bluuebunny/crossref_metadata_2025 huggingface dataset:
The genetics of 5S rRNA encoding multigene families in barley
Authors: Kanazin Vladimir , Ananiev Evgeny , Blake Tom
Published: May 2008

Two loci containing genes encoding 5S rRNA were mapped on the second and third chromosomes of barley. The two gene clusters located on different chromosomes differed in the length of the nontranscribed spacer separating the 5S rRNA genes. All nontranscribed spacers contained a variable number of trinucleotide tandem repeats. The distribution of 5S genes between these two clusters and their copy number varied widely between cultivars and doubled haploids derived from a cross between two barley cultivars. However, this variation had no obvious effect on plant phenotype.Key words: 5S rRNA genes, multigene families, nontranscribed spacers, trinucleotide tandem repeats, barley, phenotype.
Random amplified polymorphic DNA analysis in Hordeum species
Authors: González Juan Manuel , Ferrer Esther
Published: May 2008

Random amplified polymorphic DNA analysis was performed by applying a set of 13 arbitrary 10-mer primers to 19 Hordeum species and subspecies. High levels of variation in fragment pattern were observed both within and among species with most of the primers used. Genetic similarities between accessions and species were calculated from the fragment patterns. The resulting phenograms confirmed previous relationships among the Hordeum species.Key words: random amplified polymorphic DNA, polymerase chain reaction, polymorphism, Hordeum.
Prolamin variation and evolution in Triticeae as recognized by monoclonal antibodies
Authors: Pelger Susanne
Published: May 2008

The isopropanol-soluble seed storage proteins, prolamins, were studied in 18 different genera of the tribe Triticeae by gel electrophoresis, Coomassie staining, and immunoblot assays. The monoclonal antibodies were originally raised against cultivated barley (Hordeum vulgare L.) hordein, and their reactions had been tested earlier on wild Hordeum species. The study showed that all the investigated Triticeae species produce prolamins and that structural similarities can be found throughout the tribe. The presence of the same antigenic sites in all the species indicates that the polypeptides contain well-conserved regions. They also indicate that the prolamins of the Triticeae species have a common evolutionary origin. In all the investigated species an antigenic site that is common to the B- and C-hordeins of barley was detected. Some of the reacting polypeptides also contained a site that is only present in the B-hordeins. The B-hordein specific site was found in all genera except Agropyron, Hordelymus, and Secale. This shows that although there are similarities between individual polypeptides, the composition of the various prolamin groups may vary between different genera. In the polyploid Elymus species different banding patterns were observed depending on what basic genomes were represented. The results suggest a direct correlation between the presence of a fast migrating polypeptide containing the B-hordein specific site and the presence of the H genome.Key words: Triticeae, prolamin, monoclonal antibodies, evolution, multigene family.
Ribosomal DNA variations in wild and cultivated rubber tree (Hevea brasiliensis)
Authors: Besse Pascale , Seguin Marc , Lebrun Patricia , Lanaud Claire
Published: May 2008

Ribosomal DNA variations were surveyed to assess the genetic variability among Hevea brasiliensis genetic resources. One hundred and sixty-eight individuals, including 73 cultivated Wickham clones and 95 wild clones from a prospection, were analyzed. Restriction mapping of rDNA units showed that RFLP variations are the result of both length and site (EcoRI) variations in the intergenic spacer (IGS). These variations can be revealed between as well as within individuals. A total of 12 spacer length variants is scored in the whole population, as well as two different ribosomal units (refered as type I and type II), defined by the presence or absence of an EcoRI site. Particular associations between spacer length variants and unit types can be revealed, leading to complex RFLP patterns. Cultivated clones appear to be less variable than prospections but show, however, a relatively high level of variability despite their narrow genetic base. Furthermore, IGS variations allowed a structuring within wild clones to be drawn, based mainly on their geographical origin. Some interesting discrepancies with previous work on isozyme variations are discussed and show the interest of surveying different genetic markers for diversity studies.Key words: Hevea brasiliensis, RFLP, rDNA, genetic diversity.
Tissue-specific nuclear repatterning in plant cells
Authors: Ceccarelli M. , Cionini P.G.
Published: May 2008

Tissue-specific nuclear repatternings, consisting of changes in the number and size of the chromocenters, were observed by analyzing, in Feulgen squashes and sections, different tissues of several plant species, particularly of Ionopsidium savianum. Nuclear repatternings occur mainly near the base of the meristems. They are due to associations of chromosomes at their heterochromatic regions. This was confirmed by the results of cytophotometric measurements, showing the same contents of both Feulgen/DNA and heterochromatin in nuclei with a different number of chromocenters. These data also showed that chromosome association does not occur in endoreduplicating or endoreduplicated cells. Autoradiographic results after [3H]thymidine treatments indicated that DNA synthesis does not occur in nuclei with extensive chromosome association. A highly significant, positive correlation was found between the number of chromocenters in each nucleus and the amount of RNA synthesis as indicated by [3H]uridine incorporation. It is suggested that chromosome association plays some role in the regulation of the functional activity of the nucleus and in tissue differentiation.Key words: functional regulation, heterochromatin, nuclear repatterning, plant cell nucleus, tissue differentiation.
The rat adenine phosphoribosyltransferase sequence shows evolutionary rate variation among exons in rodents
Authors: Fieldhouse Dan , Golding G. Brian
Published: May 2008

The complete genomic sequence of the rat APRT gene is described and compared with published mammalian sequences. The rat APRT gene organization is typical of other rodent APRTs with five exons, one large intron of 993 bp, and three smaller introns averaging 145 bp. Because complete sequences for mouse and Chinese hamster APRT are also known, it is possible to compare the evolutionary rates of change in the exons with those of the introns. The latter provide one possible estimate of underlying rates of change. It is shown that the APRT exons have differential rates of evolution in rodents and have had a recent and rapid burst of substitutions within the mouse lineage. Rates of change in the exons do not appear to be strongly correlated with the rates of change in the introns.Key words: APRT, purine salvage enzymes, rates of evolution, rodent.
The use of deficiencies to determine essential gene content in the let-56–unc-22 region of Caenorhabditis elegans
Authors: Schein Jacquie E. , Marra Marco A. , Benian Guy M. , Fields Chris , Baillie David L.
Published: May 2008

We have investigated the possibility of using the polymerase chain reaction to detect deletions of coding elements in the unc-22–let-56 interval on chromosome IV in the nematode Caenorhabditis elegans. Our analysis of approximately 13 kb of genomic sequence immediately to the left of the unc-22 gene resulted in the identification of four possible genes. Partial cDNAs have been identified for three of them. To determine whether any of these coding elements are essential for development, we required a method for the induction and selection of mutations in these elements. Our approach was to identify a set of formaldehyde and gamma radiation induced unc-22 mutations that mapped to the unc-22–let-56 region, and then employ polymerase chain reaction methodology to identify deficiencies that affected one or more of the four identified coding elements. Two small deficiencies were identified in this manner. Characterization of these deficiencies shows that there are no coding elements between unc-22 and let-56 (the nearest mutationally identified gene to the left of unc-22), which are required in development under laboratory conditions. We conclude that the polymerase chain reaction is a practical tool for the detection of deletions of coding elements identified in this region, and that characterization of such deficiencies provides a method for assessing whether or not these elements are required for development.Key words: Caenorhabditis elegans, deficiencies, coding elements, unc-22.
Biosystematic study of hexaploids Elymus tschimganicus and E. glaucissimus. II. Interspecific hybridization and genomic relationship
Authors: Lu Bao-Rong , Jensen Kevin B. , Salomon Björn
Published: May 2008

To investigate genomic relationships of Elymus tschimganicus (Drobov) Tzvelev (2n = 6x = 42, S1S2Y genomes) and E. glaucissimus (M. Pop.) Tzvelev (2n = 6x = 42, S1S2Y genomes), interspecific hybridizations of the two target species were carried out with 27 other Elymus species containing the SH, SY, SYH, SYP, SYW, and SH1H2 genomes, respectively, collected from different geographic regions. Chromosome pairing behavior was analyzed at metaphase I in 27 hybrids representing 23 hybrid combinations, and overall genomic relationships of the two target species with the other Elymus taxa were estimated. The study concluded that (i) interspecific hybridization was principally easy to perform between the Elymus species, but no general pattern of crossability was obtained, and all hybrids were completely sterile, (ii) the two species have a similar meiotic pattern in their hybrids with the other Elymus species, and (iii) species containing the SY, SYP, and SYH genomes have a generally higher level of genomic homology to the target species than those possessing the SH genomes, and the South American hexaploid with the SH1H2 genomes has the lowest level of genomic homology to the two target taxa.Key words: Elymus, interspecific hybridization, meiosis, genome, species relationship.
Rapid spread of a P element/Adh gene construct through experimental populations of Drosophila melanogaster
Authors: Meister G. A. , Grigliatti T. A.
Published: May 2008

Transposable elements may be potential tools for the dispersal of engineered DNA through target insect populations. The utility of this hypothesis is predicated on the ability of transposable elements carrying a large DNA insert to rapidly disperse through a population. In addition, the inserted DNA must be replicated with a high degree of fidelity during this dispersal. We have monitored the ability of a transposable element with an inserted gene to spread through experimental populations and tested whether the passenger gene retains its ability to encode an active protein. Several Drosophila melanogaster laboratory populations were initiated with female flies that were null for alcohol dehydrogenase activity and contained no P elements. Most of the females were mated to males of the same strain; however, 1 or 10% of the females were mated to males from a strain that had previously been transformed with a helper P element and a P element/Adh gene construct. The dispersal of P elements to new genomes was monitored at each generation by randomly selecting females and performing DNA hybridization assays on dissected ovarian tissue. In addition, each female was tested for alcohol dehydrogenase activity using a simple histochemical assay. We find that, despite an approximate threefold increase in size, the P element constructs containing a functioning gene are still capable of rapid dispersal through the experimental populations. We also show that many of the inserted Adh genes still encode an active product.Key words: P element, transformation, Adh, transposable element.
Evidence for Darwinian selection of the 2-μm plasmid STB locus in Saccharomyces cerevisiae
Authors: Rank G. H. , Xiao W. , Arndt G. M.
Published: May 2008

The 2-μm plasmid of industrial and laboratory strains of Saccharomyces cerevisiae exists as two main polymorphic forms designated type I and type II. Polymorphism is restricted to the 3200-bp right unique region where types I and II show approximately 10% nucleotide divergence in trans-acting REP1 and RAF loci and 30% divergence in the cis-acting STB locus. In addition, the cis-acting STB plasmid partition locus of type II plasmids varies in sequence and copy number of a 125-bp repeat. We devised chimeric and 2-μm plasmid stability experiments to evaluate the effect of STB polymorphism on plasmid fitness in amphiploid industrial and haploid laboratory strains. Reciprocal experiments of type-II STB chimeric plasmids in type-I bakers' yeast or a type-I chimeric plasmid in type-II distillers', wine, or haploid strains showed similar partition efficiencies. However, chimeric and 2-μm plasmids carrying a 250-bp STB from a type-II haploid strain had reduced fitness in a type-II industrial wine strain. These results in conjunction with molecular analyses of 2-μm-like and 2-μm plasmids indicates the coevolution of STB with trans-acting plasmid and host-cell factors.Key words: Saccharomyces cerevisiae, 2-μm plasmid, STB adaption.
Detection of rye chromosome 2R using the polymerase chain reaction and sequence-specific DNA primers
Authors: Lee J.-H. , Graybosch R. A. , Lee D. J.
Published: May 2008

Sequences derived from a rye gamma secalin gene were used as primers in polymerase chain reactions using DNA obtained from a series of wheat and triticale genetic stocks. A 473-bp fragment, the predicted size based on the distance between the selected primers, was found only in rye, triticales, and wheat lines carrying rye chromosome 2RS. Use of triticale lines with various wheat chromosome substitutions confirmed the chromosomal origin of the rye-specific marker. The presence of the 473-bp PCR product was always associated with the production of 75K secalins in grain samples. Thus, the primer sequences, and the clone of origin (pSC503), were both derived from the SEC-2 locus of rye chromosome 2RS.Key words: wheat (Triticum aestivum), rye (Secale cereale), chromosomal translocations, chromosomal substitutions, DNA polymerase chain reaction, sequence-specific primers.
Chromosomal localization and polymorphisms of ribosomal DNA in oat (Avena spp.)
Authors: Jellen E. N. , Phillips R. L. , Rines H. W.
Published: May 2008

The 17S/5.8S/26S ribosomal DNA (rDNA) sequences were mapped to the three satellited (SAT) chromosomes in the common hexaploid cultivated oat Avena sativa (2n = 6x = 42, AACCDD genomes). In situ hybridization and Southern hybridization of maize and (or) wheat rDNA probes to DNA from nullisomics derived from the cultivar 'Sun II' allowed the placement of rDNA sequences to the physical chromosomes. A restriction map was produced for the rDNA sequences of 'Sun II' using a maize probe from the transcribed region of the 17S/26S rDNA repeat. The set of rDNA repeats on SAT 2 of 'Sun II' possesses a 10.5-kb EcoRI fragment not found in the rDNA repeats of SAT 1 and SAT 8. This 10.5-kb fragment results from the absence of an EcoRI site in the intergenic spacer (IGS) of SAT 2 repeats. Extensive polymorphisms were demonstrated for three hexaploid Avena species, namely, the Mediterranean-type cultivated oat A. byzantina and the wild species A. sterilis and A. fatua. However, geographically diverse A. sativa cultivars displayed little rDNA variation. In contrast with all of the A. sativa cultivars examined, the A. sterilis accessions generally lacked the 10.5-kb EcoRI fragment. The results support the hypothesis that A. sativa accessions descend from a limited ancestral cultivated population. The rDNA polymorphisms are attributed to differences in lengths and restriction sites of the IGS.Key words: oats, rDNA, RFLPs, nullisomics, in situ hybridization.
Pachytene pairing and metaphase I configurations in a tetraploid somatic Lycopersicon esculentum × L. peruvianum hybrid
Authors: Sybenga J. , Schabbink E. , Eden J. van , Jong J. H. de
Published: May 2008

In the tetraploid somatic hybrid between the diploid Lycopersicon species L. esculentum (tomato) and L. peruvianum, synaptonemal complexes formed quadrivalents in 73 of the 120 sets of four chromosomes (60.8%) in 10 cells studied in detail at pachytene. Of these, 43 had one pairing partner exchange, 22 had two, and 8 had three, very close to a Poisson distribution. The points of pairing partner exchange were concentrated at the middle of the two arms. The frequency per arm corresponded with physical arm length. There was a sharp drop around the centromere, and pericentric heterochromatin had a slightly lower probability of being involved in pairing partner exchange than euchromatin. The chromosomes align before pairing and there are several points of pairing initiation, with concentrations at or near the ends and the centromere. From zygotene to late pachytene the quadrivalent frequency decreased considerably. At late pachytene it was lower than expected with the observed high frequency of pairing partner exchange. Pairing affinity between species was only slightly lower than affinity within species, in spite of considerable genetic differentiation. The frequency of recombination nodules increased from early to late zygotene and then decreased strongly to full pachytene. There is a highly significant negative correlation between percent pairing and SC length. At metaphase I the frequency of quadrivalents was 0.444, and branched quadrivalents were rare, probably caused by interference and restriction of chiasma formation to distal euchromatin. Metaphase I quadrivalent frequency is a relatively good indication of pairing affinity in this material.Key words: Lycopersicon, tetraploid hybrid, synaptonemal complex, pairing partner exchange, diakinesis/metaphase I.
Improved stability of genetic sex-separation strains for the Mediterranean fruit fly, Ceratitis capitata
Authors: Franz G. , Gencheva E. , Kerremans Ph.
Published: May 2008

In the existing genetic sexing strains for the medfly, Ceratitis capitata, male recombination leads to breakdown of the sexing mechanism under mass rearing conditions. The rate of breakdown depends on the recombination frequency and on the fitness of the recombinants. We have tested two different sexing genes, white pupa and a temperature sensitive lethal, in combination with the translocation T(Y;5)30C. Both sexing strains broke down, although at very different rates. In the case of the white pupa strain, 3.5% recombinants were observed after rearing the strain for 15 generations. The second strain, utilizing white pupa and the temperature sensitive lethal as selectable markers, already reached a comparable level after six generations and was broken down completely in the ninth generation. In these strains the frequency of recombination is high because the breakpoint of T(Y;5)30C and the sexing gene(s) are far apart. To remedy the situation, we have isolated four new translocations with breakpoints located closer to the sexing genes. Mass rearing was simulated for several generations with strains based on these translocations and no breakdown was observed under the conditions used.Key words: medfly, sterile insect technique, genetic sexing, recombination.
Linkage of genes conferring specific resistance to oat crown rust in diploid Avena
Authors: Gregory James W. , Wise Roger P.
Published: May 2008

The inheritance of resistance to an isolate of crown rust race 276 was investigated in four diploid oat lines. F3 families derived from Avena strigosa C.I. 2630 × Avena nuda C.I. 9009, Avena wiestii C.I. 1994 × Avena strigosa C.I. 3815, and C.I. 3815 × C.I. 2630 were inoculated at the seedling stage and evaluated 9–12 days later. Segregation of the F3 families indicated that C.I. 2630 and C.I. 3815 each possess one dominant gene that conditions resistance to race 276. The alleles conferring resistance occur at two different loci, separated by 17 cM on the same chromosome, and appear to be complementary. C.I. 3815 may have an additional recessive resistance allele at a different locus on the same chromosome, 19 cM from its other resistance gene locus.Key words: crown rust, oat, Avena strigosa, Avena wiestii, Avena nuda, Puccinia coronata.
Phylogenetic relationships of 10 grass species: an assessment of phylogenetic utility of the internal transcribed spacer region in nuclear ribosomal DNA in monocots
Authors: Hsiao C. , Chatterton N. J. , Asay K. H. , Jensen K. B.
Published: May 2008

Entire sequences of the internal transcribed spacers (ITSs) and 5.8S subunit of nuclear ribosomal DNA (nrDNA) were obtained from nine grass species by direct double-stranded sequencing of polymerase chain reaction (PCR) amplified DNA fragments. These sequences from subfamily Pooideae (Triticum aestivum, Crithodium monococcum, Sitopsis speltoides, Hordeum vulgare, Secale montanum, Avena longiglumis, Bromus inermis, Brachypodium distachyon) and subfamily Panicoideae (Sorghum bicolor) together with published ITS sequence of rice (Oryza sativa, Bambusoideae) were analyzed using Wagner parsimony (PAUP) and the neighbor-joining distance method to assess the phylogenetic utility of ITS sequences at various taxonomic levels. Among the aligned sequences that ranged from 588 to 603 nucleotides in length, 118 of 269 variable sites contained potential phylogenetic information. A member of Bromus, B. inermis, was the sister taxon to the Triticeae species. Brachypodium was more distantly related to Triticeae than was Bromus or Avena. These data, with Oryza sativa as the outgroup, indicate monophyly of the Pooideae species and of the members of the tribe Triticeae within Pooideae. Phylogenetic trees of the 10 grass species generated from the ITS sequence data were in general agreement with phylogenies based on molecular data from ribosomal RNA (rRNA) and chloroplast DNA (cpDNA) of similar grass taxa. This study reaffirms that sequences of the ITS region are useful for phylogenetic inference among closely related monocot species.Key words: Poaceae, Pooideae, Triticeae, DNA sequences, molecular phylogeny.
Identification of five new primary simple trisomies in soybean based on pachytene chromosome analysis
Authors: Ahmad F. , Hymowitz T.
Published: May 2008

Primary trisomics are ideal cytogenetic tools for associating genes and linkage groups to known chromosomes and testing their independence. In the cultivated soybean, only 8 of the possible 20 primary simple trisomics are known. In this report cytological evidence for the identification of five more new primary simple trisomics, corresponding to chromosomes 6, 8, 12, 16, and 19, is presented for the first time. The precise identification was based on trivalent configuration of chromosomes at the pachynema stage of meiosis, where the chromosomes were identified by their characteristic total length, arm ratio, and distribution of heterochromatin and euchromatin. Cytological observation of chromosome pairing in the 2n = 42 chromosome F1 plants, obtained from eight crosses between known primary trisomics, also supported the identification of primary trisomics in soybean based on pachytene chromosome analysis. Together with the eight primary trisomics identified previously, 13 of the possible 20 primary simple trisomics have been successfully identified, which accounts for about 76% of the total nuclear euchromatin in soybean.Key words: Glycine max, soybean, trisomic, pachytene chromosome, chromosome pairing.
cDNA sequence and tissue-specific expression of an anionic flax peroxidase
Authors: Omann Franz , Beaulieu Normand , Tyson Hugh
Published: May 2008

A flax (Linum usitatissimum L.) λgt10 cDNA library was screened with a probe coding for the amino terminus of a flax peroxidase. The probe was generated by PCR amplification of the library with one of the λgt10 sequencing primers and a mixed oligonucleotide derived from a well-conserved amino acid region (distal heme ligand) found in all plant peroxidases. A positive clone (FLXPER2) was isolated and characterized. The cDNA contains 1153 nucleotides, excluding the poly(A) tail, and encodes a mature protein of 297 amino acids with a molecular mass of 31.9 kDa. The mature protein's amino acid sequence contains three highly conserved regions, two of which contain histidine ligands for the heme group. The deduced amino acid sequence has nine cysteine residues. Eight are identically located to those of horseradish C peroxidase, which participate in four disulfide bridges; these cysteines are highly conserved in all plant peroxidases. One potential N-glycosylation site (Asn-X-Thr/Ser) is present. The predicted pI value of 4.5 identifies FLXPER2 as an anionic peroxidase. Northern blot analysis shows that its mRNA expression is unique to stem tissue. Amino acid sequence comparisons show high similarity between FLXPER2 and peanut, rice, and tobacco peroxidases.Key words: flax peroxidase cDNA, PCR, Northern analysis, sequence relationships.
How many additional parameters in a conversion model can be evaluated using "corresponding-site" events?
Authors: Fincham J. R. S.
Published: May 2008

Contrary to a recent claim by B.C. Lamb and S.A. Zwolinski (1992), the frequencies of "corresponding-site" conversion events (all four chromatids involved in conversion at the same locus in the same meiotic cell) can be used to evaluate only two parameters not otherwise calculable: a coincidence parameter and the frequency of conversion-type events in which a normal 1:1 ratio is restored.Key words: Ascobolus immersus, gene conversion.
Three spontaneous mutations at the albino locus in SELH/Bc mice
Authors: Juriloff D. M. , Porter S. D. , Harris M. J.
Published: May 2008

The SELH/Bc inbred mouse stock has produced an unusually high number of spontaneous mutations, including sph2Bc, nuBc, a recessive lens opacity, and three mutations at the c locus. Classical genetic and molecular genetic studies were done to investigate the origin of the albino locus mutations. Southern blots probed with the mouse tyrosinase cDNA showed that two of the mutations, cBc and c2Bc, are deletions of exons 1, 2 and 3. The third mutation, c3Bc, showed a disruption, either a rearrangement or an insertion, in the region of exon 1. The deletion of the cBc mutation is anticipated to be large as the mutation has inactivated the Mod-2 locus 2 cM away, and an essential locus for postimplantation survival outside the c–Mod-2 interval, whereas the c2Bc mutation is viable and fertile in homozygotes. Homozygotes for c3Bc are also viable and fertile. We conclude that at least some of the molecular events leading to the three albino mutations were independent. The mutations differ from each other and from the classical albino point mutation. All three new mutations originated from parents who were germline mosaics, and the mutational events were therefore all postmeiotic. All three mosaics shared one common ancestor six generations previously, raising the possibility that an instability of the albino locus might have been inherited. SELH/Bc mice may provide an animal model for the study of mechanisms underlying genetic instability.Key words: mutation, tyrosinase, mosaicism, deletion.
Influence of nuclear background on transcription of a chimeric gene (orf256) and coxI in fertile and cytoplasmic male sterile wheats
Authors: Song Jiasheng , Hedgcoth Charles
Published: May 2008

Crosses between Triticum timopheevi, as maternal donor, and T. aestivum can lead to cytoplasmic male sterile (cms) plants. The T. timopheevi derived mitochondrial DNA from parental, cms, and fertility-restored lines differs from that of T. aestivum derived mtDNA in the coxI gene region. Our previous results for cms lines showed that there is an open reading frame, orf256, upstream from coxI in T. timopheevi derived mtDNA that is not present in T. aestivum DNA. The 5′ flanking region and the first 33 nucleotides of the coding region of orf256 are identical to the corresponding region of T. aestivum coxI, whereas the rest of orf256, including the 3′ flank, is not related to coxI. Also, the organization of orf256 and coxI on a HindIII fragment from T. timopheevi derived mtDNA are identical in T. timopheevi, cms, and fertility-restored lines. We now report that the DNA sequence of orf256 is identical in T. timopheevi, cms, and fertility-restored lines. Major transcripts in cms and fertility-restored lines encode both orf256 and coxI with 5′ termini like coxI mRNA of T. aestivum, whereas parental mitochondria from T. timopheevi have major transcripts with 5′ termini within the orf256 coding region. Mitochondria from cms and fertility-restored lines have the potential to produce a protein that would not be present in parental T. timopheevi or in T. aestivum.Key words: cytoplasmic male sterility, wheat, mitochondrial DNA, mitochondrial RNA, coxI.
Construction of an RFLP map in sorghum and comparative mapping in maize
Authors: Pereira M.G. , Lee M. , Bramel-Cox P. , Woodman W. , Doebley J. , Whitkus R.
Published: May 2008

An F2 population derived from a cross between Sorghum bicolor ssp. bicolor ('CK60') and Sorghum bicolor ssp. drummondii ('PI229828') was used to develop an RFLP genetic linkage map of sorghum. The map consists of 201 loci distributed among 10 linkage groups covering a map distance of 1530 cM, with an average 8 cM between adjacent loci. Maize genomic probes (52), maize cDNA probes (124), and sorghum genomic probes (10) were used to define the loci (55, 136, and 10, respectively). Ninety-five percent of the loci fit expected segregation ratios. The loci with distorted segregation ratios were confined almost exclusively to a region of one linkage group. Comparison of sorghum and maize maps indicated high correspondence between the two genomes in terms of loci order and genetic distance. Many loci linked in maize (45 of 55) were also linked in sorghum. Instances of both conserved and rearranged locus orders were detected. Key words: genetics, gene mapping, Sorghum bicolor, Zea mays.
Resolution of populations of the Mediterranean fruit fly at the DNA level using random primers for the polymerase chain reaction
Authors: Haymer David S. , McInnis Donald O.
Published: May 2008

We have used the polymerase chain reaction (PCR) and the random amplified polymorphic DNA (RAPD) method to identify DNA polymorphisms that can be used as genetic markers to characterize populations of the Mediterranean fruit fly, Ceratitis capitata. In this study, RAPD markers have been used to resolve genetic variability between populations of this major agricultural pest species. The populations analyzed represent either laboratory stocks or wild collections originating from different geographic localities. Using the same set of individual flies from each of several populations, we show that the use of different primers in the RAPD method permits detection of different levels of population differentiation. We show results from RAPD primers (e.g., primer 14) that identify regions of the genome (through PCR amplification) that are essentially monomorphic in all flies originating from a particular geographic locality. We also show RAPD primers (e.g., primer 67) that identify what appear to be highly variable regions of the genome. We have used primers of this type to produce genetic markers that can distinguish even between laboratory versus wild populations as well as subpopulations of flies from more broadly defined geographic localities, such as within the Hawaiian islands. These results show that the RAPD method is a broadly applicable, high resolution method for documenting genetic variability within and between populations of insect pest species.Key words: RAPD–PCR, genetic markers, Ceratitis capitata, Mediterranean fruit fly populations.
RFLP diversity of common bean (Phaseolus vulgaris) in its centres of origin
Authors: Velasquez Viviana L. Becerra , Gepts Paul
Published: May 2008

Eighty-five wild and cultivated accessions of common bean (Phaseolus vulgaris L.), representing a wide geographic area in the centres of domestication were tested for restriction fragment length polymorphisms (RFLPs). Genomic DNA was digested with one of three restriction enzymes (EcoRI, EcoRV, and HindIII) and hybridized to 12 probes distributed throughout the common bean genome. Accessions could be classified into two major groups with a distinct geographical distribution in Middle America and the Andes. Within each gene pool, cultivated accessions clustered together with wild forms from the same geographical area supporting the multiple domestications hypothesis for this crop. Estimates of Nei's genetic distances among the cultivated races from the two different gene pools varied from 0.12 to 0.56 and among races from the same gene pool from 0.04 to 0.12, suggesting that the divergence in Phaseolus vulgaris has reached the subspecies level. The level of genetic diversity (Ht = 0.38) was twice the value obtained with isozyme analysis. Genetic diversity within races (Hs = 0.27) was four to five times higher compared with isozymes, but genetic diversity between races (Dst = 0.11) was similar for both categories of markers. These results corroborate previous studies on the characterization of genetic diversity in common bean that clearly showed two distinct gene pools, Middle American and Andean. Moreover, RFLP markers are superior to isozymes because they provide better coverage of the genome and reveal higher level of polymorphisms.Key words: common bean, restriction fragment length polymorphism, domestication, genetic diversity.
Genome size and base composition in Medicago sativa and M. truncatula species
Authors: Blondon François , Marie Dominique , Brown Spencer , Kondorosi Adam
Published: May 2008

The genome size (1C value) and base composition of 14 ecotypes of two species of tetraploid and diploid Medicago have been assessed by flow cytometry. These parameters vary both between and within species. The diploid annual Medicago truncatula Gaertn. had the smallest genome of the group studied (which also covered M. sativa L. subsp. sativa, M. sativa L. subsp. caerulea (Less. ex Ledeb.) Schmalh., M. sativa L. subsp. quasifalcata Sinsk., M. sativa L. subsp. × varia (Martyn) Arcangeli; however, its ecotypes revealed substantial intraspecific variation. The smallest M. truncatula genome observed was ecotype 108-1 with 1C = 0.49 pg and 38.1% GC and the largest was Jemalong with 1C = 0.57 pg and 38.6% GC. The degree of polysomaty in these Medicago was low, although in some tissues the frequency of cells with 4C nuclei reached 50%.Key words: Medicago, genome size, base composition, flow cytometry, symbiosis.
Comparison of nuclear ribosomal RNA genes among Solanum species and other Solanaceae
Authors: Borisjuk N. , Borisjuk L. , Petjuch G. , Hemleben V.
Published: May 2008

The organization of the nuclear-encoded 18S, 5.8S, and 25S ribosomal RNA genes (ribosomal DNA; rDNA) of 21 New World species from different sections of the genus Solanum, of two Old World Solanum species, and of representatives of other Solanaceae (Nicotiana, Atropa, Datura, Physalis, and Capsicum) was analyzed by restriction enzyme mapping using different rDNA specific hybridization probes. All Solanum species investigated exhibited rDNA repeats between 8.7 and 9.3 kb in length; the only exception was S. neorossii with a repeat length of 10.3 kb. Sequence heterogeneity was observed mostly in the intergenic spacer (IGS) region. Restriction sites for EcoRI and DraI in the spacer sequences were found to be characteristic for the New World species of the genus Solanum and for Lycopersicon esculentum. An additional XbaI site was detected in the spacer region of two nontuber-bearing species, S. brevidens and S. etuberosum (subsection Estolonifera Hawkes; series Etuberosa), as well as in the primitive tuber-bearing species of the series Pinnatisecta and Polyadenia (subsection Potatoe G.Don), thus demonstrating that these Mexican species are separated from the other tuber-bearing species but are closely linked to the nontuber-bearing Estolonifera group. Two EcoRI sites mapped at the 3′end of the 25S rRNA coding region seem to be characteristic for members of the Solanaceae; the first EcoRI site is apparently methylated in approximately 50% of the rDNA repeats. Southern hybridization with an IGS fragment of Solanum tuberosum as hybridization probe and nucleotide sequence analysis of the phylogenetically informative 3′ end of the 25S rDNA support the assumption that the New World species of the genus Solanum are closely related to Lycopersicon (tomato) in contrast with other Solanaceae investigated, Nicotiana, Atropa, Datura, Physalis, and Capsicum. Moreover, the New World potatoes and tomato appear to be more closely related to each other than potatoes and the Old World species Solanum nigrum and Solanum dulcamara.Key words: ribosomal DNA, intergenic spacer, methylation, evolutionary relationship, phylogeny.
Characterization of a translocation and its impact on fertility in the pig
Authors: Singh B. , Fisher K. R. S. , Yadav B. R. , Basrur P. K.
Published: May 2008

A chromosome anomaly originally detected in two intersex pigs and previously reported as a Robertsonian translocation was characterized, and its transmission pattern was assessed by analyzing the progeny and immediate relatives of a sow. Cytogenetic investigations on four phenotypically normal relatives of the intersexes, including a sow, showed that the rearrangement was a reciprocal translocation involving the X chromosome and an autosome. Giemsa-banding and reverse-banding techniques indicated that the break in the X chromosome may have occurred in the terminal segment of the short arm (Xp) and that in the autosome in the proximal segment of the acrocentric chromosome 14 (14q). Reverse-banding techniques also revealed that the normal X is the late-replicating X in female translocation carriers. Centromere banding revealed an intercalary band on the long arm of the submetacentric chromosome representing the altered X in translocation carriers. The translocation was designated as rcp (X;14) (p+;q−). Chromosome analysis on 45 of 72 live offspring of the carrier sow showed a 20:25 distribution of carriers to normal piglets, with a carrier to normal ratio of 5:13 among females and 15:12 among male piglets, indicating an overall reduction of females (18) compared with males (27). Male carriers from one litter at sexual maturity showed hypoplastic testes and no spermatozoa in their ejaculates or fluid aspirates from the cauda epididymis. Their seminiferous tubules were narrow, spermatogenesis was impaired, and pyknotic and giant nuclei were abundant in the germinal epithelium. Meiotic preparations showed no stage beyond pachytene, suggesting that the absence of spermatozoa in the ejaculates may be due to the arrest of cells at the pachytene stage.Key words: X-autosome translocation, subfertility, porcine chromosomes.
Genetic variability and segregation analysis in Glossina morsitans morsitans (Diptera: Glossinidae) using DNA fingerprinting
Authors: Blanchetot A. , Gooding R. H.
Published: May 2008

DNA hybridization, using the M13 sequence as a probe, was used to analyze the genetic variability in four inbred lines of the tsetse fly Glossina morsitans morsitans Westwood. An average of 11.2 bands (ranging from 2 to 10 kb) were found per fly. An average of nine loci were detected in each line; 40% of the loci were polymorphic and the mean heterozygosity per locus varied from 0.098 to 0.29. Averaging the data across the four inbred lines, the band sharing estimates were 82.5% in males and 81.2% in females, and the mean band frequency estimates were 0.71 and 0.70 for males and females, respectively. Segregation of fragments, determined in "three generation" pedigrees, conformed to expected Mendelian ratios and two of seven fragments studied were linked to an X chromosome marker gene, ocra (body color).Key words: Glossina morsitans morsitans, DNA hybridization, genetic variability, segregation analysis.
The testis-determining autosomal trait, Tda-1, of C57BL/6J is determined by more than a single autosomal gene when compared with DBA/2J mice
Authors: Biddle Fred G. , Eisner James R. , Eales Brenda A.
Published: May 2008

The putative Tda-1 or testis-determining autosomal trait of the C57BL/6J mouse strain came to attention when the Y chromosome from the poschiavinus variety of Mus musculus domesticus was introduced into C57BL/6J by backcross matings. The F1 generation expressed normal testis development in XY individuals with the poschiavinus Y chromosome. In the backcross and subsequent crosses to C57BL/6J females, XY individuals expressed ovaries bilaterally or various combinations of an ovotestis with a contralateral ovary or testis or bilateral ovotestes and a few had testes bilaterally. Some of the previous breeding data appeared to support the hypothesis that C57BL/6J had an autosomal recessive factor that differed from the poschiavinus strain and, in the homozygous state, caused incomplete testis development with the poschiavinus Y chromosome. Subsequent attempts to map the Tda-1 factor, using a recombinant inbred strain approach, failed to localize Tda-1 and this suggests it might map to different chromosomes depending on which strain pairs are used. We constructed two strains of C57BL/6J and DBA/2J that are congenic for the poschiavinus Y chromsome. In the C57BL/6J.Y-POS congenic strain, liability to express incomplete testis development is normally distributed and thresholds in development specify the probability (or areas under the normal distribution) of different classes of ovary, ovotestis, and testis combinations. Testis development is normal in the DBA/2J.Y-POS congenic strain. With the two congenic strains and their normal parental strains we were able to conduct standard crosses to examine the reciprocal F1 and four types of backcross generations to the C57BL/6J strain in which all XY individuals have the poschiavinus Y chromosome. The Tda-1 trait of C57BL/6J is recessive to DBA/2J, but the segregating backcross generations reject the single gene model.Key words: mouse, Y chromosome, gonadal hermaphrodites, primary sex determination.
A directed search for DNA sequences tightly linked to cereal cyst nematode resistance genes in Triticum tauschii
Authors: Eastwood R. F. , Lagudah E. S. , Appels R.
Published: May 2008

An improved system for identifying DNA sequences linked to a targeted region was developed by fractionating DNA sequences prior to polymerase chain reaction (PCR) analysis. In an attempt to identify DNA markers linked to a strong CCN resistance gene, Ccn-D1, in Triticum tauschii, DNA samples from individuals homozygous for resistance and susceptibility at the Ccn-D1 locus in a segregating progeny were bulked separately to produce "near isogenic" DNA pools. The polymerase chain reaction was employed to generate several DNA amplification products from each of the bulked DNA segregants using 240 random (RAPD) and 4 semirandom (consensus sequences of intron–splice junctions) primers. A DNA polymorphic fragment was apparent between the resistant and susceptible bulks using one of the semirandom primers. Hydroxylapatite chromatography of reannealed DNA (to Cot values > 100) was used to enrich low copy DNA sequences in the bulk DNA segregants (resistant and susceptible DNA pools). PCR analysis on the low copy enriched DNA pool increased the level of polymorphism detected between bulked segregants. One of the RAPD fragments present in only the resistant low copy DNA pool was cloned and mapped to the distal region of the long arm of chromosome 2D. By using the cloned RAPD fragment, csE20-2, to assay an RFLP locus in three independent F2 progenies, complete cosegregation was obtained with the Ccn-D1 locus. Joint segregation analysis from a genome-wide mapping of RFLP markers and a second CCN resistance in T. tauschii, Ccn-D2, showed this locus to be loosely linked to the proximal region of chromosome 2.Key words: gene targeting, low copy sequences, RAPD, RFLP, bulk segregants.
Amplification of DNA sequences in wheat and its relatives: the Dgas44 and R350 families of repetitive sequences
Authors: McNeil D. , Lagudah E. S. , Hohmann U. , Appels R.
Published: May 2008

The sequence of a Triticum tauschii genomic clone representing a family of D-genome amplified DNA sequences, designated Dgas44, is reported. The Dgas44 sequence occurs on all chromosomes of the D genome of wheat, Triticum aestivum, and in situ hybridization revealed it to be evenly dispersed on all seven chromosome pairs. An internal HindIII fragment of Dgas44, designated Dgas44-3, defines the highly amplified region that is specific to the D genome. The polymerase chain reaction was used to amplify a 236-bp fragment within Dgas44-3 from chromosomes 1D, 2D, 3D, 4D, 5D, and 7D, and identical copies of this region of the Dgas44-3 sequence were found among the isolates from each of the chromosomes. The Dgas44-3 sequence population from specific chromosomes differed on average by 0.22% from the original Dgas44 sequence. The Dgas44 sequence was found to differentiate between the D genome present in T. aestivum, T. tauschii, hexaploid T. crassum, T. cylindricum, T. ventricosum, in which the sequence was present in a highly amplified form and T. juvenale, T. syriacum, and tetraploid T. crassum where the sequence family was difficult to detect. Another class of amplified sequences previously considered to be rye "specific." R350, was isolated from tetraploid wheat and its dispersed distribution on chromosomes was similar to the Dgas44 family in T. tauschii. In contrast with the Dgas44 sequence family, genome specificity for the remnant R350 sequence family was not evident since it was present on all wheat chromosomes.Key words: D genome, sequence amplification, in situ hybridization.
Comparison of somatic and sexual Brassica napus – Sinapis alba hybrids and their progeny by cytogenetic studies and molecular characterization
Authors: Chevre A. M. , Eber F. , Margale E. , Kerlan M. C. , Primard C. , Vedel F. , Delseny M. , Pelletier G.
Published: May 2008

Reciprocal crosses were performed between Brassica napus (AACC, 2n = 38) cv. Brutor and Sinapis alba (SalSal, 2n = 24) cv. Carine. Using fertilized ovary culture, 2.2 and 1.9% of interspecific hybrids were produced when white mustard was the female and the male parent, respectively. On S. alba cytoplasm, three plants with a BC1-like structure (SalSalAC, 2n = 43) were obtained and ACSal (2n = 31) and AACCSal (2n = 50) hybrids on reciprocal crosses. At the same ploidy level, no differences in meiotic behavior were observed. The amphidiploids (AACCSalSal, 2n = 62), produced after colchicine treatment of ACSal hybrids, were compared with the somatic hybrids previously obtained from the same parental varieties. Only two somatic hybrids differed and one of them lost Idh-2 rapeseed isozymes, whereas all the plants presented an hybrid pattern for all the other molecular markers. The plants with 50 chromosomes (AACCSal) from sexual hybrids were similar whatever their origins. Their comparison with back-cross progeny of somatic hybrids revealed that the latter one differed either by chromosome number, ranging from 42 to 54, or by the percentage of cells with less than 12 univalents and with multivalents. From our results, the efficiency of protoplast fusion compared with sexual crosses as a tool to introduce new traits in a crop is discussed.Key words: Brassica napus, Sinapis alba, somatic and sexual hybrids, meiotic behavior, molecular markers.