivirus 
                 Hepatitis C virus 
               
               
                   
                 Bromoviridae 
                 Alfamovirus 
                 Alfalfa mosaic virus 
               
               
                   
                   
                 Ilarvirus 
                 Tobacco streak virus 
               
               
                   
                   
                 Bromovirus 
                 Brome mosaic virus 
               
               
                   
                   
                 Cucumovirus 
                 Cucumber mosaic 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Oleavirus 
                 Olive latent virus 2 
               
               
                   
                 Closteroviridae 
                 Closterovirus 
                 Beet yellows virus 
               
               
                   
                   
                 Crinivirus 
                 Lettuce infectious 
               
               
                   
                   
                   
                 yellows virus 
               
               
                   
                   
                 Ampelovirus 
                 Grapevine leafroll- 
               
               
                   
                   
                   
                 associated virus 3 
               
               
                   
                 Barnaviridae 
                 Barnavirus 
                 Mushroom 
               
               
                   
                   
                   
                 bacilliform virus 
               
               
                   
                 Luteoviridae 
                 Luteovirus 
                 Barley yellow dwarf 
               
               
                   
                   
                   
                 virus-PAV 
               
               
                   
                   
                 Polerovirus 
                 Potato leafroll virus 
               
               
                   
                   
                 Enamovirus 
                 Pea enation mosaic 
               
               
                   
                   
                   
                 virus-1 
               
               
                   
                   
                 Tobamovirus 
                 Tobacco mosaic virus 
               
               
                   
                   
                 Tobravirus 
                 Tobacco rattle virus 
               
               
                   
                   
                 Hordeivirus 
                 Barley stripe mosaic 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Furovirus 
                 Soil-borne wheat 
               
               
                   
                   
                   
                 mosaic virus 
               
               
                   
                   
                 Pomovirus 
                 Potato mop-top virus 
               
               
                   
                   
                 Pecluvirus 
                 Peanut clump virus 
               
               
                   
                   
                 Benyvirus 
                 Beet necrotic yellow 
               
               
                   
                   
                   
                 vein virus 
               
               
                   
                   
                 Idaeovirus 
                 Raspberry bushy 
               
               
                   
                   
                   
                 dwarf virus 
               
               
                   
                   
                 Capillovirus 
                 Apple stem grooving 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Trichovirus 
                 Apple chlorotic leaf 
               
               
                   
                   
                   
                 spot virus 
               
               
                   
                   
                 Sobemovirus 
                 Southern bean mosaic 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Umbravirus 
                 Carrot mottle virus 
               
               
                   
                 Tymoviridae 
                 Tymovirus 
                 Turnip yellow mosaic 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Marafivirus 
                 Maize rayado fino 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Maculavirus 
                 Grapevine fleck virus 
               
               
                   
                   
                 Carlavirus 
                 Carnation latent virus 
               
               
                   
                   
                 Potexvirus 
                 Potato virus X 
               
               
                   
                   
                 Allexivirus 
                 Shallot virus X 
               
               
                   
                   
                 Foveavirus 
                 Apple stem pitting 
               
               
                   
                   
                   
                 virus 
               
               
                   
                   
                 Vitivirus 
                 Grap vine virus A 
               
               
                   
                   
                 Ourmiavirus 
                 Ourmia melon virus 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                   
               
               
                 Naked RNA Viruses 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                   
                 Type Species 
               
               
                   
                 Order 
                 Family 
                 Genus 
                 Example 
               
               
                   
                   
               
               
                   
                   
                 Narnaviridae 
                 Narnavirus 
                 Saccharomyces 
               
               
                   
                   
                   
                   
                 cerevisiae 20SRNA 
               
               
                   
                   
                   
                   
                 narnavirus 
               
               
                   
                   
                   
                 Mitovirus 
                 Cryphonectria 
               
               
                   
                   
                   
                   
                 parasitica mitovirus- 
               
               
                   
                   
                   
                   
                 1 NB631 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 9 
               
             
            
               
                   
               
               
                   
               
               
                 Viroids 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                   
                 Type Species 
               
               
                   
                 Order 
                 Family 
                 Genus 
                 Example 
               
               
                   
                   
               
               
                   
                   
                 Pospiviroidae 
                 Pospiviroid 
                 Potato spindle tuber 
               
               
                   
                   
                   
                   
                 viroid 
               
               
                   
                   
                   
                 Hostuviroid 
                 Hop stunt viroid 
               
               
                   
                   
                   
                 Cocadviroid 
                 Coconut cadang- 
               
               
                   
                   
                   
                   
                 cadang viroid 
               
               
                   
                   
                   
                 Apscaviroid 
                 Apple scar skin 
               
               
                   
                   
                   
                   
                 viroid 
               
               
                   
                   
                   
                 Coleviroid 
                 Coleus blumei 
               
               
                   
                   
                   
                   
                 viroid 1 
               
               
                   
                   
                 Avsunviroidae 
                 Avsunviroid 
                 Avocado sunblotch 
               
               
                   
                   
                   
                   
                 viroid 
               
               
                   
                   
                   
                 Pelamoviroid 
                 Peach latent mosaic 
               
               
                   
                   
                   
                   
                 viroid 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 10 
               
             
            
               
                   
               
               
                   
               
               
                 Subviral Agents 
               
            
           
           
               
               
               
               
            
               
                 Agent 
                 Group 
                 Type 
                 Subgroup/Species 
               
               
                   
               
               
                 Satellites 
                 Satellite Viruses 
                 Single-Stranded 
                 Chronic bee- 
               
               
                   
                   
                 RNA Satellite 
                 paralysis satellite 
               
               
                   
                   
                 Viruses 
                 virus 
               
               
                   
                   
                   
                 Tobacco necrosis 
               
               
                   
                   
                   
                 satellite virus 
               
               
                   
                 Satellite Nucleic 
                 Single-Stranded 
                 Tomato leaf curl 
               
               
                   
                 Acids 
                 Satellite DNAs 
                 virus satellite DNA 
               
               
                   
                   
                 Double-Stranded 
                 satellite of 
               
               
                   
                   
                 Satellite RNAs 
                 Saccaromyces 
               
               
                   
                   
                   
                 cerevisiae M virus 
               
               
                   
                   
                 Single-Stranded 
                 Large Satellite 
               
               
                   
                   
                 Satellite RNAs 
                 RNAs 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 11A 
               
             
            
               
                   
               
               
                   
               
               
                 RNA Viruses in Disease 
               
            
           
           
               
               
               
               
            
               
                   
                 Virus 
                   
                   
               
               
                 Family 
                 Subfamily or 
                 Host: 
                 Host: 
               
               
                 (Viridae) 
                 Genus 
                 Humans, Monkeys 
                 Other Animals 
               
               
                   
               
               
                 Picorna 
                 Entero 
                 Enteritis, occasionally 
                 Enteritis 
               
               
                   
                   
                 CNS (polio) 
               
               
                   
                 Cardio 
                 — 
                 Encephalomyocarditis 
               
               
                   
                 Rhino 
                 Common Cold (many 
                 Respiratory 
               
               
                   
                   
                 serotypes) 
               
               
                   
                 Aphtho 
                 — 
                 Foot and Mouth Disease 
               
               
                 Corona 
                 — 
                 Respiratory and enteric 
                 Many different diseases in 
               
               
                   
                   
                   
                 different animals 
               
               
                 Toga 
                 Alpha 
                 Rare encephalitis 
                 Equine, etc. encephalitis 
               
               
                   
                 Flavi 
                 Yellow fever, 
                 Equine, etc. encephalitis 
               
               
                   
                   
                 encephalitis 
               
               
                   
                 Rubi 
                 Skin rash, German 
                 — 
               
               
                   
                   
                 Measles (rubella) 
               
               
                   
                 Pesti 
                 Occasionally congenital 
                 Mucosal disease (cattle) 
               
               
                   
                   
                 diseases 
               
               
                 Retro 
                 Type C 
                 T-cell leukemia 
                 Avian, murine, and other 
               
               
                   
                   
                 (HTLV-1); sarcoma 
                 animal leukemias and 
               
               
                   
                   
                 (monkey) 
                 sarcomas 
               
               
                   
                 Type B 
                 — 
                 Murine mammary tumors 
               
               
                   
                 Type D 
                 Immune deficiency 
                 — 
               
               
                   
                   
                 (monkey) 
               
               
                   
                 Lenti 
                 AIDS, encephalopathy, 
                 Immune deficiency (cats), 
               
               
                   
                   
                 Immune deficiency 
                 maedi visna (sheep), 
               
               
                   
                   
                 (monkey) 
                 encephalopathy, arthritis 
               
               
                   
                   
                   
                 (goats) 
               
               
                 Rhabdo 
                 Vesiculo 
                 — 
                 Stomatitis (cattle, swine) 
               
               
                   
                 Lyssa 
                 Rabies 
                 Rabies 
               
               
                 Filo 
                 — 
                 Hemorrhagic fever 
                 — 
               
               
                   
                   
                 (Marburg, Ebola) 
               
               
                 Arena 
                 — 
                 Hemorrhagic fever 
                 Lymphocytic choriomeningitis 
               
               
                   
                   
                 (Lassa) 
                 (mice) 
               
               
                 Bunya 
                 Bunyamwera 
                 Encephalitis (Calif. 
                 Many diseases 
               
               
                   
                   
                 Enceph.) 
               
               
                 Paramyxo 
                 Paramyxo 
                 Childhood respiratory, 
                 Newcastle disease (birds) 
               
               
                   
                   
                 croup (parainfluenza), 
               
               
                   
                   
                 salivary gland (Mumps) 
               
               
                   
                 Morbilli 
                 Skin rash (measles) 
                 Rinderpest (cattle), distemper 
               
               
                   
                   
                   
                 (dogs) 
               
               
                   
                 Pneumo 
                 Childhood lower 
               
               
                   
                   
                 respiratory, Pneumonia 
               
               
                   
                   
                 (respiratory syncitial) 
               
               
                 Orthomyxo 
                 Type A 
                 Influenza (flu) 
                 Respiratory 
               
               
                   
                 Type B 
                 Influenza 
                 — 
               
               
                 Reo 
                 Orthoreo 
                 — 
                 — 
               
               
                   
                 Orbi 
                 Diarrhea 
                 Diarrhea (blue-tongue of sheep) 
               
               
                   
                 Rota 
                 Children&#39;s diarrhea 
                 Enteric 
               
               
                   
                 Cytoplasmic 
                 — 
                 Lethal insect infection 
               
               
                   
                 polyhedrosis 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 11B 
               
             
            
               
                   
               
               
                   
               
               
                 DNA Viruses in Disease 
               
            
           
           
               
               
               
               
            
               
                 Family 
                 Virus Subfamily 
                 Host: 
                 Host: 
               
               
                 (Viridae) 
                 or Genus 
                 Humans, Monkeys 
                 Other Animals 
               
               
                   
               
               
                 Parvo 
                 — 
                 Aplastic anemia 
                 Enteritis (dogs, cats), 
               
               
                   
                   
                 (humans), Fifth disease 
                 Encephalopathy (rats), 
               
               
                   
                   
                 (B19) 
                 Prenatal infections 
               
               
                 Hepadna 
                 — 
                 Hepatitis 
                 Same (woodchucks, 
               
               
                   
                   
                   
                 squirrels, ducks) 
               
               
                 Papova 
                 Polyoma 
                 Malignant tumors under 
                 Same 
               
               
                   
                   
                 certain specific conditions; 
               
               
                   
                   
                 encephalopathy 
               
               
                   
                 Papilloma 
                 Warts, carcinomas 
                 Warts, at times 
               
               
                   
                   
                   
                 malignant (Shope 
               
               
                   
                   
                   
                 papilloma) 
               
               
                 Adeno 
                 (Many serotypes) 
                 Acute respiratory 
                 Same (occasionally 
               
               
                   
                   
                 diseases, conjunctivitis 
                 oncogenic) 
               
               
                 Herpes 
                 Alphaherpes 
                 Skin rash: chickenpox, 
                 — 
               
               
                   
                   
                 varicella 
               
               
                   
                   
                 Cold sores, shingles 
                 Bovine mammalitis, etc. 
               
               
                   
                   
                 (herpes simplex 1) 
               
               
                   
                   
                 Venereal, congential 
               
               
                   
                   
                 (herpes simplex 2) 
               
               
                   
                 Betaherpes 
                 Congenital 
                 Respiratory and 
               
               
                   
                   
                 malformations 
                 congenital diseases 
               
               
                   
                   
                 (cytomegalo) 
               
               
                   
                 Gammaherpes 
                 Infectious 
                 Marek&#39;s disease 
               
               
                   
                   
                 mononucleosis, etc. 
                 (chickens) 
               
               
                   
                   
                 (Epstein-Barr) 
               
               
                 Baculo 
                 (nuclear 
                 — 
                 Lethal insect infections 
               
               
                   
                 polyhedrosis, 
               
               
                   
                 granulosis) 
               
               
                 Pox 
                 (Many Genera) 
                 Smallpox; Yaba 
                 Pox, myxomatosis 
               
               
                   
                   
                 (monkey) 
               
               
                 Unclassified 
                 — 
                 Non-A, non-B hepatitis, 
                 — 
               
               
                   
                   
                 liver cancer