Abstract:
Methods and compositions for increasing yield in plants, particularly seed plants, are provided. The compositions comprise novel nucleic acid molecules encoding invertase inhibitors, antisense nucleotides corresponding to invertase inhibitors, and variants and fragments thereof. Such compositions find use in methods to modulate invertase activity in plants. The compositions are also useful in methods to modulate kernel development and for protecting plants against the harmful/detrimental effects of stress and adverse environmental conditions. The nucleotide sequences may be provided in constructs for temporal, developmental, and tissue preference.  
     Transformed plants, plant cells, tissues, and seeds are additionally provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of U.S. Provisional No. 60/181,509, filed Feb. 10, 2000. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The invention is drawn to the genetic modification of plants, particularly to the ablation of invertase inhibitor function to maintain female fertility.  
         BACKGROUND OF THE INVENTION  
         [0003]    In cereals, water deficits can disrupt reproductive development and induce large yield reductions. In fact, the shortage of water during pollination increases the frequence of kernel abortion in maize (Westgate &amp; Boyer (1986)  Crop Sci.  26:951). The effects of water deficit are also seen around anthesis which also affects grain number (Schussler &amp; Westgate (1991)  Crop Sci.  31:1196). The losses around anthesis have been variously attributed to abnormal embryo-sac development or decreased silk receptivity depending upon when the water deficit occurs.  
           [0004]    Low water potential inhibits dry matter accumulation and increases the concentration of assimilates in reproductive tissues (Zinselmeier et al. (1995)  Plant Physiol.  107:385). Leaf water potentials decrease as water deficits develop, and photosynthesis is inhibited at the low water potentials causing embryo abortion. It has been demonstrated that by infusing a modified tissue culture medium into the stems and maintaining the supply of carbohydrate in addition to amino acids, basal salts, plant growth regulators, vitamins, and myo-inositol, early reproductive development could be sustained (Boyle et al. (1991)  Crop Sci.  31:1246).  
           [0005]    Under conditions of adequate water, maize ovaries accumulate starch during pollination and early kernel growth. The partitioning into starch reserves depends on assimilate supply as well as demand. At low water potential, starch levels in the reproductive shoot decrease indicating that assimilate supply is not sufficient to meet demand in the reproductive tissues of water-deficient plants.  
           [0006]    Sucrose is the predominate sugar in higher plants. It serves several important functions, including acting as the major carbohydrate transport form, as a storage compound, and as an osmoprotectant. Higher plants metabolize sucrose either by sucrose synthase or by invertases (Greiner et al. (1998)  Plant Physiol.  116:733). Plant invertases are located in the vacuole, the cytoplasm, and the cell wall. These different invertase isoenzymes each have specific functions requiring independent regulation. Several invertase isoforms have been cloned and their expression studied with respect to developmental regulation and tissue or cell-preferred expression (Cheng et al (1996)  Plant Cell  8:971; Weber et al. (1995)  Plant Cell  7:1835).  
           [0007]    Because stress can have deleterious effects on plant growth and yield, methods are needed to increase yield in plants, particularly under stress conditions.  
         SUMMARY OF THE INVENTION  
         [0008]    Methods and compositions for increasing yield in plants, particularly seed plants, are provided. The compositions comprise novel nucleic acid molecules encoding invertase inhibitors, antisense nucleotides corresponding to invertase inhibitors, and variants and fragments thereof. Such compositions find use in methods to modulate invertase activity in plants. The compositions are also useful in methods to modulate kernel development and for protecting plants against the harmful/detrimental effects of stress and adverse environmental conditions. The nucleotide sequences may be provided in constructs for temporal, developmental, and tissue preference.  
           [0009]    Transformed plants, plant cells, tissues, and seeds are additionally provided. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 depicts the effect of recombinant inhibitor on maize invertase activity.  
         [0011]    [0011]FIG. 1A indicates that with increasing quantity of inhibitor, invertase activity decreases.  
         [0012]    [0012]FIG. 1B indicates that sucrose ameliorates the effect of invertase inhibitor on maize invertase.  
         [0013]    [0013]FIG. 2 indicates that gene expression for maize invertase inhibitor is limited to early seed development. RT-PCR was used to detect invertase inhibitor expression in leaf, root, tassel and 4 DAP, 7 DAP, 10 DAP and 15 DAP kernels. Tubulin mRNA was detected as a constitutive control (data not shown).  
         [0014]    [0014]FIG. 3 is a schematic of the transgene construct transferred into maize and arabidopsis plants. The constitutive Ubi (ubiquitin) promoter controls expression of the invertase inhibitor nucleotide sequence.  
         [0015]    [0015]FIG. 4 shows an analysis of overexpression of maize invertase inhibitor in leaf tissue of stable transgenic lines. M1 and M2 are molecular weight markers, while WT present results from an untransformed control. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    Compositions and methods for modulating invertase function in plants are provided. The compositions comprise nucleotide sequences encoding invertase inhibitors, variants and fragments thereof. Nucleotide sequences of the invention also comprise complementary sequences for the invertase inhibitor genes. Particularly, a maize invertase inhibitor is provided.  
         [0017]    Generally, the identification of a maize invertase inhibitor from early kernel tissues suggests that it may modulate kernel development in response to a continuing carbohydrate supply. Both the cell wall invertase and its corresponding invertase inhibitor may be co-expressed in early developing kernels. In the presence of sucrose to support early kernel development, the invertase inhibitor remains inactive. Thus, the invertase acts to supply the kernel with glucose and fructose. In instances where there is an inefficient amount of sucrose, the invertase inhibitor becomes active and inhibits the invertase activity resulting in kernel abortion. Thus, stress and transient decreases in sucrose result in irretrievable losses in yield.  
         [0018]    The present invention provides a means for inactivating the activity of the invertase inhibitor preventing yield losses and promoting kernel development. Any method for inactivating the invertase inhibitor in a plant is encompassed by the invention. For example, using a TUSC-like approach, an insertion may be made into the invertase inhibitor coding sequence to disable the gene. See, Benson et al. (1995)  Plant Cell  7:75-84; Mena et al. (1996)  Science  274:1537-1540; and U.S. Pat. No. 5,962,764; herein incorporated by reference. Likewise, the coding sequence or antisense sequence for the invertase inhibitor coding sequence may be used to co-suppress or antisense the activity of the invertase inhibitor gene.  
         [0019]    Unlike previously characterized invertase inhibitors (e.g. WO 98/04722, WO 00/09719), it has been shown that the yeast invertase gene is sensitive to the invertase inhibitors of the invention (Table 1). The yeast invertase is less sensitive to the invertase inhibitors of the invention than other invertases (FIG. 1, Table 1). Therefore the yeast invertase is an attractive option to supplement invertase activity in a plant. The yeast invertase gene could be used in an expression cassette, particularly with promoters to drive expression during early kernel development. Yeast invertase sequences for use in the invention include, for example, Weber et al. (1998)  Plant J.  16:163; Sonnewald et al. (1991)  Plant J.  1:95-106; von Schaewen et al. (1990)  EMBO J.  10: 3033; Silveira et al. (1996)  Anal Biochem  238:26, Roitsch et al. (1989)  Eur. J. Biochem  181:733; Tussig et al. (1983)  Nucleic Acids Res.  11: 1943-54; the disclosures of which are herein incorporated by reference. The construct may further comprise an apoplastic targeting signal to direct it to the cell wall. This approach would essentially supplement invertase activity in a plant.  
                                           TABLE 1                           Effect of recombinant invertase inhibitor on invertase activity.       Effect of recombinant invertase inhibitor on invertase activity (umol       reducing sugar/mg protein/min; SD in parentheses; n = 3). Yeast       values are expressed in mol reducing sugar; n = 6). +Inh = 75 pMol       recombinant invertase inhibitor, +Suc = 5 mM sucrose.                Invertase Activity            Protein Preparation   −Inh, −Suc   +Inh, −Suc   +Inh, +Suc               Arabidopsis Soluble    2.9 (0.11)    1.6 (0.23)    2.3 (0.04)       Arabidopsis Insoluble    1.8 (0.09)    1.3 (0.10)    1.5 (0.11)       Tomato Soluble   303.8 (8.3)   248.9 (11.9)   317.5 (32.7)       Tomato Insoluble    29.2 (5.1)    12.8 (3.3)    20.9 (0.44)       Yeast    2.9 (0.20)    1.7 (0.19)    1.8 (0.19)                  
 
         [0020]    Compositions of the invention include nucleotide sequences that are involved in invertase inhibitor activity. In particular, the present invention provides for isolated nucleic acid molecules set forth in SEQ ID NO[s]: 1, 4, 7, 10, 13, 16, 19, 22, 25, 28, 31, 34, 37, 40, 43, 46, 49, and 52 comprising nucleotide sequences encoding the amino acid sequences shown in SEQ ID NO[s]: 2, 5, 8, 11, 14, 17, 20, 23, 26, 29, 32, 35, 38, 41, 44, 47, 50, and 53, respectively. The coding sequence of SEQ ID NO[s]: 2, 5, 8, 11, 14, 17, 20, 23, 26, 29, 32, 35, 38, 41, 44, 47, 50, and 53 are provided in SEQ ID NO: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 42, 45, 48, 51, and 54, respectively. Further provided are polypeptides having an amino acid sequence encoded by a nucleic acid molecule described herein, for example those set forth in SEQ ID NO[s]: 1, 4, 7, 10, 13, 16, 19, 22, 25, 28, 31, 34, 37, 40, 43, 46, 49, 52, and fragments and variants thereof.  
         [0021]    It is recognized that with these nucleotide sequences, antisense constructions, complementary to at least a portion of the messenger RNA (mRNA) for the invertase inhibitor sequences can be constructed. Antisense nucleotides are constructed to hybridize with the corresponding mRNA. Modifications of the antisense sequences may be made as long as the sequences hybridize to and interfere with expression of the corresponding mRNA. In this manner, antisense constructions having 70%, preferably 80%, more preferably 85% sequence identity to the corresponding antisensed sequences may be used. Furthermore, portions of the antisense nucleotides may be used to disrupt the expression of the target gene. Generally, sequences of at least 50 nucleotides, 100 nucleotides, 200 nucleotides, or greater may be used.  
         [0022]    The nucleotide sequences of the present invention may also be used in the sense orientation to suppress the expression of endogenous genes in plants. Methods for suppressing gene expression in plants using nucleotide sequences in the sense orientation are known in the art. The methods generally involve transforming plants with a DNA construct comprising a promoter that drives expression in a plant operably linked to at least a portion of a nucleotide sequence that corresponds to the transcript of the endogenous gene. Typically, such a nucleotide sequence has substantial sequence identity to the sequence of the transcript of the endogenous gene, preferably greater than about 65% sequence identity, more preferably greater than about 85% sequence identity, most preferably 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% sequence identity. See, U.S. Pat. Nos. 5,283,184 and 5,034,323; herein incorporated by reference.  
         [0023]    The invention encompasses isolated or substantially purified nucleic acid or protein compositions. An “isolated” or “purified” nucleic acid molecule or protein, or biologically active portion thereof, is substantially or essentially free from components that normally accompany or interact with the nucleic acid molecule or protein as found in its naturally occurring environment. Thus, an isolated or purified nucleic acid molecule or protein is substantially free of other cellular material, or culture medium when produced by recombinant techniques, or substantially free of chemical precursors or other chemicals when chemically synthesized. Preferably, an “isolated” nucleic acid is free of sequences (preferably protein encoding sequences) that naturally flank the nucleic acid (i.e., sequences located at the 5′ and 3′ ends of the nucleic acid) in the genomic DNA of the organism from which the nucleic acid is derived. For example, in various embodiments, the isolated nucleic acid molecule can contain less than about 5 kb, 4 kb, 3 kb, 2 kb, 1 kb, 0.5 kb, or 0.1 kb of nucleotide sequences that naturally flank the nucleic acid molecule in genomic DNA of the cell from which the nucleic acid is derived. A protein that is substantially free of cellular material includes preparations of protein having less than about 30%, 20%, 10%, 5%, (by dry weight) of contaminating protein. When the protein of the invention or biologically active portion thereof is recombinantly produced, preferably culture medium represents less than about 30%, 20%, 10%, or 5% (by dry weight) of chemical precursors or non-protein-of-interest chemicals.  
         [0024]    Fragments and variants of the disclosed nucleotide sequences and proteins encoded thereby are also encompassed by the present invention. By “fragment” is intended a portion of the nucleotide sequence or a portion of the amino acid sequence and hence protein encoded thereby. Fragments of a nucleotide sequence may encode protein fragments that retain the biological activity of the native protein and hence exhibit invertase inhibitor activity. Alternatively, fragments of a nucleotide sequence that are useful as hybridization probes generally do not encode fragment proteins retaining biological activity. Thus, nucleic acid molecules that are fragments of an invertase inhibitor nucleotide sequence comprise at least 15, 20, 50, 75, 100, 325, 350, 375, 400, 425, 450, 500, 550, 600 or up to 609 nucleotides present in the nucleotide sequences disclosed herein (e.g. 665, 981, 779, 633, 844, 775, 686, 709, 1067, 1214, 782, 814, 766, 826, 983, 609, 673, or 665 nucleotides for SEQ ID NO: 1, 4, 7, 10, 13, 16, 19, 22, 25, 28, 31, 34, 37, 40, 43, 46, 49, or 52, respectively). Alternatively, a nucleic acid molecule that is a fragment of an invertase inhibitor-like nucleotide sequence of the present invention comprises a nucleotide sequence consisting of nucleotides 1-100, 100-200, 200-300, 300-400, 400-500, 500-600, or up to the full length of each nucleotide sequence disclosed herein.  
         [0025]    By “variants” is intended substantially similar sequences. For nucleotide sequences, conservative variants include those sequences that, because of the degeneracy of the genetic code, encode the amino acid sequence of the invertase inhibitor polypeptides of the invention. Naturally occurring allelic variants such as these can be identified with the use of well-known molecular biology techniques, as, for example, with polymerase chain reaction (PCR) and hybridization techniques as outlined below. Variant nucleotide sequences also include synthetically derived nucleotide sequences, such as those generated, for example, by using site-directed mutagenesis but which still encode a protein of the invention. Generally, variants of a particular nucleotide sequence of the invention will have at least 65% or 70%, generally at least 75%, 80%, 85%, preferably about 90%, 91%, 92%, 93%, 94%, 95%, or more preferably 96%, 97%, 98% or 99% sequence identity to that particular nucleotide sequence as determined by sequence alignment programs described elsewhere herein using default parameters.  
         [0026]    By “variant” protein is intended a protein derived from the native protein by deletion (so-called truncation) or addition of one or more amino acids to the N-terminal and/or C-terminal end of the native protein; deletion or addition of one or more amino acids at one or more sites in the native protein; or substitution of one or more amino acids at one or more sites in the native protein. Variant proteins encompassed by the present invention are biologically active, that is they continue to possess the desired biological activity of the native protein, that is, invertase inhibitor activity as described herein. Such variants may result from, for example, genetic polymorphism or from human manipulation. Biologically active variants of the invention will have at least 65% or 70%, generally at least 75%, 80%, 85%, preferably 90%, 91%, 92%, 93%, 94%, 95% or more preferably 96%, 97%, 98% or 99% sequence identity to the amino acid sequence for the native protein as determined by sequence alignment programs described elsewhere herein using default parameters. A biologically active variant of a protein of the invention may differ from that protein by as few as 1-15 amino acid residues, as few as 1-10, such as 6-10, as few as 5, as few as 4, 3, 2, or even 1 amino acid residue.  
         [0027]    The proteins of the invention may be altered in various ways including amino acid substitutions, deletions, truncations, and insertions. Methods for such manipulations are generally known in the art. For example, amino acid sequence variants of the proteins can be prepared by mutations in the DNA. Methods for mutagenesis and nucleotide sequence alterations are well known in the art. See, for example, Kunkel (1985)  Proc. Natl. Acad. Sci. USA  82:488-492; Kunkel et al. (1987)  Methods in Enzymol.  154:367-382; U.S. Pat. No. 4,873,192; Walker and Gaastra, eds. (1983)  Techniques in Molecular Biology  (MacMillan Publishing Company, New York) and the references cited therein. Guidance as to appropriate amino acid substitutions that do not affect biological activity of the protein of interest may be found in the model of Dayhoff et al. (1978)  Atlas of Protein Sequence and Structure (Natl. Biomed. Res. Found., Washington, D.C.), herein incorporated by reference. Conservative substitutions, such as exchanging one amino acid with another having similar properties, may be preferred.    
         [0028]    Thus, the genes and nucleotide sequences of the invention include both the naturally occurring sequences as well as mutant forms. Likewise, the proteins of the invention encompass both naturally occurring proteins as well as variations and modified forms thereof. Such variants will continue to possess the desired activity. Obviously, the mutations that will be made in the DNA encoding the variant must not place the sequence out of reading frame and preferably will not create complementary regions that could produce secondary mRNA structure. See, EP Patent Application Publication No. 75,444.  
         [0029]    The deletions, insertions, and substitutions of the protein sequence encompassed herein are not expected to produce radical changes in the characteristics of the protein. However, when it is difficult to predict the exact effect of the substitution, deletion, or insertion in advance of doing so, one skilled in the art will appreciate that the effect will be evaluated by routine screening assays. That is, the activity can be evaluated by the ability to inhibit invertase activity. See, for example, Weil et al. (1994)  Planta  193:438-45, herein incorporated by reference.  
         [0030]    Variant nucleotide sequences and proteins also encompass sequences and proteins derived from a mutagenic and recombinogenic procedure such as DNA shuffling. With such a procedure, one or more different invertase inhibitor coding sequences can be manipulated to create a new invertase inhibitor possessing the desired properties. In this manner, libraries of recombinant polynucleotides are generated from a population of related sequence polynucleotides comprising sequence regions that have substantial sequence identity and can be homologously recombined in vitro or in vivo. For example, using this approach, sequence motifs encoding a domain of interest may be shuffled between the invertase inhibitor gene of the invention and other known invertase inhibitor genes to obtain a new gene coding for a protein with an improved property of interest, such as insensitivity to sucrose deprivation. In addition, all or a portion of the nucleotide sequences of the invention that encode a fragment or variant of an invertase inhibitor polypeptide may be shuffled between other invertase inhibitor sequences of the invention or other known invertase inhibitor sequences. Strategies for such DNA shuffling are known in the art. See, for example, Stemmer (1994)  Proc. Natl. Acad. Sci. USA  91:10747-10751; Stemmer (1994)  Nature  370:389-391; Crameri et al. (1997)  Nature Biotech.  15:436-438; Moore et al. (1997)  J. Mol. Biol.  272:336-347; Zhang et al. (1997)  Proc. Natl. Acad. Sci. USA  94:4504-4509; Crameri et al. (1998)  Nature  391:288-291; and U.S. Pat. Nos. 5,605,793 and 5,837,458.  
         [0031]    The nucleotide sequences of the invention can be used to isolate corresponding sequences from other organisms, particularly other plants, more particularly other monocots. In this manner, methods such as PCR, hybridization, and the like can be used to identify such sequences based on their sequence homology to the sequence[ ] set forth herein. Sequences isolated based on their sequence identity to the entire sequence set forth herein or to fragments thereof are encompassed by the present invention. Such sequences include sequences that are orthologs of the disclosed sequences. By “orthologs” is intended genes derived from a common ancestral gene and which are found in different species as a result of speciation. Genes found in different species are considered orthologs when their nucleotide sequences and/or their encoded protein sequences share substantial identity as defined elsewhere herein. Functions of orthologs are often highly conserved among species.  
         [0032]    In a PCR approach, oligonucleotide primers can be designed for use in PCR reactions to amplify corresponding DNA sequences from cDNA or genomic DNA extracted from any plant of interest. Methods for designing PCR primers and PCR cloning are generally known in the art and are disclosed in Sambrook et al. (1989)  Molecular Cloning: A Laboratory Manual  (2d ed., Cold Spring Harbor Laboratory Press, Plainview, N.Y.). See also Innis et al., eds. (1990)  PCR Protocols: A Guide to Methods and Applications  (Academic Press, New York); Innis and Gelfand, eds. (1995)  PCR Strategies  (Academic Press, New York); and Innis and Gelfand, eds. (1999)  PCR Methods Manual  (Academic Press, New York). Known methods of PCR include, but are not limited to, methods using paired primers, nested primers, single specific primers, degenerate primers, gene-specific primers, vector-specific primers, partially-mismatched primers, and the like.  
         [0033]    In hybridization techniques, all or part of a known nucleotide sequence is used as a probe that selectively hybridizes to other corresponding nucleotide sequences present in a population of cloned genomic DNA fragments or cDNA fragments (i.e., genomic or cDNA libraries) from a chosen organism. The hybridization probes may be genomic DNA fragments, cDNA fragments, RNA fragments, or other oligonucleotides, and may be labeled with a detectable group such as  32 P, or any other detectable marker. Methods for preparation of probes for hybridization and for construction of cDNA and genomic libraries are generally known in the art and are disclosed in Sambrook et al. (1989)  Molecular Cloning: A Laboratory Manual  (2d ed., Cold Spring Harbor Laboratory Press, Plainview, N.Y.).  
         [0034]    To achieve specific hybridization under a variety of conditions, probes include sequences that are unique among invertase inhibitor sequences and are preferably at least about 10 nucleotides in length, and most preferably at least about 20 nucleotides in length. Such probes may be used to amplify corresponding sequences from a chosen plant or organism by PCR. Hybridization techniques include hybridization screening of plated DNA libraries (either plaques or colonies; see, for example, Sambrook et al. (1989)  Molecular Cloning: A Laboratory Manual  (2d ed., Cold Spring Harbor Laboratory Press, Plainview, N.Y.).  
         [0035]    Hybridization of such sequences may be carried out under stringent conditions. By “stringent conditions” or “stringent hybridization conditions” is intended conditions under which a probe will hybridize to its target sequence to a detectably greater degree than to other sequences (e.g., at least 2-fold over background). Stringent conditions are sequence-dependent and will be different in different circumstances. By controlling the stringency of the hybridization and/or washing conditions, target sequences that are 100% complementary to the probe can be identified (homologous probing). Alternatively, stringency conditions can be adjusted to allow some mismatching in sequences so that lower degrees of similarity are detected (heterologous probing). Generally, a probe is less than about 1000 nucleotides in length, preferably less than 500 nucleotides in length.  
         [0036]    Typically, stringent conditions will be those in which the salt concentration is less than about 1.5 M Na ion, typically about 0.01 to 1.0 M Na ion concentration (or other salts) at pH 7.0 to 8.3 and the temperature is at least about 30° C. for short probes (e.g., 10 to 50 nucleotides) and at least about 60° C. for long probes (e.g., greater than 50 nucleotides). Stringent conditions may also be achieved with the addition of destabilizing agents such as formamide. Exemplary low stringency conditions include hybridization with a buffer solution of 30 to 35% formamide, 1 M NaCl, 1% SDS (sodium dodecyl sulphate) at 37° C., and a wash in 1× to 2×SSC (20×SSC =3.0 M NaCl/0.3 M trisodium citrate) at 50 to 55° C. Exemplary moderate stringency conditions include hybridization in 40 to 45% formamide, 1.0 M NaCl, 1% SDS at 37° C., and a wash in 0.5× to 1×SSC at 55 to 60° C. Exemplary high stringency conditions include hybridization in 50% formamide, 1 M NaCl, 1% SDS at 37° C., and a wash in 0.1×SSC at 60 to 65° C. Duration of hybridization is generally less than about 24 hours, usually about 4 to about 12 hours.  
         [0037]    Specificity is typically the function of post-hybridization washes, the critical factors being the ionic strength and temperature of the final wash solution. For DNA-DNA hybrids, the T m  can be approximated from the equation of Meinkoth and Wahl (1984)  Anal. Biochem.  138:267-284: T m =81.5° C.+16.6 (log M)+0.41 (%GC)−0.61 (% form)−500/L; where M is the molarity of monovalent cations, %GC is the percentage of guanosine and cytosine nucleotides in the DNA, % form is the percentage of formamide in the hybridization solution, and L is the length of the hybrid in base pairs. The T m  is the temperature (under defined ionic strength and pH) at which 50% of a complementary target sequence hybridizes to a perfectly matched probe. T m  is reduced by about 1° C. for each 1% of mismatching; thus, T m , hybridization, and/or wash conditions can be adjusted to hybridize to sequences of the desired identity. For example, if sequences with ≧90% identity are sought, the T m  can be decreased 10° C. Generally, stringent conditions are selected to be about 5° C. lower than the thermal melting point (T m ) for the specific sequence and its complement at a defined ionic strength and pH. However, severely stringent conditions can utilize a hybridization and/or wash at 1, 2, 3, or 4° C. lower than the thermal melting point (T m ); moderately stringent conditions can utilize a hybridization and/or wash at 6, 7, 8, 9, or 10° C. lower than the thermal melting point (T m ); low stringency conditions can utilize a hybridization and/or wash at 11, 12, 13, 14, 15, or 20° C. lower than the thermal melting point (T m ). Using the equation, hybridization and wash compositions, and desired T m , those of ordinary skill will understand that variations in the stringency of hybridization and/or wash solutions are inherently described. If the desired degree of mismatching results in a T m  of less than 45° C. (aqueous solution) or 32° C. (formamide solution), it is preferred to increase the SSC concentration so that a higher temperature can be used. An extensive guide to the hybridization of nucleic acids is found in Tijssen (1993)  Laboratory Techniques in Biochemistry and Molecular Biology—Hybridization with Nucleic Acid Probes , Part I, Chapter 2 (Elsevier, N.Y.); and Ausubel et al., eds. (1995)  Current Protocols in Molecular Biology , Chapter 2 (Greene Publishing and Wiley-Interscience, New York). See Sambrook et al. (1989)  Molecular Cloning: A Laboratory Manual  (2d ed., Cold Spring Harbor Laboratory Press, Plainview, N.Y.).  
         [0038]    Thus, isolated sequences that encode for an invertase inhibitor protein and which hybridize under stringent conditions to the sequences disclosed herein, or to fragments thereof, are encompassed by the present invention. Such sequences will be at least about 60%, 65%, or 70% homologous, and even at least about 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more homologous with the disclosed sequence[s]. That is, the sequence identity of sequences may range, sharing at least about 60%, 65%, or 70%, and even at least about 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more sequence identity.  
         [0039]    The following terms are used to describe the sequence relationships between two or more nucleic acids or polynucleotides: (a) “reference sequence”, (b) “comparison window”, (c) “sequence identity”, (d) “percentage of sequence identity”, and (e) “substantial identity”.  
         [0040]    (a) As used herein, “reference sequence” is a defined sequence used as a basis for sequence comparison. A reference sequence may be a subset or the entirety of a specified sequence; for example, as a segment of a full-length cDNA or gene sequence, or the complete cDNA or gene sequence.  
         [0041]    (b) As used herein, “comparison window” makes reference to a contiguous and specified segment of a polynucleotide sequence, wherein the polynucleotide sequence in the comparison window may comprise additions or deletions (i.e., gaps) compared to the reference sequence (which does not comprise additions or deletions) for optimal alignment of the two sequences. Generally, the comparison window is at least 20 contiguous nucleotides in length, and optionally can be 30, 40, 50, 100, or longer. Those of skill in the art understand that to avoid a high similarity to a reference sequence due to inclusion of gaps in the polynucleotide sequence a gap penalty is typically introduced and is subtracted from the number of matches.  
         [0042]    Methods of alignment of sequences for comparison are well known in the art. Thus, the determination of percent sequence identity between any two sequences can be accomplished using a mathematical algorithm. Non-limiting examples of such mathematical algorithms are the algorithm of Myers and Miller (1988)  CABIOS  4:11-17; the local homology algorithm of Smith et al. (1981)  Adv. Appl. Math.  2:482; the homology alignment algorithm of Needleman and Wunsch (1970)  J. Mol. Biol.  48:443-453; the search-for-similarity-method of Pearson and Lipman (1988)  Proc. Natl. Acad. Sci.  85:2444-2448; the algorithm of Karlin and Altschul (1990)  Proc. Natl. Acad. Sci. USA  872264, modified as in Karlin and Altschul (1993)  Proc. Natl. Acad. Sci. USA  90:5873-5877.  
         [0043]    Computer implementations of these mathematical algorithms can be utilized for comparison of sequences to determine sequence identity. Such implementations include, but are not limited to: CLUSTAL in the PC/Gene program (available from Intelligenetics, Mountain View, Calif.); the ALIGN program (Version 2.0) and GAP, BESTFIT, BLAST, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Version 8 (available from Genetics Computer Group (GCG), 575 Science Drive, Madison, Wis., USA). Alignments using these programs can be performed using the default parameters. The CLUSTAL program is well described by Higgins et al. (1988)  Gene  73:237-244 (1988); Higgins et al. (1989)  CABIOS  5:151-153; Corpet et al. (1988)  Nucleic Acids Res.  16:10881-90; Huang et al. (1992)  CABIOS  8:155-65; and Pearson et al. (1994)  Meth. Mol. Biol.  24:307-331. The ALIGN program is based on the algorithm of Myers and Miller (1988) supra. A PAM120 weight residue table, a gap length penalty of 12, and a gap penalty of 4 can be used with the ALIGN program when comparing amino acid sequences. The BLAST programs of Altschul et al (1990)  J. Mol. Biol.  215:403 are based on the algorithm of Karlin and Altschul (1990) supra. BLAST nucleotide searches can be performed with the BLASTN program, score=100, wordlength=12, to obtain nucleotide sequences homologous to a nucleotide sequence encoding a protein of the invention. BLAST protein searches can be performed with the BLASTX program, score=50, wordlength=3, to obtain amino acid sequences homologous to a protein or polypeptide of the invention. To obtain gapped alignments for comparison purposes, Gapped BLAST (in BLAST 2.0) can be utilized as described in Altschul et al. (1997)  Nucleic Acids Res.  25:3389. Alternatively, PSI-BLAST (in BLAST 2.0) can be used to perform an iterated search that detects distant relationships between molecules. See Altschul et al. (1997) supra. When utilizing BLAST, Gapped BLAST, PSI-BLAST, the default parameters of the respective programs (e.g., BLASTN for nucleotide sequences, BLASTX for proteins) can be used. See http://www.ncbi.nlm.nih.gov. Alignment may also be performed manually by inspection.  
         [0044]    Unless otherwise stated, sequence identity/similarity values provided herein refer to the value obtained using GAP Version 10 using the following parameters: % identity using GAP Weight of 50 and Length Weight of 3; % similarity using Gap Weight of 12 and Length Weight of 4, or any equivalent program. By “equivalent program” is intended any sequence comparison program that, for any two sequences in question, generates an alignment having identical nucleotide or amino acid residue matches and an identical percent sequence identity when compared to the corresponding alignment generated by the preferred program.  
         [0045]    GAP uses the algorithm of Needleman and Wunsch (1970)  J. Mol. Biol.  48: 443-453, to find the alignment of two complete sequences that maximizes the number of matches and minimizes the number of gaps. GAP considers all possible alignments and gap positions and creates the alignment with the largest number of matched bases and the fewest gaps. It allows for the provision of a gap creation penalty and a gap extension penalty in units of matched bases. GAP must make a profit of gap creation penalty number of matches for each gap it inserts. If a gap extension penalty greater than zero is chosen, GAP must, in addition, make a profit for each gap inserted of the length of the gap times the gap extension penalty. Default gap creation penalty values and gap extension penalty values in Version 10 of the Wisconsin Genetics Software Package for protein sequences are 8 and 2, respectively. For nucleotide sequences the default gap creation penalty is 50 while the default gap extension penalty is 3. The gap creation and gap extension penalties can be expressed as an integer selected from the group of integers consisting of from 0 to 200. Thus, for example, the gap creation and gap extension penalties can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65 or greater.  
         [0046]    GAP presents one member of the family of best alignments. There may be many members of this family, but no other member has a better quality. GAP displays four figures of merit for alignments: Quality, Ratio, Identity, and Similarity. The Quality is the metric maximized in order to align the sequences. Ratio is the quality divided by the number of bases in the shorter segment. Percent Identity is the percent of the symbols that actually match. Percent Similarity is the percent of the symbols that are similar. Symbols that are across from gaps are ignored. A similarity is scored when the scoring matrix value for a pair of symbols is greater than or equal to 0.50, the similarity threshold. The scoring matrix used in Version 10 of the Wisconsin Genetics Software Package is BLOSUM62 (see Henikoff and Henikoff (1989)  Proc. Natl. Acad. Sci. USA  89:10915).  
         [0047]    (c) As used herein, “sequence identity” or “identity” in the context of two nucleic acid or polypeptide sequences makes reference to the residues in the two sequences that are the same when aligned for maximum correspondence over a specified comparison window. When percentage of sequence identity is used in reference to proteins it is recognized that residue positions which are not identical often differ by conservative amino acid substitutions, where amino acid residues are substituted for other amino acid residues with similar chemical properties (e.g., charge or hydrophobicity) and therefore do not change the functional properties of the molecule. When sequences differ in conservative substitutions, the percent sequence identity may be adjusted upwards to correct for the conservative nature of the substitution. Sequences that differ by such conservative substitutions are said to have “sequence similarity” or “similarity”. Means for making this adjustment are well known to those of skill in the art. Typically this involves scoring a conservative substitution as a partial rather than a full mismatch, thereby increasing the percentage sequence identity. Thus, for example, where an identical amino acid is given a score of 1 and a non-conservative substitution is given a score of zero, a conservative substitution is given a score between zero and 1. The scoring of conservative substitutions is calculated, e.g., as implemented in the program PC/GENE (Intelligenetics, Mountain View, Calif.).  
         [0048]    (d) As used herein, “percentage of sequence identity” means the value determined by comparing two optimally aligned sequences over a comparison window, wherein the portion of the polynucleotide sequence in the comparison window may comprise additions or deletions (i.e., gaps) as compared to the reference sequence (which does not comprise additions or deletions) for optimal alignment of the two sequences. The percentage is calculated by determining the number of positions at which the identical nucleic acid base or amino acid residue occurs in both sequences to yield the number of matched positions, dividing the number of matched positions by the total number of positions in the window of comparison, and multiplying the result by 100 to yield the percentage of sequence identity.  
         [0049]    (e)(i) The term “substantial identity” of polynucleotide sequences means that a polynucleotide comprises a sequence that has at least 70% sequence identity, preferably at least 80%, more preferably at least 90%, and most preferably at least 95%, compared to a reference sequence using one of the alignment programs described using standard parameters. One of skill in the art will recognize that these values can be appropriately adjusted to determine corresponding identity of proteins encoded by two nucleotide sequences by taking into account codon degeneracy, amino acid similarity, reading frame positioning, and the like. Substantial identity of amino acid sequences for these purposes normally means sequence identity of at least 60%, more preferably at least 70%, 80%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more sequence identity.  
         [0050]    Another indication that nucleotide sequences are substantially identical is if two molecules hybridize to each other under stringent conditions. Generally, stringent conditions are selected to be about 5° C. lower than the thermal melting point (T m ) for the specific sequence at a defined ionic strength and pH. However, stringent conditions encompass temperatures in the range of about 1° C. to about 20° C. lower than the T m , depending upon the desired degree of stringency as otherwise qualified herein. Nucleic acids that do not hybridize to each other under stringent conditions are still substantially identical if the polypeptides they encode are substantially identical. This may occur, e.g., when a copy of a nucleic acid is created using the maximum codon degeneracy permitted by the genetic code. One indication that two nucleic acid sequences are substantially identical is when the polypeptide encoded by the first nucleic acid is immunologically cross reactive with the polypeptide encoded by the second nucleic acid.  
         [0051]    (e)(ii) The term “substantial identity” in the context of a peptide indicates that a peptide comprises a sequence with at least 65% or 70% sequence identity to a reference sequence, preferably 80%, more preferably 85%, most preferably at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more sequence identity to the reference sequence over a specified comparison window. Preferably, optimal alignment is conducted using the homology alignment algorithm of Needleman and Wunsch (1970)  J. Mol. Biol.  48:443-453. An indication that two peptide sequences are substantially identical is that one peptide is immunologically reactive with antibodies raised against the second peptide. Thus, a peptide is substantially identical to a second peptide, for example, where the two peptides differ only by a conservative substitution. Peptides that are “substantially similar” share sequences as noted above except that residue positions that are not identical may differ by conservative amino acid changes.  
         [0052]    The invertase inhibitor sequences of the invention, including coding sequences and antisense sequences, may be provided in expression cassettes for expression in the plant of interest. The cassette will include 5′ and 3′ regulatory sequences operably linked to a sequence of the invention. By “operably linked” is intended a functional linkage between a promoter and a second sequence, wherein the promoter sequence initiates and mediates transcription of the DNA sequence corresponding to the second sequence. Generally, operably linked means that the nucleic acid sequences being linked are contiguous and, where necessary to join two protein coding regions, contiguous and in the same reading frame. The cassette may additionally contain at least one additional gene to be cotransformed into the organism. Alternatively, the additional gene(s) can be provided on multiple expression cassettes.  
         [0053]    Such an expression cassette is provided with a plurality of restriction sites for insertion of the sequence of interest to be under the transcriptional regulation of the regulatory regions. The expression cassette may additionally contain selectable marker genes.  
         [0054]    The expression cassette will include in the 5′-3′ direction of transcription, a transcriptional and translational initiation region, an invertase inhibitor sequence of the invention, and a transcriptional and translational termination region functional in plants. The transcriptional initiation region, the promoter, may be native or analogous or foreign or heterologous to the plant host. Additionally, the promoter may be the natural sequence or alternatively a synthetic sequence. By “foreign” is intended that the transcriptional initiation region is not found in the native plant into which the transcriptional initiation region is introduced. As used herein, a chimeric gene comprises a coding sequence operably linked to a transcription initiation region that is heterologous to the coding sequence.  
         [0055]    While it may be preferable to express the sequences using heterologous promoters, the promoter sequences used to regulate expression of the claimed nucleotide sequences may be used. Such constructs would change expression levels of invertase inhibitors in the plant or other host cell of interest. Thus, the phenotype of the plant cell or the host cell (i.e. plant, plant cell, or organism of interest) is altered.  
         [0056]    The termination region may be native with the transcriptional initiation region, may be native with the operably linked DNA sequence of interest, or may be derived from another source. Convenient termination regions are available from the Ti-plasmid of  A. tumefaciens , such as the octopine synthase and nopaline synthase termination regions. See also Guerineau et al. (1991)  Mol. Gen. Genet.  262:141-144; Proudfoot (1991)  Cell  64:671-674; Sanfacon et al. (1991)  Genes Dev.  5:141-149; Mogen et al. (1990)  Plant Cell  2:1261-1272; Munroe et al. (1990)  Gene  91:151-158; Ballas et al. (1989)  Nucleic Acids Res.  17:7891-7903; and Joshi et al. (1987)  Nucleic Acid Res.  15:9627-9639.  
         [0057]    Where appropriate, the gene(s) may be optimized for increased expression in the transformed plant. That is, the genes can be synthesized using plant-preferred codons for improved expression. See, for example, Campbell and Gowri (1990)  Plant Physiol.  92:1-11 for a discussion of host-preferred codon usage. Methods are available in the art for synthesizing plant-preferred genes. See, for example, U.S. Pat. Nos. 5,380,831, and 5,436,391, and Murray et al. (1989)  Nucleic Acids Res.  17:477-498, herein incorporated by reference.  
         [0058]    Additional sequence modifications are known to enhance gene expression in a cellular host. These include elimination of sequences encoding spurious polyadenylation signals, exon-intron splice site signals, transposon-like repeats, and other such well-characterized sequences that may be deleterious to gene expression. The G-C content of the sequence may be adjusted to levels average for a given cellular host, as calculated by reference to known genes expressed in the host cell. When possible, the sequence is modified to avoid predicted hairpin secondary mRNA structures.  
         [0059]    The expression cassettes may additionally contain 5′ leader sequences in the expression cassette construct. Such leader sequences can act to enhance translation. Translation leaders are known in the art and include: picornavirus leaders, for example, EMCV leader (Encephalomyocarditis 5′ noncoding region) (Elroy-Stein et al. (1989)  Proc. Natl. Acad. Sci. USA  86:6126-6130); potyvirus leaders, for example, TEV leader (Tobacco Etch Virus) (Gallie et al. (1995)  Gene  165(2):233-238), MDMV leader (Maize Dwarf Mosaic Virus) ( Virology  154:9-20), and human immunoglobulin heavy-chain binding protein (BiP) (Macejak et al. (1991)  Nature  353:90-94); untranslated leader from the coat protein mRNA of alfalfa mosaic virus (AMV RNA 4) (Jobling et al. (1987)  Nature  325:622-625); tobacco mosaic virus leader (TMV) (Gallie et al. (1989) in  Molecular Biology of RNA,  ed. Cech (Liss, N.Y,), pp. 237-256); and maize chlorotic mottle virus leader (MCMV) (Lommel et al. (1991)  Virology  81:382-385). See also, Della-Cioppa et al. (1987)  Plant Physiol.  84:965-968. Other methods known to enhance translation can also be utilized, for example, introns, and the like.  
         [0060]    In preparing the expression cassette, the various DNA fragments may be manipulated, so as to provide for the DNA sequences in the proper orientation and, as appropriate, in the proper reading frame. Toward this end, adapters or linkers may be employed to join the DNA fragments or other manipulations may be involved to provide for convenient restriction sites, removal of superfluous DNA, removal of restriction sites, or the like. For this purpose, in vitro mutagenesis, primer repair, restriction, annealing, resubstitutions, e.g., transitions and transversions, may be involved.  
         [0061]    A number of promoters can be used in the practice of the invention. The promoters can be selected based on the desired outcome. The nucleic acids can be combined with constitutive, tissue-preferred, or other promoters for expression in plants. Such constitutive promoters include, for example, the core promoter of the Rsyn7 promoter (WO 99/43838 and U.S. Pat. No. 6,072,050); the core CaMV 35S promoter (Odell et al. (1985)  Nature  313:810-812); rice actin (McElroy et al. (1990)  Plant Cell  2:163-171); ubiquitin (Christensen et al. (1989)  Plant Mol. Biol.  12:619-632 and Christensen et al. (1992)  Plant Mol. Biol.  18:675-689); pEMU (Last et al. (1991)  Theor. Appl. Genet.  81:581-588); MAS (Velten et al. (1984)  EMBO J.  3:2723-2730); ALS promoter (U.S. Pat. No. 5,659,026), and the like. Other constitutive promoters include, for example, U.S. Pat. Nos. 5,608,149; 5,608,144; 5,604,121; 5,569,597; 5,466,785; 5,399,680; 5,268,463; and 5,608,142.  
         [0062]    “Seed-preferred” promoters include both “seed-specific” promoters (those promoters active during seed development such as promoters of seed storage proteins) as well as “seed-germinating” promoters (those promoters active during seed germination). See Thompson et al. (1989)  BioEssays  10:108, herein incorporated by reference. Such seed-preferred promoters include, but are not limited to, Cim1 (cytokinin-induced message); cZ19B1 (maize 19 kDa zein); milps (myo-inositol-1-phosphate synthase); and celA (cellulose synthase). Gama-zein is one example of endosperm-preferred promoter. Glob-1 is one example of embryo-preferred promoter. For dicots, seed-preferred promoters include, but are not limited to, bean β-phaseolin, napin, β-conglycinin, soybean lectin, cruciferin, and the like. For monocots, seed-preferred promoters include, but are not limited to, maize 15 kDa zein, 22 kDa zein, 27 kDa zein, g-zein, waxy, shrunken 1, shrunken 2, globulin 1, etc.  
         [0063]    Transformation protocols as well as protocols for introducing nucleotide sequences into plants may vary depending on the type of plant or plant cell, i.e., monocot or dicot, targeted for transformation. Suitable methods of introducing nucleotide sequences into plant cells and subsequent insertion into the plant genome include microinjection (Crossway et al. (1986)  Biotechniques  4:320-334), electroporation (Riggs et al. (1986)  Proc. Natl. Acad. Sci. USA  83:5602-5606, Agrobacterium-mediated transformation (Townsend et al., U.S. Pat. No. 5,563,055; Zhao et al., U.S. Pat. No. 5,981,840), direct gene transfer (Paszkowski et al. (1984)  EMBO J.  3:2717-2722), and ballistic particle acceleration (see, for example, Sanford et al., U.S. Pat. No. 4,945,050; Tomes et al., U.S. Pat. No. 5,879,918; Tomes et al., U.S. Pat. No. 5,886,244; Bidney et al., U.S. Pat. No. 5,932,782; Tomes et al. (1995) “Direct DNA Transfer into Intact Plant Cells via Microprojectile Bombardment,” in  Plant Cell, Tissue, and Organ Culture: Fundamental Methods , ed. Gamborg and Phillips (Springer-Verlag, Berlin); and McCabe et al. (1988)  Biotechnology  6:923-926). Also see Weissinger et al. (1988)  Ann. Rev. Genet.  22:421-477; Sanford et al. (1987)  Particulate Science and Technology  5:27-37 (onion); Christou et al. (1988)  Plant Physiol.  87:671-674 (soybean); McCabe et al. (1988)  Bio/Technology  6:923-926 (soybean); Finer and McMullen (1991)  In Vitro Cell Dev. Biol.  27P: 175-182 (soybean); Singh et al. (1998)  Theor. Appl. Genet.  96:319-324 (soybean); Datta et al. (1990)  Biotechnology  8:736-740 (rice); Klein et al. (1988)  Proc. Natl. Acad. Sci. USA  85:4305-4309 (maize); Klein et al. (1988)  Biotechnology  6:559-563 (maize); Tomes, U.S. Pat. No. 5,240,855; Buising et al., U.S. Pat. Nos. 5,322,783 and 5,324,646; Tomes et al. (1995) “Direct DNA Transfer into Intact Plant Cells via Microprojectile Bombardment,” in  Plant Cell, Tissue, and Organ Culture: Fundamental Methods , ed. Gamborg (Springer-Verlag, Berlin) (maize); Klein et al. (1988)  Plant Physiol.  91:440-444 (maize); Fromm et al. (1990)  Biotechnology  8:833-839 (maize); Hooykaas-Van Slogteren et al. (1984)  Nature  (London) 311:763-764; Bowen et al., U.S. Pat. No. 5,736,369 (cereals); Bytebier et al. (1987)  Proc. Natl. Acad. Sci. USA  84:5345-5349 (Liliaceae); De Wet et al. (1985) in  The Experimental Manipulation of Ovule Tissues , ed. Chapman et al. (Longman, N.Y.), pp. 197-209 (pollen); Kaeppler et al. (1990)  Plant Cell Reports  9:415-418 and Kaeppler et al. (1992)  Theor. Appl. Genet.  84:560-566 (whisker-mediated transformation); D&#39;Halluin et al. (1992)  Plant Cell  4:1495-1505 (electroporation); Li et al. (1993)  Plant Cell Reports  12:250-255 and Christou and Ford (1995)  Annals of Botany  75:407-413 (rice); Osjoda et al. (1996)  Nature Biotechnology  14:745-750 (maize via  Agrobacterium tumefaciens ); all of which are herein incorporated by reference.  
         [0064]    The methods of the invention involve introducing a nucleotide construct into a plant. By “introducing” is intended presenting to the plant the nucleotide construct in such a manner that the construct gains access to the interior of a cell of the plant. The methods of the invention do not depend on a particular method for introducing a nucleotide construct to a plant, only that the nucleotide construct gains access to the interior of at least one cell of the plant. Methods for introducing nucleotide constructs into plants are known in the art including, but not limited to, stable transformation methods, transient transformation methods, and virus-mediated methods.  
         [0065]    By “stable transformation” is intended that the nucleotide construct introduced into a plant integrates into the genome of the plant and is capable of being inherited by progeny thereof. By “transient transformation” is intended that a nucleotide construct introduced into a plant does not integrate into the genome of the plant.  
         [0066]    The nucleotide constructs of the invention may be introduced into plants by contacting plants with a virus or viral nucleic acids. Generally, such methods involve incorporating a nucleotide construct of the invention within a viral DNA or RNA molecule. It is recognized that the invertase inhibitor of the invention may be initially synthesized as part of a viral polyprotein, which later may be processed by proteolysis in vivo or in vitro to produce the desired recombinant protein. Further, it is recognized that promoters of the invention also encompass promoters utilized for transcription by viral RNA polymerases. Methods for introducing nucleotide constructs into plants and expressing a protein encoded therein, involving viral DNA or RNA molecules, are known in the art. See, for example, U.S. Pat. Nos. 5,889,191, 5,889,190, 5,866,785, 5,589,367 and 5,316,931; herein incorporated by reference.  
         [0067]    The cells that have been transformed may be grown into plants in accordance with conventional ways. See, for example, McCormick et al. (1986)  Plant Cell Reports  5:81-84. These plants may then be grown, and either pollinated with the same transformed strain or different strains, and the resulting hybrid having constitutive expression of the desired phenotypic characteristic identified. Two or more generations may be grown to ensure that expression of the desired phenotypic characteristic is stably maintained and inherited and then seeds harvested to ensure expression of the desired phenotypic characteristic has been achieved.  
         [0068]    Plants of particular interest include grain plants that provide seeds of interest, oil-seed plants, and leguminous plants. Seeds of interest include grain seeds, such as corn, wheat, barley, rice, sorghum, rye, etc. Oil-seed plants include cotton, soybean, safflower, sunflower, Brassica, maize, alfalfa, palm, coconut, etc. Leguminous plants include beans and peas. Beans include guar, locust bean, fenugreek, soybean, garden beans, cowpea, mungbean, lima bean, fava bean, lentils, chickpea, etc.  
         [0069]    The present invention may be used for transformation of any plant species, including, but not limited to, monocots and dicots. Examples of plants of interest include, but are not limited to, corn ( Zea mays ), Brassica sp. (e.g.,  B. napus, B. rapa, B. juncea ), particularly those Brassica species useful as sources of seed oil, alfalfa ( Medicago sativa ), rice ( Oryza sativa ), rye ( Secale cereale ), sorghum ( Sorghum bicolor, Sorghum vulgare ), millet (e.g., pearl millet ( Pennisetum glaucum ), proso millet ( Panicum miliaceum ), foxtail millet ( Setaria italica ), finger millet ( Eleusine coracana )), sunflower ( Helianthus annuus ), safflower ( Carthamus tinctorius ), wheat ( Triticum aestivum ), soybean ( Glycine max ), tobacco ( Nicotiana tabacum ), potato ( Solanum tuberosum ), peanuts ( Arachis hypogaea ), cotton ( Gossypium barbadense, Gossypium hirsutum ), sweet potato ( Ipomoea batatus ), cassava ( Manihot esculenta ), coffee (Coffea spp.), coconut ( Cocos nucifera ), pineapple ( Ananas comosus ), citrus trees (Citrus spp.), cocoa ( Theobroma cacao ), tea ( Camellia sinensis ), banana (Musa spp.), avocado ( Persea americana ), fig ( Ficus casica ), guava ( Psidium guajava ), mango ( Mangifera indica ), olive ( Olea europaea ), papaya ( Carica papaya ), cashew ( Anacardium occidentale ), macadamia ( Macadamia integrifolia ), almond ( Prunus amygdalus ), sugar beets ( Beta vulgaris ), sugarcane (Saccharum spp.), oats, barley, vegetables, ornamentals, and conifers.  
         [0070]    Vegetables include tomatoes ( Lycopersicon esculentum ), lettuce (e.g.,  Lactuca sativa ), green beans ( Phaseolus vulgaris ), lima beans ( Phaseolus limensis ), peas (Lathyrus spp.), and members of the genus Cucumis such as cucumber ( C. sativus ), cantaloupe ( C. cantalupensis ), and musk melon ( C. melo ). Ornamentals include azalea (Rhododendron spp.), hydrangea ( Macrophylla hydrangea ), hibiscus ( Hibiscus rosasanensis ), roses (Rosa spp.), tulips (Tulipa spp.), daffodils (Narcissus spp.), petunias ( Petunia hybrida ), carnation ( Dianthus caryophyllus ), poinsettia ( Euphorbia pulcherrima ), and chrysanthemum. Conifers that may be employed in practicing the present invention include, for example, pines such as loblolly pine ( Pinus taeda ), slash pine ( Pinus elliotii ), ponderosa pine ( Pinus ponderosa ), lodgepole pine ( Pinus contorta ), and Monterey pine ( Pinus radiata ); Douglas-fir ( Pseudotsuga menziesii ); Western hemlock ( Tsuga canadensis ); Sitka spruce ( Picea glauca ); redwood ( Sequoia sempervirens ); true firs such as silver fir ( Abies amabilis ) and balsam fir ( Abies balsamea ); and cedars such as Western red cedar ( Thuja plicata ) and Alaska yellow-cedar ( Chamaecyparis nootkatensis ). Preferably, plants of the present invention are crop plants (for example, corn, alfalfa, sunflower, Brassica, soybean, cotton, safflower, peanut, sorghum, wheat, millet, tobacco, etc.), more preferably corn and soybean plants, yet more preferably corn plants.  
         [0071]    The following examples are offered by way of illustration and not by way of limitation.  
       EXPERIMENTAL  
     EXAMPLE 1  
     Transformation and Regeneration of Transgenic Plants  
       [0072]    Immature maize embryos from greenhouse donor plants are bombarded with a plasmid containing the antisense sequence corresponding to SEQ ID NO: 1 operably linked to an Ubi promoter plus a plasmid containing the selectable marker gene PAT (Wohlleben et al. (1988)  Gene  70:25-37) that confers resistance to the herbicide Bialaphos. Transformation is performed as follows. Media recipes follow below.  
         [0073]    Preparation of Target Tissue  
         [0074]    The ears are surface sterilized in 30% Chlorox bleach plus 0.5% Micro detergent for 20 minutes, and rinsed two times with sterile water. The immature embryos are excised and placed embryo axis side down (scutellum side up), 25 embryos per plate, on 560Y medium for 4 hours and then aligned within the 2.5-cm target zone in preparation for bombardment.  
         [0075]    Preparation of DNA  
         [0076]    A plasmid vector comprising the antisense sequence corresponding to SEQ ID NO: 1 operably linked to a Rsgn7 promoter is made. This plasmid DNA plus plasmid DNA containing a PAT selectable marker is precipitated onto 1.1 μm (average diameter) tungsten pellets using a CaCl 2  precipitation procedure as follows:  
         [0077]    100 μl prepared tungsten particles in water  
         [0078]    10 μl (1 μg) DNA in TrisEDTA buffer (1 μg total)  
         [0079]    100 μl 2.5 M CaCl 2    
         [0080]    10 μl 0.1 M spermidine  
         [0081]    Each reagent is added sequentially to the tungsten particle suspension, while maintained on the multitube vortexer. The final mixture is sonicated briefly and allowed to incubate under constant vortexing for 10 minutes. After the precipitation period, the tubes are centrifuged briefly, liquid removed, washed with 500 ml 100% ethanol, and centrifuged for 30 seconds. Again the liquid is removed, and 105 μl 100% ethanol is added to the final tungsten particle pellet. For particle gun bombardment, the tungsten/DNA particles are briefly sonicated and 10 μl spotted onto the center of each macrocarrier and allowed to dry about 2 minutes before bombardment.  
         [0082]    Particle Gun Treatment  
         [0083]    The sample plates are bombarded at level #4 in particle gun #HE34-1 or #HE34-2. All samples receive a single shot at 650 PSI, with a total of ten aliquots taken from each tube of prepared particles/DNA.  
         [0084]    Subsequent Treatment  
         [0085]    Following bombardment, the embryos are kept on 560Y medium for 2 days, then transferred to 560R selection medium containing 3 mg/liter Bialaphos, and subcultured every 2 weeks. After approximately 10 weeks of selection, selection-resistant callus clones are transferred to 288J medium to initiate plant regeneration. Following somatic embryo maturation (2-4 weeks), well-developed somatic embryos are transferred to medium for germination and transferred to the lighted culture room. Approximately 7-10 days later, developing plantlets are transferred to 272V hormone-free medium in tubes for 7-10 days until plantlets are well established. Plants are then transferred to inserts in flats (equivalent to 2.5″ pot) containing potting soil and grown for 1 week in a growth chamber, subsequently grown an additional 1-2 weeks in the greenhouse, then transferred to classic 600 pots (1.6 gallon) and grown to maturity. Plants are monitored and scored.  
         [0086]    Bombardment and Culture Media  
         [0087]    Bombardment medium (560Y) comprises 4.0 g/l N6 basal salts (SIGMA C-1416), 1.0 ml/l Eriksson&#39;s Vitamin Mix (1000X SIGMA-1511), 0.5 mg/l thiamine HCl, 120.0 g/l sucrose, 1.0 mg/l 2,4-D, and 2.88 g/l L-proline (brought to volume with D-I H 2 O following adjustment to pH 5.8 with KOH); 2.0 g/l Gelrite (added after bringing to volume with D-I H 2 O); and 8.5 mg/l silver nitrate (added after sterilizing the medium and cooling to room temperature). Selection medium (560R) comprises 4.0 g/l N6 basal salts (SIGMA C-1416), 1.0 ml/l Eriksson&#39;s Vitamin Mix (1000X SIGMA-1511), 0.5 mg/l thiamine HCl, 30.0 g/l sucrose, and 2.0 mg/l 2,4-D (brought to volume with D-I H 2 O following adjustment to pH 5.8 with KOH); 3.0 g/l Gelrite (added after bringing to volume with D-I H 2 O); and 0.85 mg/l silver nitrate and 3.0 mg/l bialaphos(both added after sterilizing the medium and cooling to room temperature).  
         [0088]    Plant regeneration medium (288J) comprises 4.3 g/l MS salts (GIBCO 11117-074), 5.0 ml/l MS vitamins stock solution (0.100 g nicotinic acid, 0.02 g/l thiamine HCL, 0.10 g/l pyridoxine HCL, and 0.40 g/l glycine brought to volume with polished D-I H 2 O) (Murashige and Skoog (1962)  Physiol. Plant.  15:473), 100 mg/l myo-inositol, 0.5 mg/l zeatin, 60 g/l sucrose, and 1.0 ml/l of 0.1 mM abscisic acid (brought to volume with polished D-I H 2 O after adjusting to pH 5.6); 3.0 g/l Gelrite (added after bringing to volume with D-I H 2 O); and 1.0 mg/l indoleacetic acid and 3.0 mg/l bialaphos (added after sterilizing the medium and cooling to 60° C.). Hormone-free medium (272V) comprises 4.3 g/l MS salts (GIBCO 11117-074), 5.0 ml/l MS vitamins stock solution (0.100 g/l nicotinic acid, 0.02 g/l thiamine HCL, 0.10 g/l pyridoxine HCL, and 0.40 g/l glycine brought to volume with polished D-I H 2 O), 0.1 g/l myo-inositol, and 40.0 g/l sucrose (brought to volume with polished D-I H 2 O after adjusting pH to 5.6); and 6 g/l bacto-agar (added after bringing to volume with polished D-I H 2 O), sterilized and cooled to 60° C.  
       EXAMPLE 2  
     Agrobacterium-mediated Transformation  
       [0089]    For Agrobacterium-mediated transformation of maize with a nucleotide sequence of the invention, preferably the method of Zhao is employed (PCT patent publication WO98/32326), the contents of which are hereby incorporated by reference. Briefly, immature embryos are isolated from maize and the embryos contacted with a suspension of Agrobacterium, where the bacteria are capable of transferring the sequences of interest to at least one cell of at least one of the immature embryos (step 1: the infection step). In this step the immature embryos are preferably immersed in an Agrobacterium suspension for the initiation of inoculation. The embryos are co-cultured for a time with the Agrobacterium (step 2: the co-cultivation step). Preferably the immature embryos are cultured on solid medium following the infection step. Following this co-cultivation period an optional “resting” step is contemplated. In this resting step, the embryos are incubated in the presence of at least one antibiotic known to inhibit the growth of Agrobacterium without the addition of a selective agent for plant transformants (step 3: resting step). Preferably the immature embryos are cultured on solid medium with antibiotic, but without a selecting agent, for elimination of Agrobacterium and for a resting phase for the infected cells. Next, inoculated embryos are cultured on medium containing a selective agent and growing transformed callus is recovered (step 4: the selection step). Preferably, the immature embryos are cultured on solid medium with a selective agent resulting in the selective growth of transformed cells. The callus is then regenerated into plants (step 5: the regeneration step), and preferably calli grown on selective medium are cultured on solid medium to regenerate the plants.  
       EXAMPLE 3  
     Soybean Embryo Transformation  
       [0090]    Soybean embryos are bombarded with a plasmid containing the invertase inhibitor gene operably linked to a promoter as follows. To induce somatic embryos, cotyledons, 3-5 mm in length dissected from surface-sterilized, immature seeds of the soybean cultivar A2872, are cultured in the light or dark at 26° C. on an appropriate agar medium for six to ten weeks. Somatic embryos producing secondary embryos are then excised and placed into a suitable liquid medium. After repeated selection for clusters of somatic embryos that multiplied as early, globular-staged embryos, the suspensions are maintained as described below.  
         [0091]    Soybean embryogenic suspension cultures can maintained in 35 ml liquid media on a rotary shaker, 150 rpm, at 26° C. with florescent lights on a 16:8 hour day/night schedule. Cultures are subcultured every two weeks by inoculating approximately 35 mg of tissue into 35 ml of liquid medium.  
         [0092]    Soybean embryogenic suspension cultures may then be transformed by the method of particle gun bombardment (Klein et al. (1987)  Nature  (London) 327:70-73, U.S. Pat. No. 4,945,050). A Du Pont Biolistic PDS1000/HE instrument (helium retrofit) can be used for these transformations.  
         [0093]    A selectable marker gene that can be used to facilitate soybean transformation is a transgene composed of the 35S promoter from Cauliflower Mosaic Virus (Odell et al. (1985)  Nature  313:810-812), the hygromycin phosphotransferase gene from plasmid pJR225 (from  E. coli ; Gritz et al. (1983)  Gene  25:179-188), and the 3′ region of the nopaline synthase gene from the T-DNA of the Ti plasmid of  Agrobacterium tumefaciens . The expression cassette comprising the invertase inhibitor gene operably linked to a preferred promoter can be isolated as a restriction fragment. This fragment can then be inserted into a unique restriction site of the vector carrying the marker gene.  
         [0094]    To 50 μl of a 60 mg/ml 1 μm gold particle suspension is added (in order): 5 μl DNA (1 μg/μl), 20 μl spermidine (0.1 M), and 50 μl CaCl 2  (2.5 M). The particle preparation is then agitated for three minutes, spun in a microfuge for 10 seconds and the supernatant removed. The DNA-coated particles are then washed once in 400 μl 70% ethanol and resuspended in 40 μl of anhydrous ethanol. The DNA/particle suspension can be sonicated three times for one second each. Five microliters of the DNA-coated gold particles are then loaded on each macro carrier disk.  
         [0095]    Approximately 300-400 mg of a two-week-old suspension culture is placed in an empty 60×15 mm petri dish and the residual liquid removed from the tissue with a pipette. For each transformation experiment, approximately 5-10 plates of tissue are normally bombarded. Membrane rupture pressure is set at 1100 psi, and the chamber is evacuated to a vacuum of 28 inches mercury. The tissue is placed approximately 3.5 inches away from the retaining screen and bombarded three times. Following bombardment, the tissue can be divided in half and placed back into liquid and cultured as described above.  
         [0096]    Five to seven days post bombardment, the liquid media may be exchanged with fresh media, and eleven to twelve days post-bombardment with fresh media containing 50 mg/ml hygromycin. This selective media can be refreshed weekly. Seven to eight weeks post-bombardment, green, transformed tissue may be observed growing from untransformed, necrotic embryogenic clusters. Isolated green tissue is removed and inoculated into individual flasks to generate new, clonally propagated, transformed embryogenic suspension cultures. Each new line may be treated as an independent transformation event. These suspensions can then be subcultured and maintained as clusters of immature embryos or regenerated into whole plants by maturation and germination of individual somatic embryos.  
         [0097]    All publications and patent applications mentioned in the specification are indicative of the level of those skilled in the art to which this invention pertains. All publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.  
         [0098]    Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be obvious that certain changes and modifications may be practiced within the scope of the appended claims.