bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid genomic changes in newly synthesized amphiploids ofTriticumandAegilops. II. Changes in low-copy coding DNA sequences
Authors: Liu B , Vega J M , Feldman M
Published: April 2011

We recently reported that formation of allopolyploid wheat was accompanied by rapid nonrandom changes in low-copy noncoding DNA sequences. In this report we show that following allopolyploidization, changes also occurred in coding sequences. Genomic DNA of nine different newly synthesized amphiploids of different ploidy levels and their parental lines was digested with five restriction enzymes and probed with 43 coding sequences. The sequences, 19 genomic and 24 cDNA sequences, are group (homoeologous) specific and represent the proximal and distal regions of the short and long arms of the seven homoeologous groups of the Triticeae. We revealed three types of changes: disappearance of a parental hybridization fragment(s), appearance of a novel fragment(s), and simultaneous disappearance of a parental fragment(s) and appearance of a novel fragment(s). No elimination of sequences took place, since in every sequence studied the parental hybridization fragments were present in at least one of the enzyme digests. Variations in pattern among individual plants of the same amphiploid, as well as between several synthetic and natural amphiploids, indicated that at least some of the genomic changes occurred at random. Intergenomic recombination was not the cause of the observed changes. Evidence was obtained, however, that changes were also brought about by DNA methylation. Methylation may cause inactivation of genes or modify their expression levels in some of the newly synthesized amphiploid plants, leading to genetic diploidization and gene-dosage compensation and thus increasing variation among individuals.Key words: wheat, allopolyploidy, DNA methylation, genetic diploidization, genome evolution, group (homoeologous) specific sequences.
Mytilus protamine-like sperm-specific protein genes are multicopy, dispersed, and closely associated with hypervariable RFLP regions
Authors: Heath Daniel D , Hilbish Thomas J
Published: April 2011

Protamine-like sperm packaging proteins replace somatic histones during spermatogenesis, and although the proteins have been well-characterized in many marine invertebrate species, little is known of the arrangement of the genes. The research described here was designed to determine the sequence and structure of the protamine-like PL-III (or "1") gene in marine mussels (Mytilus spp). The PL-III sequence was found to be extremely variable not only among the closely related Mytilus species, but also within species and populations. The variation observed among eight PL-III sequences from a single individual indicated that PL-III was probably multiple-copied. Southern analysis confirmed that PL-III, and another protamine-like gene, (PL-II), were multicopy and dispersed, as well as associated with a hypervariable element. Some PL-III genes are also arranged in nontandem clusters, and the spacer regions are probably the source of the hypervariable nature of the Southern blots. The arrangement of the protamine-like genes in Mytilus appears to be closer to that reported for histones than protamines; however, their association with a hypervariable element is novel.Key words: mussels, histones, protamine, gene sequence, Southern blot.
Primed in situ labeling (PRINS): a method for rapid identification and quantification of human chromosomes in both lymphocytes and sperm nuclei
Authors: Musio Antonio , Baroli Paolo , Sbrana Isabella
Published: April 2011

In this work, a specific primer for X alphoid satellite DNA was used to detect chromosome X through primed in situ labeling (PRINS). The method allows the rapid identification of chromosome X in metaphase and its quantification in interphase. PRINS is equally applicable to both lymphocytes and sperm nuclei.Key words: PRINS, human sperm, chromosome X.
Genetic linkage maps of the ground crickets Allonemobius fasciatus and Allonemobius socius using RAPD and allozyme markers
Authors: Chu Jiming , Howard Daniel J
Published: April 2011

The ground crickets, Allonemobius fasciatus and A. socius are sister species and form a mosaic hybrid zone in the eastern United States. In this study, we developed RAPD markers and constructed genetic linkage maps for the two species, as a first step toward mapping quantitative trait loci that control conspecific sperm precedence. The A. fasciatus map consists of 25 markers mapped to 8 linkage groups, spanning 400.1 contiguous centiMorgans (cM). The average distance between two framework markers is 23.5 cM. The A. socius map consists of 20 markers mapped to 6 linkage groups, spanning 400.5 contiguous cM. The average distance between two framework markers is 30.4 cM. A sex chromosome was identified in the A. socius map. These are the first reported genetic linkage maps for Orthoptera.Key words: Allonemobius, allozyme, cricket, hybrid zone, linkage maps, RAPD.
Fertility of somatic hybrids Solanum commersonii (2x, 1EBN) (+) S. tuberosum haploid (2x, 2EBN) in intra- and inter-EBN crosses
Authors: Carputo D , Garreffa P , Mazzei M , Monti L , Cardi T
Published: April 2011

Solanum commersonii (+) S. tuberosum hybrids with different endosperm balance numbers (EBN) and ploidy were used in various crossing schemes with 4EBN S. tuberosum cultivars and a 3EBN somatic hybrid to test their behavior in intra- and inter-EBN crosses and to derive a BC1 population for potato breeding. The somatic hybrids included 12 tetraploids (2n = 48, 3EBN), 18 hypotetraploids (2n = 43-47, 3EBN), 2 hexaploids (2n = 72, 4 or 5EBN), and 5 hypohexaploids (2n = 63-70, 4 or 5EBN). The results confirmed that in the potato, EBN is more important than actual ploidy in determining the success or failure of crosses. Indeed, crosses between some hypohexaploid hybrids and S. tuberosum cultivars gave the highest number of viable seeds per berry, and seed viability was similar to that of intra-EBN crosses between varieties. Inter-EBN crosses demonstrated that exceptions to the 2:1 maternal-paternal EBN ratio in the hybrid endosperm can sometimes be tolerated. However, an excess in maternal EBN dosage was better tolerated than an excess in paternal EBN.Key words: EBN, ploidy, potato, Solanum commersonii, somatic hybrids.
Nonallelic noncomplementation models in mice: The first arch and lidgap-Gates mutations
Authors: Harris M J , Juriloff D M
Published: April 2011

We tested for complementation between two Mendelian mutations in mice, Far (first arch) and lgGa (lidgap-Gates). Each of these mutations gives greater than 70% risk of the birth defect, open eyelids, in homozygotes and gives little or no risk in heterozygotes. Far and lgGa are known to not be alleles; Far maps to Chr 2 and lgGamaps to Chr 13. However, the cross between +/Far (on the BALB/cGaBc strain) and lgGa/lgGa (on the LGG/Bc strain) gave 32% (48/149) of progeny affected with open eyelids at birth: 63% (45/71) of the double heterozygote, +/Far, +/lgGa, compared with 4% (3/78) of the +/+, +/lgGa progeny. That is, the complementation test suggests that Far andlgGa are alleles, whereas the mapping data show that they are not. We interpret the result of the Far by lgGa test as an example of nonallelic noncomplementation (or "false allelism") in mammals, and suggest that this phenomenon might be expected because open eyelids at birth involves a developmental threshold. Our data also show that both the embryonic and the maternal background genotypes strongly influence the risk of open eyelids in the Far by lgGa crosses. The risk to the double heterozygote (+/Far, lgGa) is highest (77%) with Far from the BALB/cGaBc rather than the ICR/Bc (0%) strain and in a BALB/cGaBc (77%) rather than an LGG/Bc (50%) dam in the reciprocal cross. This effect of genetic context on risk is also predicted by the threshold model. Based on our data on open eyelids at birth, we suggest that false allelism may be common in mammalian birth defects that result from failure to meet developmental thresholds, even when the "causal" mutations are Mendelian.Key words: digenic, false allelism, open eyelids, Far, threshold.
Cytogenetic analysis of Malpighian tubule polytene chromosomes of Culex pipiens (Diptera: Culicidae)
Authors: Zambetaki Anna , Pasteur Nicole , Mavragani-Tsipidou Penelope
Published: April 2011

A simple technique is described for obtaining well-spread and readable Malpighian tubule polytene nuclei of Culex pipiens on a routine basis. Detailed polytene chromosome maps are presented with a description of the most prominent landmarks of each chromosome, the regions with asynapsis and the most frequent weak points identified in the polytene arms. Usable Malpighian tubule polytene chromosomes should facilitate molecular cytogenetic, genetic, and potentially biosystematic studies on this medically important global vector of viral inducing encephalitis.Key words: Culex pipiens, polytene chromosomes, Malpighian tubules, banding pattern, photomap.
Application of fiber-FISH in physical mapping of Arabidopsis thaliana
Authors: Jackson Scott A , Wang Ming Li , Goodman Howard M , Jiang Jiming
Published: April 2011

Arabidopsis thaliana has become a model plant species for genetic studies because of its small genome and short juvenility period. However, the small chromosomes of this species are not suitable for classical cytogenetic studies. Here we demonstrate that the fluorescence in situ hybridization (FISH) technique using extended DNA fibers can be a powerful tool in the physical mapping of the A. thaliana genome. Using a refined fiber-FISH technique we were able to measure DNA clusters as long as 1.71 Mb, more than 1% of the A. thaliana genome. Several small DNA loci, including the telomeres and a dispersed repetitive DNA sequence, mi167, were also analyzed with this technique. The results show that without known adjacent DNA markers such small DNA loci cannot be mapped precisely using fiber-FISH. One of the most difficult obstacles in physical mapping by contig assembly is closing the gaps that are present between adjacent contigs. Currently available molecular techniques are not sufficient to accurately estimate the physical sizes of these gaps. We isolated bacterial artificial chromosome (BAC) clones bordering gaps 2 and 3 on the physical contig map of A. thaliana chromosome II. The BAC clones were used in fiber-FISH analysis and the physical sizes of the two gaps were estimated as 31 kb and more than 500 kb, respectively. Thus, we have demonstrated that fiber-FISH is an efficient technique for determining the physical size of gaps on molecular contig maps. Key words: fluorescence in situ hybridization, DNA fibers, physical mapping, genome analysis.
Effects of restriction endonucleases on nucleolar organizing regions in the ant Tapinoma nigerrimum
Authors: Lorite P , Palomeque T
Published: April 2011

The effects of some restriction endonucleases (REs) on the nucleolar organizing regions and on the genes for ribosomal RNA (rDNA) were analyzed using the nucleolar organizing region of the chromosome 6 of Tapinoma nigerrimum as an experimental model, since, in accordance with previous studies, the genes for ribosomal RNA seem to be present only in this chromosome. In situ non-digestion of the nucleolar organizing region was observed when EcoRI and HindIII were used. However, very evident digestion and partial digestion respectively were observed when HaeIII and Tru9I were used. Southern blot analysis realized on naked DNA digested with the same REs and using rDNA of Drosophila melanogaster as probe showed that there are target sequences for these enzymes in the rDNA. In accordance with the results obtained, the rDNA is poor in EcoRI and HindIII sequences, contains moderate amounts of Tru9I sequences, and is rich in HaeIII sequences. All the data obtained suggest that in the nucleolar organizing region of Tapinoma nigerrimum, the major, if not the only, limiting factor affecting in situ digestion by the REs used is the presence and frequency of their specific restriction targets. Consequently, extraction of DNA from this chromosome region depends on the size of the fragments originated.Key words: chromosome banding, Formicidae, NORs, rDNA, restriction endonucleases.
A set of conserved PCR primers for the analysis of simple sequence repeat polymorphisms in chloroplast genomes of dicotyledonous angiosperms
Authors: Weising Kurt , Gardner Richard C
Published: April 2011

Short runs of mononucleotide repeats are present in chloroplast genomes of higher plants. In soybean, rice, and pine, PCR (polymerase chain reaction) with flanking primers has shown that the numbers of A or T residues in such repeats are variable among closely related taxa. Here we describe a set of primers for studying mononucleotide repeat variation in chloroplast DNA of angiosperms where database information is limited. A total of 39 (A)n and (T)n repeats (n [Formula: see text] 10) were identified in the tobacco chloroplast genome, and DNA sequences encompassing these 39 regions were aligned with orthologous DNA sequences in the databases. Consensus primer pairs were constructed and used to amplify total genomic DNA from a hierarchical set of angiosperms. All 10 primer pairs generated PCR products from members of the Solanaceae, and 8 of the 10 were also functional in most other angiosperm species. Levels of interspecific polymorphism within the genera Nicotiana, Lycopersicon (both Solanaceae), and Actinidia (Actinidiaceae) proved to be high, while intraspecific variation in Nicotiana tabacum, Lycopersicon esculentum, and Actinidia chinensis was limited. Sequence analysis of PCR products from three primer pairs revealed variable numbers of A, G, and T residues in mononucleotide arrays as the major cause of polymorphism in Actinidia. Our results suggest that universal primers targeted to mononucleotide repeats may serve as general tools to study chloroplast variation in angiosperms.Key words: genetic markers, chloroplast genome, microsatellites, consensus primers, angiosperms.
An example of microsatellite length variation in the mitochondrial genome of conifers
Authors: Soranzo N , Provan J , Powell W
Published: April 2011

In the present study, the intergenic region between the mitochondrial genes encoding subunit 3 of NADH dehydrogenase (nad3) and ribosomal protein S12 (rps12) was shown to contain a Gn mononucleotide microsatellite repeat. This region was analysed in 15 species belonging to the genus Pinus and interspecific variation was detected in the form of repeat length polymorphism. Sequence analysis of a 576-bp region containing the microsatellite confirmed that the variability was due to expansion and contraction of the repeat motif and that no point mutations were present in the coding regions of the two genes. This is the first report of the occurrence of a microsatellite polymorphism in plant mitochondria.Key words: mitochondrial, microsatellite, Pinus, hard pines, taxonomy.
Chromosomal characterization and physical mapping of the 5S and the 18S-5.8S-25S ribosomal DNA in Helianthus argophyllus, with new data from Helianthus annuus
Authors: Cuéllar T , Orellana J , Belhassen E , Bella J L
Published: April 2011

The characterization of the mitotic chromosomes of Helianthus argophyllus by means of Feulgen staining, Giemsa C-banding, and the usual DNA sequence-specific fluorochromes allows a chromosomal classification of this species, and shows that two kinds of heterochromatin co-exist equilocally in its chromosomes. One type is confined to the pericentromeric areas of all the chromosomes and the other is associated with the secondary constrictions of the satellite chromosomes. This species is evolutionarily very close to H. annuus with which it is involved in introgression breeding programs. Since these two species show no intra- or interspecific differences with the above treatments, we have used C-banding followed by DAPI, chromomycin A3 or Acridine Orange, and the fluorescent in situ hybridization (FISH) with 5S and 18S-25S ribosomal DNA probes to characterize further the chromosomes of both species in an attempt to find practically applicable chromosomal markers. Our results confirm the heterogeneity of the heterochromatin in these species and show that neither its distribution nor its response to distinct fluorochrome treatments allows better discrimination of the chromosomes within or between the species. On the other hand, the 18S-5.8S-25S rDNA arrays are located in the secondary constrictions of the satellited SM7, SM10, and ST13 pairs and the 5S-rDNA genes are interstitially placed on the short arm of the SM7 and SM11 chromosomes in both species. This permits these chromosomes to be distinguished and provides markers which may be helpful for further physical mapping of DNA sequences in these species.Key words: chromosome banding, sunflower cytogenetics, heterochromatin, ribosomal DNA mapping, FISH.
Copia-SSR: A simple marker technique which can be used on total genomic DNA
Authors: Provan J , Thomas WTB , Forster B P , Powell W
Published: April 2011

We have developed a PCR-based assay which uses a combination of two classes of repetitive elements found in eukaryotic genomes, namely Ty1-Copia retrotransposons and simple sequence repeats, to amplify multiple polymorphic products from total genomic DNA. Using the technique, seven markers were mapped to four different chromosome arms using a barley doubled haploid mapping population. This technique offers a simple and efficient method of generating both dominant and codominant genetic markers in virtually any eukaryote for mapping and diversity studies.Key words: Copia-SSR, microsatellite, retrotransposon, barley, genotyping.
Sequence-tagged microsatellite site markers for chickpea (Cicer arietinumL.)
Authors: Hüttel Bruno , Winter Peter , Weising Kurt , Choumane Wafa , Weigand Franz , Kahl Günter
Published: April 2011

Two small-insert genomic libraries of chickpea (Cicer arietinum L.) were screened with a set of microsatellite-specific oligonucleotide probes. A total of 121 positive clones were identified among 13 000 plated colonies. Thirty-nine clones were recognized by (TAA)5, 26 by (GA)8, 18 by (GT)8, 27 by a pool of AT-rich trinucleotide repeats [(CAA)5, (CAT)5, and (GAA)5], and 11 by a pool of GC-rich trinucleotides [(TCC)5, (CAC)5, (CAG)5, and (CGA)5]. Of 53 clones selected for sequencing, 43 carried a microsatellite. Flanking primer pairs were designed for 28 loci, and used on a small test-set comprising one C. reticulatum and four C. arietinum accessions. Separation of the PCR products on agarose or polyacrylamide gels revealed single bands of the expected size with 22 of the primer pairs. Sixteen of these "Cicer arietinum sequence-tagged microsatellite site" (CaSTMS) markers were polymorphic at an intraspecific level, detecting 2-4 alleles within the four accessions examined. Primer pairs CaSTMS10 and CaSTMS15 revealed 25 and 16 alleles among 63 C. arietinum accessions from different geographic locations, reflecting gene diversity values of 0.937 and 0.922, respectively. Mendelian inheritance of CaSTMS markers was demonstrated using a set of recombinant inbred lines and their parents.Key words: chickpea, molecular markers, STMS, microsatellites, DNA polymorphism.
Prospects for introgressing tomato chromosomes into the potato genome: An assessment through GISH analysis
Authors: Garriga-Calderé F , Huigen D J , Jacobsen E , Ramanna M S
Published: April 2011

With a view to assess the possibility of homoeologous pairing and crossing-over between the chromosomes of potato (Solanum tuberosum) and tomato (Lycopersicon esculentum), a somatic fusion hybrid and two monosomic alien tomato addition genotypes were investigated through genomic in situ hybridisation (GISH). The somatic fusion hybrid, C31-17-51, was near hexaploid (2n = 6x - 4 = 68) possessing 46 potato chromosomes + 20 tomato chromosomes + 2 translocated chromosomes. The two alien addition genotypes were near tetraploids (2n = 4x + 1 = 49) and consisted of monosomic alien additions for tomato chromosome 1 in genotype 2103-1, and tomato chromosome 8 in genotype 2301-2. In the fusion hybrid the tomato pachytene chromosome identification revealed that the chromosomes 1, 2, 5, 6, 7, 10, and 12 were in diploid condition whereas among those that were in haploid condition, three could be identified viz., 4, 9, and 11. The remaining three chromosomes could not be cytologically identified. Although the chromosomes with translocated segments could not be identified at the pachytene stage due to technical difficulties, there was clear evidence for the presence of a reciprocal translocation observed at diakinesis and metaphase I stages. Because of autosyndetic pairing of the translocated segments, it gave a false impression as if there was a high frequency (86.0%) of allosyndetic pairing. In contrast to the fusion hybrid, the two alien monosomic addition genotypes showed a very low frequency of allosyndetic pairing, namely 1.1 and 1.3% respectively for the monosomic additions 1 and 8. In the genotype 2301-2, monosomic addition for tomato chromosome 8, crossing-over between the homoeologous chromosomes was estimated to occur in 0.8% of the meiotic cells investigated. Despite this low frequency of homoeologous pairing and crossing-over, there is a possibility for introgressing tomato chromosomal DNA into the potato genome through intergenomic recombination.Key words: Solanum, Lycopersicon, chromosome additions, GISH, introgression.
Integration of a molecular linkage group containing the broomrape resistance gene Or5 into an RFLP map in sunflower
Authors: Lu Yun Hai , Gagne Geneviève , Grezes-Besset Bruno , Blanchard Philippe
Published: April 2011

A linkage group containing the Or5 gene conferring resistance to Orobanche cumana race E, as well as 5 SCAR markers and 1 RAPD marker has been recently identified in sunflower. A SCAR marker RTS05, mapped 5.6 cM proximal to the Or5 locus, was analysed in an F2 population for which the segregation data of 80 RFLP markers (GIE cartisol - Phase II, France) were available. An association was found between the SCAR marker RTS05 and an RFLP marker S009 (32.1 cM, LOD = 4.7) that had been mapped to the linkage group 17 of the GIE Cartisol RFLP map. Another RFLP marker S010, tightly linked to S009 (0.0 cM) in the same linkage group, was screened in the F2 population that had been previously used for the Or5 linkage map identification. S010 was found to be significantly linked to all 5 SCAR markers as well as to the single RAPD marker with a LOD > 3.0 in each case. This RFLP marker was mapped between two SCAR markers and was situated at 35.1 cM from the resistance gene with a LOD = 2.7. These results showed that the Or5 linkage group could be integrated with the linkage group 17 of the GIE Cartisol RFLP map.Key words: Helianthus, Orobanche, RFLP, SCAR, linkage map.
A twenty strain survey and backcross localization of the erythrocytic GTP concentration determining locus Gtpc on mouse chromosome 9
Authors: Wiebe G J , Fung E , Biddle F G , Snyder F F
Published: April 2011

Erythrocyte nucleotide concentrations were surveyed among 20 inbred strains of mice in order to further assess the variability in GTP concentration. There was no significant difference in erythrocytic ATP concentration (Scheffé's test at P = 0.01), 678-1154 nmol/mL packed cells, among the strains surveyed. Two groups were distinguishable with respect to erythrocytic GTP concentration, 8 strains having high GTP, 215 ± 44 nmole/mL packed cells, and 12 strains having low GTP, 34 ± 12 nmole/mL packed cells. The erythrocytic GTP concentration determining trait Gtpc was previously shown to be linked to transferrin, Trf, on chromosome 9. Analysis of 232 [(B6 × WB) F1 × B6] backcross individuals for Gtpc and 8 microsatellite markers restricted the localization of Gtpc to a 5.6 ± 2.1 cM region. The gene order and genetic distances in cM ± SE are: (D9Mit14) 0.4 ± 0.4 (D9Mit24) 1.7 ± 0.8 (Gtpc, D9Mit51, D9Mit116, D9Mit212) 3.9 ± 1.3 (D9Mit200) 3.0 ± 1.1 (D9Mit20) 7.8 ± 1.8 (D9Mit18). The GTP concentration determining trait appears to be a property of erythrocytes as no differences were observed for GTP/ATP ratios of brain, kidney, liver, and tongue from a low GTP strain, C3H/HeHa × Pgk-1a and a high GTP strain, C57BL/6J.Key words: Gtpc, guanosine-5'-triphosphate, GTP, mouse, chromosome 9.
A subtelomeric satellite DNA family isolated from the genome of the dioecious plant Silene latifolia
Authors: Garrido-Ramos M A , de la Herrán R , Rejón M Ruiz , Rejón C Ruiz
Published: April 2011

In an ongoing effort to trace the evolution of the sex chromosomes of Silene latifolia, we have searched for the existence of repetitive sequences specific to these chromosomes in the genome of this species by direct isolation from low-melting agarose gels of satellite DNA bands generated by digestion with restriction enzymes. Five monomeric units belonging to a highly repetitive family isolated from Silene latifolia, the SacI family, have been cloned and characterized. The consensus sequence of the repetitive units is 313 bp in length (however, high variability exists for monomer length variants) and 52.9% in AT. Repeating units are tandemly arranged at the subtelomeric regions of the chromosomes in this species. The sequence does not possess direct or inverted sequences of significant length, but short direct repeats are scattered throughout the monomer sequence. Several short sequence motives resemble degenerate monomers of the telomere repeat sequence of plants (TTTAGGG), confirming a tight association between this subtelomeric satellite DNA and the telomere repeats. Our approach in this work confirms that SacI satellite DNA sequences are among the most abundant in the genome of S. latifolia and, on the other hand, that satellite DNA sequences specific of sex chromosomes are absent in this species. This agrees with a sex determination system less cytogenetically diverged from a bisexual state than the system present in other plant species, such as R. acetosa, or at least a lesser degree of differentiation between the sex chromosomes of S. latifolia and the autosomes.Key words: satellite DNA, sex chromosomes, Silene latifolia, subtelomeric sequences.
The pattern of homoeologous recombination in triploid hybrids ofLolium multiflorumwithFestucapratensis
Authors: Zwierzykowski Z , Lukaszewski A J , Naganowska B , Lesniewska A
Published: April 2011

Homoeologous chromosomes of Lolium-Festuca hybrids are capable of frequent meiotic pairing and recombination. The frequency and distribution of recombination was studied by genomic in situ hybridization in backcross progenies of reciprocal triploid hybrids of Lolium multiflorum with Festuca pratensis. Significant differences in the male transmission of the parental and translocated chromosomes were observed depending on the cytoplasm of the F1hybrids and the ploidy level of the female test cross partner. The frequency of intergeneric translocations in the progeny indicated that, on average, there must have been at least 4.5 homoeologous arms paired in the F1hybrids; the actual frequency might have been higher because of pre- or post-zygotic selection against the F. pratensis chromatin, which probably eliminated certain gametes with Festuca-Lolium translocations. Both parental species are known for localized distal chiasmata, but the intergeneric translocation breakpoints were distributed along the entire lengths of the chromosome arms. The change in the distribution of homoeologous recombination might have been related to different pairing initiation of homologues and homoeologues. It probably resulted from allocation of additional chiasmata to chromosome arms and produced a net increase in recombination.Key words: homoeologous exchanges, Lolium-Festuca, translocations, recombination.
A cytological study of pretreatments used to improve isolated microspore cultures of wheat (Triticum aestivum L.) cv. Chris
Authors: Hu Tianci , Kasha Ken J
Published: April 2011

Isolated microspores of wheat can be induced in vitro to switch their development from the gametophytic pollen pathway to a sporophytic pathway, resulting in embryoid or callus formation. The influence of cold or mannitol pretreatment on karyokinesis and cytokinesis in isolated microspore culture responses were investigated. Anthers were pretreated in mannitol for 7 d at 28°C; spikes at 4°C for 28 d. Microspores often completed the 1st mitotic nuclear division during pretreatment while cytokinesis was delayed. During mannitol pretreatments, the 1st mitotic nuclear division was mostly symmetrical while only asymmetric 1st nuclear divisions were seen during or after cold pretreatment. Following the symmetrical division, the two similar nuclei often appeared to fuse to form a diploid nucleus. Subsequently, these nuclei underwent rapid nuclear divisions to form multinucleate, and later, multicellular structures in induction medium. Cold pretreatments also induced muticellular structures but frequencies were lower than after mannitol. A novel pretreatment of spikes, combining 0.4 M mannitol solution at 4°C for 4 d, delayed the 1st nuclear division, keeping all microspores in a haploid uni-nucleate stage and resulted in higher induction frequencies. The proportion of embryos larger than 2 mm that developed into green plants was as high as 70% when transferred to regeneration media. Ninety-five percent of the plantlets transferred from culture to soil survived. The improved pretreatment enhanced the potential of isolated microspore culture in wheat for plant breeding by producing large numbers of plants and for gene transformation by maintaining a uniform population of haploid uni-nucleate stage microspores as targets.Key words: wheat, pretreatment, karyokinesis, embryogenesis, microspore, cold, mannitol.
Mapping of duplicate genes in soybean
Authors: Lee Jennifer M , Bush Arla L , Specht James E , Shoemaker Randy C
Published: April 2011

Appressed pubescence genes in soybean cause hairs on the upper surface of leaves to lie flat, while pubescence remains erect elsewhere on the plant. For decades this trait was believed to be controlled in soybean by duplicated single genes, Pa1 and Pa2. However, reports in the literature conflicted as to which phenotype was dominant or recessive. Two populations were developed, each approximately 100 individuals, and each segregating for one of the appressed pubescence genes. A combination of SSRs (simple sequence repeats) and RFLPs (restriction fragment length polymorphisms) were used in each of these populations to map the independent genes. Two-point analysis weakly linked Pa1 and Pa2 to separate linkage groups. Lack of strong linkage suggested the trait may not be controlled by single genes. When QTL (quantitative trait loci) analysis was performed, one major locus and several minor loci were detected in each population. We report the mapping of the genes controlling appressed pubescence in soybean and their placement in homologous regions. Although appressed pubescence was originally reported to be single duplicate genes, we report that it is actually a more complex phenotype with major duplicated genes and minor modifying genes. These results offer interesting implications regarding the evolution of duplicate genetic factors and the definition of qualitative traits.Key words: homoeologous, Glycine, evolution, appressed pubescence, quantitative genetics.
Cytogenetic differentiation between Palearctic and Nearctic populations of Chironomus plumosus L. (Diptera, Chironomidae)
Authors: Butler Malcolm G , Kiknadze Iya I , Golygina Veronica V , Martin Jon , Istomina Albina G , Wülker Wolfgang F , Sublette James E , Sublette Mary F
Published: April 2011

Macrogeographic patterns of polytene chromosomal banding sequences were studied in natural populations of the Holarctic species Chironomus plumosus. Of the 31 inversion sequences now known, 16 are endemic to the Palearctic, 7 are endemic to the Nearctic, and 8 are Holarctic sequences common to both zoogeographic zones. Differences in the sets of inversion sequences found on each continent, plus differing frequencies of Holarctic sequences, result in great overall divergence of karyotypes on the two continents. The karyotype of Nearctic C. plumosus differs from that of Palearctic populations primarily by the presence of a homozygous Nearctic sequence in arm A (n'plu A9), along with fixation (h'plu C2, h'plu E2, and h'plu F1), or high frequency (h'plu D2), of Holarctic sequences which are present but less frequent in the Palearctic. Although long continental isolation has led to great divergence of karyotypes on opposite sides of the Atlantic Ocean, all populations of C. plumosus show sufficient cytogenetic similarity to constitute a single Holarctic species.Key words: karyotype, inversion polymorphism, cytogenetic distances, Chironomus.
Satellite DNA in the antMessor structor(Hymenoptera, Formicidae)
Authors: Lorite P , García MF , Palomeque T
Published: April 2011

This paper is the first record of the satellite DNA of Formicidae. The satellite DNA of the ant Messor structor is organized in a tandem repeat of monomers of 79 bp. Like satellite DNAs of other insects, it is AT rich and presents direct and inverted internal repeats. Restriction analysis of the total DNA with methylation-sensitive enzymes strongly suggests that this DNA is undermethylated. The presence of this repetitive DNA in other species of the genus Messor is also tested. Key words: Formicidae, methylation, nucleotide DNA composition, satellite DNA.
RFLP mapping of a gene for hairy leaf sheath using a recombinant line from Hordeum vulgare L. ×Hordeum bulbosum L. cross
Authors: Korzun V , Malyshev S , Pickering R A , Börner A
Published: April 2011

A gene conditioning hairy leaf sheath character, which was derived from Hordeum bulbosum and designated Hsb, was mapped using a cross between Hordeum vulgare and a H. vulgare/H. bulbosum recombinant line. The Hsb locus was tagged relative to eight RFLP markers detecting three loci on the distal part of chromosome 4HL. The map position suggests that Hsb of H. bulbosum is homoeologous to the gene Hp1 of rye (Secale cereale), which pleiotropically governs the traits hairy leaf sheath and hairy peduncle. It is proposed that the recombination break point between H. vulgare and H. bulbosum chromosomes occured at a position homoeologous compared with the 4L/5L translocation in Triticeae genomes, and may reflect a hot spot for chromosome breakage.Key words: Hordeum vulgare, Hordeum bulbosum, comparative mapping, hairy leaf sheath, RFLP.
Genome plasticity during the acquisition of embryogenic competence
Authors: Geri Chiara , Turrini Alessandra , Giorgetti Lucia , Nicoletti Elisa , Ronchi Vittoria Nuti
Published: April 2011

Hypocotyl explants from carrot and other species experience concomitant segregation events and differentiation of homeotic structures during the first 20 days of culture on 2,4-dichlorophenoxyacetic acid (2,4-D). In addition to these cyto-morphological changes, significant amounts of nuclear DNA are lost, the molecular details of which we investigate in this paper. We have developed a slot-blot analysis assay to study the DNA content of a series of carrot samples; besides the leaves, this survey ranged over different culture timepoints: hypocotyls, cell lines, and somatic embryo stages. We carried on to study the relationship between this DNA loss and sequence complexity modulation. Results from probing sequences that correspond to different degrees of complexity, such as medium repetitive and unique sequences as well as sequences belonging to both classes (ribosomal cistrons, ubiquitin, actin, and chalcone synthase), consistently manifested a reduction in DNA levels during the acquisition of embryogenic competence. In some cases, the cultured cells would contain only 10% of the gene copies observed in the reference tissues. Modulation trends also showed that DNA levels of most sequences recover at the torpedo-plantlet stage, which again correlates DNA modulation and the acquisition of embryogenic competence. These results suggest that similar DNA variations may occur in plants in vivo during meiosis, possibly so that meiotic division may be properly completed.Key words: Daucus carota L., DNA reduction, somatic embryogenesis, totipotency, commitment.
Random amplified polymorphic DNA analysis, genome size, and genomic in situ hybridization of triploid viviparous onions
Authors: Puizina Jasna , Javornik Branka , Bohanec Borut , Schweizer Dieter , Maluszynska Jolanta , Pape Drazena
Published: April 2011

Triploid viviparous onions (Allium cepa L. var. viviparum Metzg. (ALEF.), auct.), (2n = 3x = 24), are known in some countries only as a rare relic crop, while in other parts of the world they are still traditionally or even commercially cultivated. Results indicating an identical random amplified polymorphic DNA (RAPD) banding pattern and the same DNA content (2C = 43.4 pg) establish the high genetic similarity and the unique origin of the Croatian clone Ljutika and the Indian clone Pran. In order to determine the parental Allium species of these natural triploid hybrids, genomic fluorescent in situ hybridization (GISH) was applied. Biotinylated genomic DNAs from six diploid Allium species (A. cepa L., A. fistulosum L., A. roylei Stearn, A. vavilovii M. Pop. et Vved., A. galanthum Kar. et Kir., A. oschaninii O. Fedtsch.) were used as probes in this study. While probes obtained from genomic DNA of A. cepa, A. vavilovii, and A. roylei hybridized to somatic chromosomes of Ljutika probes from A. fistulosum, A. galanthum, and A. oschaninii did not. The DNA probes of A. cepa and A. roylei each completely or predominantly labelled one genome (eight chromosomes). A few chromosomes, the markers of the triploid karyotype, were not completely labelled by any probe applied. Our GISH results indicate that triploid viviparous onions might possess a complex triparental genome organization.Key words: triploid viviparous onions, Allium cepa, Allium roylei, genomic in situ hybridization, genome size, random amplified polymorphic DNA (RAPD).
Microsatellites in the silkworm,Bombyx mori: Abundance, polymorphism, and strain characterization
Authors: Reddy K Damodar , Abraham E G , Nagaraju J
Published: April 2011

We have isolated and characterized microsatellites (simple sequence repeat (SSR) loci) from the silkworm genome. The screening of a partial genomic library by the conventional hybridization method led to the isolation of 28 microsatellites harbouring clones. The abundance of (CA)nrepeats in the silkworm genome was akin to those reported in the other organisms such as honey bee, pig, and human, but the (CT)nrepeat motif is less common compared to bumble bee and honey bee genomes. Detailed analysis of 13 diverse silkworm strains with a representative of 15 microsatellite loci revealed a number of alleles ranging from 3 to 17 with heterozygosity values of 0.66-0.90. Along with strain-specific microsatellite markers, diapause and non-diapause strain-specific alleles were also identified. The repeat length did not show any relationship with the degree of polymorphism in the present study. The co-dominant inheritance of microsatellite markers was demonstrated in F1offspring. A list of primer sequences that tag each locus is provided. The availability of microsatellite markers can be expected to enhance the power and resolution of genome analysis in silkworm.Key words: microsatellites, simple sequence repeats, polymorphisms, silkworm strains, Bombyx mori.
Cytological characterization of potato -Solanumetuberosumsomatic hybrids and their backcross progenies by genomic in situ hybridization
Authors: Dong F , Novy R G , Helgeson J P , Jiang J
Published: April 2011

Four somatic hybrids derived from a diploid wild species Solanum etuberosum and a diploid tuber-bearing Solanum clone 463-4, together with five BC1and three BC2plants, were analyzed by genomic in situ hybridization (GISH). None of the four somatic hybrids had the expected chromosome constitutions, i.e., 24 chromosomes from each fusion parent. Either one chromosome from S. etuberosum or one from the potato parent 463-4 was lost in the hybrids. Three BC1plants had exactly one set of S. etuberosum chromosomes. The other two BC1plants either had one extra or one fewer S. etuberosum chromosome, possibly because their somatic hybrid parents had an extra or had lost one S. etuberosum chromosome. The presence of one set, or close to one set, of S. etuberosum chromosomes in all BC1plants suggests a preferential pairing and segregation of the S. etuberosum chromosomes in the somatic hybrids. Two of the three BC2plants had 52 chromosomes, deviating significantly from the expected chromosome number of 48. These results suggest poor pairing between S. etuberosum and S. tuberosum chromosomes in the BC1plants. The present study demonstrates the importance of combining GISH and DNA marker analysis for a thorough characterization of potato germplasm containing chromosomes from different species.Key words: potato germplasm, Solanum etuberosum, molecular cytogenetics.
Molecular aids for integration of alien chromatin through wide crosses
Authors: Fedak G
Published: April 2011

Wide crosses in wheat have now been performed for over 100 years. In that time, approximately 100 genes have been transferred for numerous traits, including biotic and abiotic stresses and value-added traits. Resistance genes from alien sources do become defeated with time, so the search for additional variability must continue. Recent screening of alien species has identified accessions with multiple pest resistance plus combinations of pest resistance and value-added traits. The majority of existing induced recombinants are of a noncompensating type with considerable linkage drag, so sequential useage of Ph mutants is recommended to produce smaller interstitial recombinants. Molecular methods, including GISH, RAPD, RFLP, AFLP, and microsatellites, are being widely used to identify integrated alien chromosomes, chromosome segments, and genes.Key words: Triticum aestivium, molecular markers, disease resistance, gene introgression, interspecific hybrids.
Molecular changes atRrnloci in barley (Hordeum vulgareL.) hybrids withH. bulbosum(L.)
Authors: Kumar P Kranthi , Subrahmanyam N C
Published: April 2011

Southern blots of restriction fragments of genomic DNAs from Hordeum vulgare (L.), H. bulbosum (L.), and interspecific hybrids and their derivatives were hybridized with rDNA probe to identify locus-specific modifications at Rrn loci. H. bulbosum rDNA revealed a single EcoRV site per repeat compared with two sites in H. vulgare rDNA repeats. H. bulbosum accessions possessed at least two rDNA repeat lengths, indicating heterozygosity at the Rrn locus. Hybrids possessed both H. vulgare and H. bulbosum rDNA repeats. Two of the hybrid derivatives possessed bulbosum-specific Sau3AI and HaeIII rDNA fragments, while amphiploid and doubled haploid derivatives lacked H. bulbosum rDNA repeat units and (or) fragments. Two hybrid derivatives, one amphiploid and a doubled haploid derived from the same parental combination, lacked the vulgare Rrn2-specific 9.0-kb rDNA repeat. This is the first conclusive evidence for the elimination of vulgare genetic material in vulgare-bulbosum hybrids. The ratios of 9.0- to 9.9-kb vulgare repeats and H. vulgare to H. bulbosum rDNA repeats indicate partial loss of the vulgare-specific 9.0-kb rDNA repeat among the hybrids. Differences in MboI and Sau3AI fragments and the ratios of 9.0 to 9.9 kb vulgare rDNA repeats revealed differential methylation at Rrn1and Rrn2loci. Hybrids and derivatives showed differential distribution of methylation of EcoRI, BglII, and SacI sites at the Rrn1locus. Two of the hybrid derivatives exhibited extensive CpG-biased methylation. Data presented here are indicative of the differences in the onset of events triggered by the interaction of the component genomes and enabled detection of differential methylation among Rrn loci, loss of H. vulgare genetic material, and development of doubled haploids with the Rrn1locus.Key words: DNA methylation, elimination, Hordeum vulgare, H. bulbosum, Rrn loci.
Distribution of TGG repeat-related sequences in 'Trovita' orange (Citrus sinensis Osbeck) chromosomes
Authors: Matsuyama Tomoki , Akihama Tomoya , Ito Yuji , Omura Mitsuo , Fukui Kiichi
Published: April 2011

The clone pAS"C" is a sequence related to M13 phage minisatellite sequences isolated from bovine DNA. It contains TGG repeats, and related sequences are abundant in the Citrus genome. Fluorescent in situ hybridization (FISH) signals detected using this clone as a probe showed that the TGG repeat-related sequences are found on all the Citrus chromosomes, but are not found in Citrus-specific CMA+/DAPI- heterochromatic regions located at the extreme ends of each chromosome. These data suggest that the TGG-repeated sequences are evolutionarily conserved and that the CMA+/DAPI- heterochromatic regions were added to the chromosome ends at a recent stage in Citrus evolution.Key words: Citrus, minisatellite, microsatellite, SSRs, FISH.
Variations in the maizeActransposase transcript level and theDsexcision frequency in transgenic wheat callus lines
Authors: Takumi Shigeo , Murai Koji , Mori Naoki , Nakamura Chiharu
Published: April 2011

To investigate the excision of a maize transposable element in wheat cells, plasmid DNAs containing a Dissociation (Ds) element located between a rice actin 1 gene promoter and a beta-glucuronidase (GUS) gene (gus) were introduced into wheat callus lines by microprojectile bombardment, and transient GUS expression was assayed. The gus-expressing cells after Ds excision were detected only when the Activator (Ac) transposase gene was co-transformed. To further examine a relationship between the amount of Ac mRNA and the Ds excision frequency, the Ds-containing plasmids were introduced into 15 independent transgenic callus lines transformed with the Ac transposase gene. Ten lines expressed the Ac transposase gene under the control of either the cauliflower mosaic virus 35S promoter or the Ac native promoter. The gus gene expression that indicated the Ds excision was observed only in the transgenic callus lines stably expressing the Ac transposase gene. The number of blue spots reflecting the frequency of Ds excision was variable among them. Northern-blot analysis also showed a large variability in the amount of Ac transposase transcripts among the lines. It was however noted that the excision frequency was decreased at a high level of the Ac transposase transcripts, supporting the hypothesis that Ds excision is inhibited above a certain level of the Ac transposase as observed in maize and transgenic tobacco.Key words: transposon, Ds excision, Ac transposase transcript level, transgenic callus, wheat.