bluuebunny/crossref_metadata_2025 huggingface dataset:
Standard karyotype of Triticum longissimum and its cytogenetic relationship with T. aestivum
Authors: Friebe Bernd , Tuleen Neal , Jiang Jiming , Gill Bikram S.
Published: May 2008

C-banding polymorphism was analyzed in 17 accessions of Triticum longissimum from Israel and Jordan, and a generalized idiogram of this species was established. C-banding analysis was further used to identify two sets of disomic T. aestivum – T. longissimum chromosome addition lines and 13 ditelosomic addition lines and one monotelosomic (6S1L) addition line. C-banding was also used to identify T. aestivum – T. longissimum chromosome substitution and translocation lines. Two major nucleolus organizing regions (NORs) on 5S1 and 6S1 and one minor NOR on 1S1 were detected by in situ hybridization using a 18S–26S rDNA probe. Sporophytic and gametophytic compensation tests were used to determine the homoeologous relationships of T. longissimum chromosomes. The T. longissimum chromosomes compensate rather well and fertility was restored even in substitution lines involving wheat chromosomes 2A, 4B, and 6B that contain major fertility genes. Except for the deleterious gametocidal genes, T. longissimum can be considered as a suitable donor of useful genes for wheat improvement.Key words: Triticum aestivum, Triticum longissimum, homoeology, C-banding, in situ hybridization.
RFLP linkage map and genome analysis of Saccharum spontaneum
Authors: Silva Jorge A. G. da , Sorrells Mark E. , Burnquist William L , Tanksley Steven D.
Published: May 2008

An RFLP linkage map of the wild sugarcane species Saccharum spontaneum L. (2n = 8x = 40–128) was constructed, comprising 216 loci, detected by 116 DNA probes, and distributed over 44 linkage groups. At a density of at least one marker every 25-cM interval, the coverage of the genome was estimated as 86%. For the generation of RFLP markers, probes were surveyed from seven DNA libraries: three sugarcane cDNA, one oat cDNA, one rice cDNA, and one barley cDNA, as well as one sugarcane genomic. Sixty-two maize genomic clones that were previously mapped on maize were used to initiate a comparative map between the sugarcane, sorghum, and maize genomes. Based on the RFLP segregation data, we conclude that this species is an autopolyploid, with an estimated genome size of 2107 cM.Key words: sugarcane, polyploid, RFLP, map, genome.
Nuclear gametophytic genes from chromosome arm 1RS improve regeneration of wheat microspore-derived embryos
Authors: Henry Y. , Bernard S. , Bernard M. , Gay G. , Marcotte J.-L. , Buyser J. De
Published: May 2008

The effect of the 1RS chromosome arm from rye on plant regeneration from microspore-derived embryos was studied using anther culture technology with genotypes carrying the 1BL–1RS translocated chromosomes, the normal wheat chromosome 1BL–1BS, and ditelosomic lines DT 1BS and DT 1BL. A significant difference was observed in microspore-derived green plants between chromosome structure concerned with 1RS and 1BS arms. An analysis of the inheritance of the 1B–1R translocation was performed on the basis of the frequency of male gametes 1BL–1RS in the microspore-derived green plants and that of the 1B–1R translocation inherited through the pollen or the egg cell from structurally heterozygous hybrids 1BL–1BS/1BL–1RS. Both the normal 1B and the translocated 1BL–1RS chromosomes were sexually transmitted through the pollen grains with the same frequency. The 1BL–1RS chromosome is only transmitted through 45% of the egg cells. On the contrary, two-thirds of the microspore-derived green plants regenerated from the anther culture experiments possess the translocated chromosome. The involvement of the rye chromosome arm 1RS from 'Aurora' on regeneration capacity of the microspore-derived embryos has been proposed through the effect of a "gametophytic gene."Key words: anther culture, 1RS arm, gametophytic gene.
Reconstruction in wheat of complete chromosomes 1B and 1R from the 1RS.1BL translocation of 'Kavkaz' origin
Authors: Lukaszewski Adam J.
Published: May 2008

Translocation 1RS.1BL originally from the 'Aurora' and 'Kavkaz' wheats has spread to bread wheats all over the world. It offers several resistance genes and appears to significantly increase yields. For future study of the arm location of the yield-increasing factors, complete chromosomes 1B and 1R were reconstructed from the 1RS.1BL translocation. This was accomplished by centric misdivision and fusion in double monosomies 20 II + 1RS.1BL I + 1BS.1RL I. The frequency of misdivision and misdivision–fusion of the two unpaired chromosomes was 23.1%, which was much higher than expected but comparable with that observed in other stocks grown under similar conditions. Transmission of the reconstructed chromosomes to progeny was normal. In addition to all possible misdivision and misdivision–fusion products, two chromosomes of ambiguous origin were recovered: chromosome 1B with a proximal insert of about 40% of 1RS and chromosome 1R with a proximal insert of about 30% of 1BS. The study demonstrates that centric translocations can misdivide and fuse again to produce stable chromosomes with new arm combinations.Key words: wheat, 1RS.1BL translocation, misdivision.
A molecular cytogenetic comparison between Rhynchosciara americana and Rhynchosciara hollaenderi (Diptera: Sciaridae)
Authors: Stocker Ann Jacob , Gorab Eduardo , Amabis J. M. , Lara F. J. S.
Published: May 2008

The polytene chromosomes of Rhynchosciara americana and R. hollaenderi, a pair of sibling species in the americana-like group of Rhynchosciara, were compared using a number of techniques, including in situ hybridization. With classical cytological techniques, the only differences observed were in the morphology of centromeric and telomeric heterochromatin, in the size of a DNA and RNA puff, and in the presence of an inversion polymorphism in R. hollaenderi. However, after in situ hybridization with rDNA and poly-r(A) probes, differences between the two species appeared at a number of sites. Differences in poly-r(A) sites were especially informative in establishing phylogenetic relationships between these two species and a third species currently being examined from this group. Chromosomal evolution between these species appears to have occurred mainly through differential amplification and transposition of repetitive sequence DNA, of which dA:dT tracts are an important component. The R. hollaenderi karyotype is tentatively considered more ancestral than that of R. americana because it has features present in the third Rhynchosciara species. Explanations for the monomorphisms observed in Rhynchosciara species and mechanisms of speciation in the group are considered within the context of the species' complex behavior.Key words: Rhynchosciara, chromosome homology, in situ hybridization, phylogeny, evolution.
Evolution of histone gene loci in chironomid midges
Authors: Hankeln Thomas , Keyl Hans-Günther , Ross Ralf , Schmidt Erwin R.
Published: May 2008

In the present study we have localized the histone genes in the chromosomes of 16 different Chironomus species as well as in Prodiamesa olivacea, Glyptotendipes barbipes, and Acricotopus lucidus. In the genus of Chironomus we find four, five, or six different "major" chromosomal loci hybridizing with a histone gene cluster probe isolated from the genome of Chironomus thummi. These major histone gene loci probably contain clustered histone gene repeating units ("clustered" loci). They are located on one and the same chromosome arm in all but one of the species investigated. This shows that the histone gene clusters are rather conservative in their location over a long period of evolution. The comparison of the histone loci pattern from the chromosomes of the different chironomid species shows that there is good agreement with previously established chromosome maps and phylogenetic studies based on the chromosomal banding pattern. Stringent in situ hybridization with various histone gene containing clones suggest that the "clustered" histone gene loci are organized in a locus-specific way. In addition to the linked "clustered" histone gene loci, we found an isolated histone gene group ("orphon") present on chromosome IV in most Chironomus species. This gene group might be organized differently from the histone gene repeating unit described previously.Key words: histone genes, Chironomus, in situ hybridization, transposition, orphon.
Mapping maize microsatellites and polymerase chain reaction confirmation of the targeted repeats using a CT primer
Authors: Senior M. Lynn , Heun Manfred
Published: May 2008

Microsatellites, also called simple sequence repeats (SSRs), have yielded an important class of DNA markers most notable for mapping mammalian genomes. To study the occurrence of microsatellites and their inheritance in maize, a search was made of 280 maize GenBank® sequences. Six SSRs were chosen and unique flanking primers were designed for polymerase chain reaction (PCR) amplification. Eight different maize inbreds were studied with these six primer pairs and a mean of 3.5 polymorphic patterns occurred within the expected size range. For five of these putative microsatellites, the segregation in a maize restriction fragment length polymorphism mapping population was analyzed. Four of the microsatellites cosegregated with the Adh1, Gpc1, Pdk1, and Tpi genes from which the primer sequences were derived. The fifth primer pair (MZEGPA1) showed segregating polymorphisms, but the products were larger than expected. To verify the existence of the original SSRs in the segregating PCR products, a CT primer, containing a CT SSR and an arbitrary leader sequence, was used to reamplify these products. The four microsatellites that cosegregated with the original gene were reamplified as anticipated, whereas a suspicious 230-bp product obtained when using the MZEGPA1 primers could not be reamplified. Based on these results it is concluded that microsatellites can be a valuable tool for maize mapping.Key words: maize, microsatellites, simple sequence repeats, genome mapping.
A supernumerary chromosome segment in Locusta migratoria
Authors: Pardo M. C. , Viseras E. , Cabrero J. , Camacho J. P. M.
Published: May 2008

A single female of Locusta migratoria was found to be heterozygous for a supernumerary heterochromatic segment distally located on the M6 autosome close to its nucleolus organiser region (NOR). Reactions to several chromosome banding techniques revealed its heterochromatic nature and its composition of GC-rich DNA sequences and likewise the NORs in this species. This suggests an origin for the extra segment by amplification of GC-rich DNA sequences contained in the distal NOR of the M6 chromosome, which is reinforced by the observation that the NOR of segmented M6 chromosomes produced the larger nucleolus in embryo prophase cells, such as would be expected from the presence of rRNA genes in the extra segment. No accumulation mechanism was detected in this female after analyzing the 213 embryo offspring produced, but an increase in the number of nucleoli per interphase nucleus was noted in heterozygous embryos in respect to standard homozygous ones.Key words: Locusta migratoria, supernumerary segments, nucleolar organizing regions, heterochromatin.
Fluorescence in situ hybridization of bovine Alu-like sequences to bovine and ovine chromosomes
Authors: Rajcan-Separovic E. , Sabour M. P.
Published: May 2008

Fluorescence in situ hybridization procedures have been applied to study the distribution of Alu-like sequences on bovine and ovine chromosomes. Unlike in man and mouse, where the Alu sequences produced discrete R-like bands, a more diffuse distribution of Alu-like sequences was observed on both bovine and ovine chromosomes. Under the conditions used, banding patterns useful for chromosome identification were not detected.Key words: bovine Alu-like repetitive sequences, bovine and ovine chromosomes, fluorescence in situ hybridization.
Chromosome pairing and potential for intergeneric recombination in some hypotetraploid somatic hybrids of Lycopersicon esculentum (+) Solanum tuberosum
Authors: Jong J. H. de , Wolters A. M. A. , Kok J. M. , Verhaar H. , Eden J. van
Published: May 2008

Three somatic hybrids resulting from protoplast fusions of a diploid kanamycin-resistant line of tomato (Lycopersicon esculentum) and a dihaploid hygromycin-resistant transformant of a monohaploid potato (Solanum tuberosum) line were used for a cytogenetic study on chromosome pairing and meiotic recombination. Chromosome counts in root-tip meristem cells revealed two hypotetraploids with chromosome complements of 2n = 46 and one with 2n = 47. Electron microscope analyses of synaptonemal complex spreads of hypotonically burst protoplasts at mid prophase I showed abundant exchanges of pairing partners in multivalents involving as many as eight chromosomes. In the cells at late pachytene recombination nodules were found in multivalents on both sides of pairing partner exchanges, indicating recombination at both homologous and homoeologous sites. Light microscope observations of pollen mother cells at late diakinesis and metaphase I also revealed multivalents, though their occurrence in low frequencies betrays the reduction of multivalent number and complexity. Precocious separation of half bivalents at metaphase I and lagging of univalents at anaphase I were observed frequently. Bridges, which may result from an apparent inversion loop found in the synaptonemal complexes of a mid prophase I nucleus, were also quite common at anaphase I, though the expected accompanying fragments could be detected in only a few cells. Most striking were the high frequencies of first division restitution in preparations at metaphase II/anaphase II, giving rise to unreduced gametes. In spite of the expected high numbers of balanced haploid and diploid gametes, male fertility, as revealed by pollen staining, was found to be negligible.Key words: synaptonemal complex, recombination, chromosome pairing, somatic hybrid, Lycopersicon esculentum (+) Solanum tuberosum.
The mitochondrial genome of Anopheles quadrimaculatus species A: complete nucleotide sequence and gene organization
Authors: Mitchell Sharon E. , Cockburn Andrew F. , Seawright Jack A.
Published: May 2008

The complete sequence (15 455 bp) of the mitochondrial DNA of the mosquito Anopheles quadrimaculatus species A is reported. This genome is compact and very A + T rich (77.4% A + T). It contains genes for 2 ribosomal RNAs (rRNAs), 22 transfer RNAs (tRNAs), and 13 subunits of the mitochondrial inner membrane respiratory complexes. The gene arrangement is the same as in Drosophila yakuba, except that the positions of two contiguous tRNAs are reversed and a third tRNA is transcribed from the complementary strand. Protein-coding genes, rRNAs, and most tRNAs were similar to D. yakuba. Two tRNAs had nonstandard secondary structures comparable with those of nematode mitochondrial tRNAs. The very small putative control region (625 bp) contains no sequence motifs similar to those used in vertebrates and other insects for initiation of transcription and replication.Key words: mitochondrial DNA, Anopheles quadrimaculatus.
Molecular mapping of genes determining height, time to heading, and growth habit in barley (Hordeum vulgare)
Authors: Barua U. M. , Chalmers K. J. , Thomas W. T. B. , Hackett C. A. , Lea V. , Jack P. , Forster B. P. , Waugh R. , Powell W.
Published: May 2008

A combination of random amplified polymorphic DNA (RAPD) and restriction fragment length polymorphism (RFLP) markers has been used to locate genes controlling important developmental characters in barley. The denso dwarfing gene has been mapped to the long arm of chromosome 3H. Stepwise multiple regression was also used to identify another region of the barley genome (on chromosome 7H), which contributed to variation in height. The denso locus was shown to be associated with delaying time to heading. A protein (WSP2) and an RAPD marker on barley chromosomes 5H and 6H, respectively, were also associated with time to heading. These results are discussed in relation to the genetic analysis of developmentally important traits and the development of dwarfing genes in barley breeding programs.Key words: RAPDs, RFLPs, denso dwarfing gene, barley, doubled haploids, heading date.
Interspecific hybrids between a transgenic rapeseed (Brassica napus) and related species: cytogenetical characterization and detection of the transgene
Authors: Kerlan M. C. , Chevre A. M. , Eber F.
Published: May 2008

In interspecific hybrids produced between a transgenic rapeseed, an allotetraploid species, resistant to herbicide, phosphinotricin, and five diploid related species, the risk for gene introgression in weed genomes was explored through cytogenetic and bar gene characterizations. Among the 75 hybrids studied, most had the expected triploid structure, with the exception of B. napus – B. oleracea amphidiploid plants and one B. napus – S. arvensis amphidiploid plant. In triploid hybrid plants, the reciprocal hybrids did not exhibit any difference in their meiotic behavior. The comparison of the percentage of chromosome pairing in the hybrids with that of haploid rapeseed permit to conclude that allosyndesis between AC genomes and related species genomes took place. This possibility of recombination was confirmed by the presence of multivalent associations in all the interspecific hybrids. Nevertheless, in B. napus – B. adpressa hybrids a control of chromosome pairing seemed to exist. The possibility of amphidiploid plant production directly obtained in the F1 generation increased the risk of gene dispersal. The B. napus – B. oleracea amphidiploid plant presented a meiotic behavior more regular than that of the B. napus – S. arvensis amphidiploid plant. Concerning the herbicide bar gene characterization, the presence of the gene detected by DNA amplification was correlated with herbicide resistance, except for two plants. Different hypotheses were proposed to explain these results. A classification of the diploid species was established regarding their gene dispersal risk based on the rate of allosyndesis between chromosomes of AC genomes of rapeseed and the genomes of the related species.Key words: Brassicaceae, transgenic rapeseed, risk assessment, interspecific hybrids, chromosome pairing, bar gene characterization.
Quantitative analysis of the variability of nucleolar organizer regions in Salmo trutta
Authors: Martínez P. , Viñas A. , Bouza C. , Castro J. , Sánchez L.
Published: May 2008

A quantitative analysis combined with Ag staining was carried out to study the size variation of the main nucleolar organizer region (NOR) bearing chromosome pair 11 of Salmo trutta. A standardized NOR size measurement was developed by comparing the length of the short arm (NOR-bearing region) to the total chromosome length. Statistical procedures support arguments for the existence of a large and structural polymorphism within this species for this chromosome region. A minimum of five different chromosome classes were identified, which account for the total variation found. Size variation among classes was due both to changes in the number of NOR clusters as well as to the amount of rDNA genes within each cluster. NOR size values were normally distributed in the sample analyzed.Key words: nucleolar organizer region, size polymorphism, brown trout.
Evidence for mobilization of hobo transposons in a P-element mutagenesis screen
Authors: Locke J. , Hanna S. , Kong D.
Published: May 2008

In Drosophila melanogaster, mutations in Su(var) and En(var) loci either suppress or enhance position effect variegation, respectively. Towards the cloning of these genes we have induced, recovered, and characterized a series of Su(var) mutations located on the third chromosome. These mutations were recovered from a P-element mutagenesis scheme in which the third chromosome P[ry+ Δ2–3](99B) element would provide transposase in trans to mobilize a single nonautonomous P transposon, P[pUCHSNeo](9C), located on the X chromosome. Although this cross scheme induces mobilization of the X-chromosome P transposons and its subsequent reinsertion onto the autosomes, none of the Su(var) mutations recovered could be associated with P-transposon insertions. Further investigation of these mutations by in situ hybridization showed that another mobile element that can be mobilized in hybrids, hobo, was associated with these mutations. We conclude that the mobilization and reinsertion of the hobo elements, through an inadvertent hybrid HE dysgenic cross, is most likely responsible for the Su(var) mutations recovered from this P-element mutagenesis. The association of hobo elements with this Su(var) locus will facilitate its cloning and offers the possibility of hobo transposon tagging other Su(var) loci.Key words: Drosophila, mobile elements, P element, hobo element, position effect variegation, Su(var).
Heritable effects of 5-azacytidine treatments on the growth and development of flax (Linum usitatissimum) genotrophs and genotypes
Authors: Fieldes M. A.
Published: May 2008

Seed of flax (Linum usitatissimum) were treated for short durations with 5-azacytidine and the direct and heritable effects of the treatments on plant growth and development in general and, more specifically, on the contrasting phenotypes of Durrant's large and small genotrophs were examined. 5-Azacytidine induced a reduction in the height of the plants grown from treated seed. Twenty-two percent of the first generation progeny of these plants also had short phenotypes and, in most cases, the short phenotype was stably and uniformly inherited by the second generation progeny of the short, first generation plants. Treatment also induced a marked decrease in the flowering age in a few of the first generation plants that was also transmitted to their second generation progenies. The effects seen in the progeny generations suggest that most, if not all, of the heritable changes induced by the treatment are epigenetic. Several differences were seen between the large and small genotrophs, which indicate that the genome of the small genotroph is less susceptible, than the genome of the large genotroph, to 5-azacytidine induced heritable alterations.Key words: flax genotrophs, 5-azacytidine, height, flowering.
A cytogenetic analysis of the Simulium ochraceum species complex (Diptera: Simuliidae) in Central America
Authors: Hirai Hirohisa , Procunier William S. , Ochoa J. Onofre , Uemoto K.
Published: May 2008

A cytobiotaxonomic study of the medically important insect vector Simulium ochraceum s.l. revealed two sibling species and one cytotype from various endemic and nonendemic zones of human onchocerciasis in Guatemala and Mexico. Polytene chromosome maps and idiograms as well as notes on the biology of the three taxa designated S. ochraceum A, S. ochraceum B, and S. ochraceum C within the subgenus Psilopelmia are presented. All three taxa exhibit distinct sex chromosomes and taxon-specific suites of autosomal inversion polymorphisms. Simulium ochraceum C differs from both S. ochraceum A and S. ochraceum B by five interspecific inversions designated IIS-7,8 and IIIL-12, 13 + 14, 15. The three taxa exhibit niche and biting preferences, with S. ochraceum A being highly anthropophilic. Analysis of autosomal inversion polymorphism profiles indicates S. ochraceum A has long-range dispersal capability. Our results are consistent with the general findings that in the Simuliidae, sibling speciation may be suspected wherever a morphospecies occupies different niches in a stream continuum. We find for the first time an apparent partitioning of taxa by altitude. Simulium ochraceum A may be a primary vector of human onchocerciasis in Guatemala, as its vertical distribution is coincident with that of the highest areas of nodule prevalence in the human population. A genotypic component of variation in vectorial capacity of S. ochraceum A populations seems to occur, since the Y4 chromosome and its X chromosome counterpart are associated with hyperendemic areas of human onchocerciasis. Our observation that a supernumerary band, 37B1Hb, is associated with sex determination in two of the taxa may be of significance for the elucidation of the molecular basis of sex determination and possible resolution of issues pertinent to the general model of sympatric speciation in the Simuliidae.Key words: Simulium ochraceum complex, cytobiotaxonomy, vector biology, sex chromosome evolution, human onchocerciasis.
Linkage mapping in diploid alfalfa (Medicago sativa)
Authors: Echt C. S. , Kidwell K. K. , Knapp S. J. , Osborn T. C. , McCoy T. J.
Published: May 2008

A genome map of cultivated alfalfa was constructed using segregating restriction fragment length polymorphisms (RFLPs) and random amplified polymorphic DNAs (RAPDs) in a diploid backcross population generated from noninbred parents. Among the 153 loci scored in 87 progeny, four segregation ratios were observed for codominant and dominant markers: 1:1, 1:2:1, 1:1:1:1, and 3:1. Deviations from expected Mendelian ratios (p < 0.05) were observed for 34% of the loci studied. A genome map was assembled from two separate linkage maps, each constructed from a subset of the segregation data. One linkage map was constructed from 46 RFLP and 40 RAPD markers segregating 1:1 from the F1 parent of the backcross and the other linkage map was constructed from 33 RFLP and 28 RAPD markers segregating 1:1 from the recurrent parent. Sixteen loci with alleles segregating 1:1 from both parents were used as locus bridges to align individual linkage groups between the two maps. The combined use of RFLPs and RAPDs was an effective method for developing an alfalfa genome map.Key words: genome mapping, RAPD, RFLP, locus bridges.
Isolation of a new species-specific repetitive sequence from Thinopyrum elongatum and its use in the studies of alien translocations
Authors: Bournival B. , Obanni M. , Abad A. , Ohm H. , Mackenzie S.
Published: May 2008

A new repetitive sequence that is extremely abundant and well dispersed in the Thinopyrum elongatum genome but present in low-copy number in wheat (Triticum aestivum L.) has been isolated. This repeat and a Th. elongatum repeat isolated in another laboratory were used to identify cosmid genomic clones containing the repeats and, thus, putatively located on a Th. elongatum/T. aestivum translocation arm. Most of the selected cosmids contained single-or low-copy sequences, making them potentially useful in mapping studies. The repeats were used in deletion mapping to deduce gene order of three genes located on the Th. elongatum translocation arm. In situ hybridization studies suggested that this newly identified Th. elongatum repeat is well dispersed throughout the Thinopyrum genome but present at only one location in wheat. This raises some interesting questions about the role of such repetitive elements in the evolution of grass species.Key words: species-specific repeats, wheat, wheatgrass, Agropyron elongatum, in situ hybridization.
Physical mapping of 5S rDNA loci by direct-cloned biotinylated probes in barley chromosomes
Authors: Fukui K. , Kamisugi Y. , Sakai F.
Published: May 2008

5S rDNA loci have been mapped on barley chromosomes by in situ hybridization using five reciprocal translocation lines. Two kinds of DNA probes covering either the 5S rDNA coding region or the 5S rDNA coding and flanking noncoding regions were used. They were prepared by direct cloning from interphase nuclei and simultaneous direct labeling in PCR. Four 5S rDNA loci were detected in a haploid genome by the 5S rDNA coding region, whereas in addition, the four or six 5S rDNA related sites, depending on the variety used, were revealed by the probe covering the flanking region. The four 5S rDNA loci revealed and mapped on the barley chromosomes: 2 (2I), 3 (3I), 1 (7I), and 4 (4I) were designated 5SRrn-I1, 5SRrn-I2, 5SRrn-I3 and 5SRrn-I4, respectively, in descending order of copy number of 5S rRNA genes.Key words: Hordeum vulgare, 5S rDNA, in situ hybridization, direct cloning, direct labeling.
Triose phosphate isomerase of Stellaria longipes (Caryophyllaceae)
Authors: Zhang Xing-Hai , Chinnappa C. C.
Published: May 2008

A cDNA encoding triose phosphate isomerase (TPI) of Stellaria longipes has been isolated and sequenced. The TPI of S. longipes exhibits high similarity to the TPIs from other species at both the nucleotide and amino acid levels. Southern blot analysis showed that the S. longipes genome contained multiple TPI-like nucleotide sequences and only a low degree of polymorphism was observed among genotypes of different habitats. The levels of TPI mRNA, detected by hybridization to the TPI cDNA, appeared similar between the genotypes. However, different genotypes showed variations in the total TPI activity, reflecting the possible ecological effect on the TPI gene expression. Northern blot hybridization to the cDNA also indicated a higher level of TPI mRNA in leaves than in roots, suggesting tissue-specific expression of TPI gene(s). Phylogenetic analysis of the TPI amino acid sequences from 16 taxa suggested that the TPI from S. longipes was more closely related to cytosolic TPIs from other plants than it was to TPIs from prokaryotes.Key words: triose phosphate isomerase, Stellaria longipes, genotype, ecotypes, molecular phylogeny.
A genomic clone of a type I cab gene encoding a light harvesting chlorophyll a/b binding protein of photosystem II identified from lodgepole pine
Authors: Barrett John W. , Beech Robin N. , Dancik Bruce P. , Strobeck Curt
Published: May 2008

A type I cab gene encoding chlorophyll a and b binding protein from lodgepole pine (Pinus contorta Dougl., var. latifolia (Engelm.)) has been isolated and sequenced. The gene encodes a proposed 40 amino acid transit peptide and a 234 amino acid mature CAB polypeptide. There is no evidence of an intron and examination of the type-specific amino acids confirm this to be a photosystem II type I cab gene. The coding region is highly conserved with a similar gene from Scots pine, the homology extending into the 5′ and 3′ untranslated regions. Sequence comparison of the 1-kb region upstream of the translation start codon from the lodgepole pine cab gene exhibited little similarity to identified regulatory regions in pea, tobacco, wheat, and Arabidopsis cab genes. The cab gene, which is 62% G + C rich, is surrounded by 70–75% A + T rich regions, which may confer some regulatory feature on its expression.Key words: chlorophyll a/b binding protein, gymnosperm, lodgepole pine, photosystem II type I cab gene.
Direct incorporation of fluorescein-12-dUTP to insect fixed chromosomes by random primed extension
Authors: Juan C. , Gosálvez J.
Published: May 2008

The use of an in situ random primed system allows the direct incorporation of fluorescein-12-dUTP into fixed insect chromosomes, resulting in a strong fluorescent labelling. While in an orthopteran species (Eyprepocnemis plorans) a relatively uniform labelling of meiotic and mitotic chromosomes is produced, in Tenebrio molitor (Coleoptera) only the chromosomal arms, but not the pericentromeric heterochromatic areas of mitotic chromosomes, show positive labelling by this method. This indicates that the organization of DNA in heterochromatin is distinct from that in the euchromatin in distantly related species, and in such a way that, in some species, the random hexanucleotides are prevented from annealing with the chromosomal denatured DNA or (and) that primer extension by Klenow enzyme is impeded.Key words: insect, chromosome, fluorescein-12-dUTP, in situ labelling.
Haldane's rule and heterogametic female and male sterility in the mouse
Authors: Biddle Fred G. , Eales Brenda A. , Dean Wendy L.
Published: May 2008

Failed genetic experiments or experiments designed for other purposes sometimes reveal novel genetic information. The interspecific cross between laboratory strain mice of the Mus musculus musculus/domesticus complex and the separate species M. spretus is known to produce fertile F1 females and sterile F1 males. Infertility of the interspecific F1 XY male is said to be an example of what has become known as Haldane's rule: "When in the F1 offspring of two different animal races one sex is absent, rare, or sterile, that sex is the heterozygous [heterogametic] sex." We attempted to use fertile single-X (or XO) female laboratory mice of the M. m. musculus/domesticus complex mated to M. spretus males to construct females with specific X chromosomes to study segregation distortion of X chromosome marker genes that we reported previously in crosses with the two species. We assumed that the interspecific F1 XO female would be fertile like the interspecific F1 XX female but, instead, we found that it is infertile. Haldane's rule is not specific to sex, but demonstration of this has required study of separate species pairs with heterogametic males or with heterogametic females. The fertile XO laboratory mouse is female, but it is also heterogametic, producing both X and nullo-X eggs. Infertility of both the interspecific and heterogametic F1 XO female and F1 XY male in the same cross between laboratory mice and M. spretus suggests that heterogamety is at the cause of the infertility. The most parsimonious interpretation is that there is an interaction between the single X and heterozygous or heterospecific autosomes that may affect the same fundamental step in both female and male meiosis in the interspecific F1 hybrid. This hypothesis is now testable in the mouse.Key words: interspecific crosses, mouse, Haldane's rule.
Interactions between the scs and Vi genes in alloplasmic durum wheat
Authors: Maan S. S.
Published: May 2008

Two nuclear genes, vitality (Vi) on an A- or B-genome chromosome and species cytoplasm specific (scs) on a 1DL telosome from Triticum aestivum L. or a telosome from Aegilops uniaristata Vis. (un telosome), improved compatibility between the nucleus of Triticum turgidum L. var. durum and the cytoplasm of Ae. longissima S. &M. or Ae. uniaristata. To study interactions between Vi and scs and to determine the chromosomal location of Vi, 29-chromosome fertile plants were crossed with 13 D-genome disomic-substitution (d-sub) lines [except 5D(5A)] of 'Langdon' durum. F1 and backcross progenies were examined for meiotic chromosome number and pairing, fertility, and plant vigor. In 11 crosses, Vi restored seed viability but produced double-monosomics (d-monos) with greatly reduced growth and vigor. In contrast, crosses involving 1D(1A) and 1D(1B) d-sub lines produced d-monos with normal vigor and anthesis but nonfunctional pollen. A backcross of 1D + 1A d-mono F1 and 1D(1A) d-sub lines produced 11 male steriles; 3 had 13 II + 1 II 1D + 1 I 1A, 2 had 13 II + 2 I, 1 had 13 II + 1 II 1D(1A), and 5 were not examined. Crosses of 1D + 1A d-mono F1 with control durum, lo durum (with 1DL), and un durum (with un telosome) lines produced 16 male-sterile d-monos and 14 fertiles with 14 II + 1 I 1D, showing that 15-chromosome female gametes transmitted monosomes 1A and 1D. However, BC2F1's from 1D + 1B d-mono × fertile line with un telosome included 20 male-sterile d-monos, 6 fertile triple monosomics (13 II + 1 I 1D + 1 I 1B + t I un telosome), and 1 fertile plant with a 1B/1D translocation. Unlike d-mono 1A + 1D, d-mono 1B + 1D did not transmit 15-chromosome female gametes with monosomes 1D and 1B. Additional backcrosses also indicated that homozygous scs caused male sterility in 1D(1A) and 1D(1B) d-subs and that the procedure used was not suitable for the chromosomal location of Vi.Key words: alien cytoplasm, nucleocytoplasmic interactions, 1B/1D translocation, aneuploidy, cytoplasmic male sterility.
Molecular tagging of genes for brown planthopper resistance and earliness introgressed from Oryza australiensis into cultivated rice, O. sativa
Authors: Ishii T. , Brar D. S. , Multani D. S. , Khush G. S.
Published: May 2008

Restriction fragment length polymorphism analysis was carried out to tag the alien genes for brown planthopper (BPH) resistance and earliness introgressed from wild species Oryza australiensis into cultivated rice, O. sativa L. One introgression line (IR65482-4-136-2-2), resistant to biotypes 1, 2, and 3 of BPH and early in flowering, was selected from BC2F4 of the cross between O. sativa (IR31917-45-3-2) and O. australiensis (accession 100882). Recurrent parent, O. australiensis, and introgression line were surveyed for RFLP using probes of chromosomes 10 and 12. Two probes, RG457 and CDO98, detected introgression from O. australiensis. Cosegregation between introgressed characters and molecular markers was studied in F2 derived from the cross between the introgression line and recurrent parent. The gene for BPH resistance is linked with RG457 of chromosome 12 at a distance of 3.68 ± 1.29 cM, and the gene for earliness is linked with CDO98 of chromosome 10 at a distance of 9.96 ± 3.28 cM. Such close linkage is useful in marker-based selection while transferring BPH resistance from introgression line into other elite breeding lines. Introgression at the molecular level indicates that the mechanism of alien gene transfer is probably genetic recombination through crossing over rather than substitution of whole or large segment of chromosomes of wild species.Key words: molecular tagging, alien gene introgression, rice, wild species, brown planthopper resistance.
A molecular approach to unraveling the genetics of sugarcane, a complex polyploid of the Andropogoneae tribe
Authors: D'Hont Angélique , Lu Yun-Hai , León Diego González de , Grivet Laurent , Feldmann Philippe , Lanaud Claire , Glaszmann Jean Christophe
Published: May 2008

Modern sugarcane varieties are complex aneuploids and typically have chromosome numbers in the 100–125 range with about 5–10% of them contributed by wild relatives, mainly Saccharum spontaneum, and the rest by S. officinarum. This particular genomic constitution was found favorable for mapping the S. spontaneum genome, using maize as a diploid reference for comparison. We conducted an analysis of 32 individuals derived from the selfing of variety SP 701006 using four isozymes and 53 maize probes which covered the whole maize genome. A total of 348 segregating bands were generated. Highly significant cosegregations enabled us to place 94 markers into 25 cosegregation groups. Eighteen of these groups involved S. spontaneum specific markers and might therefore mark S. spontaneum chromosomes in segregation. On the basis of probes in common, the 25 cosegregation groups could be assembled into eight tentative linkage groups, of which seven describe S. spontaneum chromosomes. A large degree of synteny between sugarcane and maize could be inferred, with a much lower rate of recombination in sugarcane.Key words: sugarcane, maize, RFLP, polyploid, genetic mapping.
Absence of the J genome in Leymus species (Poaceae: Triticeae): evidence from DNA hybridization and meiotic pairing
Authors: Wang Richard R.-C. , Jensen Kevin B.
Published: May 2008

To test the presence of a J genome in the type species of Leymus, L. arenarius, its total genomic DNA and that of tetraploids L. mollis, L. salinus ssp. salmonis, L. ambiguus, L. chinensis, L. secalinus, L. alaicus ssp. karataviensis, and L. innovatus were probed with the 277-bp insert of pLeUCD2, which can hybridize with the J, S, and P but not with the N, R, V, Q, I, T, and ABD genomes. The DNA probe hybridized with PalI- or TaqI-digested total DNAs from Thinopyrum elongatum (JeJe diploid) and T. elongatum × Psathyrostachys juncea (JeN hybrid), but not with those from L. arenarius (NNNNXXXX octoploid) and all tetraploid Leymus species (NNXX). Attempts to cross diploid Thinopyrum and tetraploid Leymus species yielded only one triploid hybrid, T. elongatum × L. salinus ssp. salmonis. Meiotic chromosome associations at metaphase I of pollen mother cells in the triploid hybrid averaged 19.69 univalents, 0.64 bivalents, and 0.01 trivalents per cell. Chromosome pairings in the tetraploid hybrids of L. mollis × L. salinus ssp. salmonis, and the reciprocal cross, indicate that L. mollis and L. salinus ssp. salmonis shae the same genomic constitution. Both the DNA probe and genome analysis results confirm the absence of the J genome in the seven additional Leymus species tested. Meiotic data indicated that tetraploid Leymus species could not have the genome formula N1N1N2N2; thus their genome formulas should remain as NNXX until the source of X is identified.Key words: genome, Leymus, DNA probe, Southern blot, meiotic pairing, hybrid.
New mutations that suppress mating-type vegetative incompatibility in Neurospora crassa
Authors: Vellani Tia S. , Griffiths Anthony J. F. , Glass N. Louise
Published: May 2008

The mating-type locus in the ascomycete Neurospora crassa functions as a vegetative-incompatibility locus during asexual growth such that A + a heterokaryons and A/a partial diploids are inhibited in their growth. In this study, we sought mutations that suppress mating-type associated vegetative incompatibility by using A/a partial diploids. Mutants were selected as spontaneous escapes from inhibited growth. Suppressors were identified by selecting escapes that retained the capacity to mate with both A and a strains. The escaped partial diploids were then outcrossed to remove the duplication. Seven suppressors were identified that segregated as single, recessive mutations. All seven of the suppressors were shown to be allelic to a previously obtained suppressor, tol, by segregation analyses and heterokaryon tests. This result indicates that all seven mutations are new alleles of tol and suggests that tol is a key regulatory locus in the expression of mating-type associated vegetative incompatibility in N. crassa.Key words: vegetative incompatibility, mating type, suppressors, Neurospora.
Intravarietal variation in satellites and C-banded chromosomes of Agropyron intermedium ssp. trichophorum cv. Greenleaf
Authors: Xu Jie , Conner R. L.
Published: May 2008

A high amount of intravarietal variation in satellites and C-banded chromosomes was observed in the hexaploid wheatgrass synthetic cultivar 'Greenleaf' (Agropyron intermedium ssp. trichophorum (Link) A. &Gr., 2n = 6x = 42, genome E1E1E2E2SS). The cultivar is an open-pollinated perennial that shows extensive interplant polymorphism for many biological characters. Maximum number of satellites detected varied among plants from zero to six. In 61% of the plants, we observed two large satellites in association with zero, one, or two small ones. Chromosome constitution differed significantly among plants as revealed by analysis of variance based on the total number of banded chromosomes and the number of banded chromosomes with telomeric bands at either one or both ends. Heteromorphism in C-banding patterns between homologues was found in most of the chromosomes and was classified into four types: (i) difference in band size, (ii) difference in presence/absence of one or two bands, (iii) completely different banding patterns, and (iv) banded versus unbanded. Homologous chromosomes having types iii and iv heteromorphism could only be matched by their relative length and arm ratio instead of C-banding patterns. Deletions were detected in two chromosomes. Overall, C-banded chromosomes of this cultivar were characterized by the presence of large telomeric bands and were quite different from the previously reported karyotypes of the supposed diploid ancestor Agropyron elongatum (Host) P. Beauv. (genome EE) and an Ag. intermedium (Host) P. Beauv. accession (E1E1E2E2SS) The results suggest that dramatic chromosome modifications have occurred in this species during the course of evolution. The study sheds light on the extent of intrapopulation polymorphism present in the karyotypes of outcrossing polyploids and synthetic cultivars and has implications regarding strategies for chromosomal manipulation involving open-pollinated species.Key words: Agropyron intermedium ssp. trichophorum, intravarietal variation, satellites, C-banded karyotype.
The use of RAPD for identifying and classifying Musa germplasm
Authors: Howell Elaine C. , Newbury H. John , Swennen Rony L. , Withers Lyndsey A. , Ford-Lloyd Brian V.
Published: May 2008

Using the technique of random amplified polymorphic DNA (RAPD), we have identified 116 amplification products in Musa germplasm using nine primers. This has enabled us to identify RAPD markers that are specific to each of nine genotypes of Musa representing AA, AAA, AAB, ABB, and BB genomes. The pattern of variation observed following the application of multivariate analyses to the RAPDs banding data is very similar to the pattern of variation defined using morphological characters and used to assign Musa material into the different genome classes.Key words: RAPD, Musa, genome, banana, plantain, genetic variation.
P element mediated germ line transformation of Drosophila melanogaster with the Tc1 transposable DNA element from Caenorhabditis elegans
Authors: Szekely A. Alex , Woodruff R. C. , Mahendran R.
Published: May 2008

Questions relating to the origin and regulation of mobile genetic elements are currently of considerable interest. Since it is now possible to address more precisely issues concerning the entry, dispersion, and regulation of elements within a virgin genome, one approach that may afford a better understanding of transposable elements in general could be provided by interspecific DNA transformation. Therefore, the Tc1 transposable DNA element from Caenorhabditis elegans was chosen as a proposed invading element of the Drosophila melanogaster genome. The basis for this selection resided in the inherent structural and functional similarities, as well as sequence identities, between the Caenorhabditis element and elements innate to Drosophila (e.g., P, HB1, and Uhu). Initial investigations were carried out to define a clone carrying an intact Tc1 element. This Tc1 element was inserted into a P transposon vector and two P–Tc1–ry+ constructs, differing only in insert orientation, were identified. P element mediated germ line transfer was then used to generate a transformant that was genetically and molecularly identified as containing a single, structurally intact Tc1 element at cytological location 64C4-5 on the third chromosome. The single P[(Tc1, ry+)]SAS-B insertion was thereafter mobilized by using a P[ry+Δ2-3] element as a transposase source, and the genetic and molecular data suggested that the insertion had been successfully reintegrated to a variety of genomic locations. On the basis of genetic and molecular analyses, the Tc1 element in the P[(Tc1, ry+)] transformed stock is not highly unstable in germ line and somatic tissues.Key words: Tc1 transposable element, transformation, Drosophila melanogaster, Caenorhabditis elegans, P elements.
Genomic diversity and multiple origins of tetraploid (2n = 78, 80) Glycine tomentella
Authors: Kollipara Krishna P. , Singh Ram J. , Hymowitz Theodore
Published: May 2008

Among 15 wild perennial species of the genus Glycine Willd. subgenus Glycine, G. tomentella is exceptional. It is composed of four cytotypes (2n = 38, 40, 78, 80), is diverse in morphological features, and covers a wide geographical area. The objectives of this study were to uncover the genomic diversity in 78- and 80-chromosome cytotypes through a multidisciplinary approach, using cytogenetic, biochemical, and molecular methods, to verify previously identified isozyme groupings and to determine their possible origins. The cytogenetic observations, total seed protein and protease inhibitor profile comparisons, and the phylogenetic analysis of restriction fragment length polymorphisms identified three distinct groups (T1, T5, T6) among aneutetraploid (2n = 78) and four distinct groups (T2, T3, T4, T7) among tetraploid (2n = 80) G. tomentella accessions. The groupings were congruent with those of isozyme analysis. Tetraploid accessions from Indonesia were assigned to a new group, T7, based on the present study. Morphology, cytology, and seed protein banding patterns of synthetic tetraploids indicated that the T1 and T5 group aneutetraploids were composed of D3D3EE and AAEE genomes, respectively, and the T2 group tetraploid accessions consisted of AAD3D3 genomes. Various groups within the 78- and 80-chromosome G. tomentella were suggested to have originated in Australia by allopolyploidization, most likely through multiple independent events.Key words: Glycine tomentella, RFLP, seed protein profiles, protease inhibitors, synthetic alloploids.