bluuebunny/crossref_metadata_2025 huggingface dataset:
Cytogenetic variation in rye regenerated plants and their progeny
Authors: Linacero R. , Vazquez A. M.
Published: April 2011

Regenerated plants obtained from immature embryo-derived calluses of four cultivars of rye, as well as their progeny, were cytologically analyzed. Chromosome number modified plants were found among the regenerants. The progeny of apparently normal diploid regenerated plants was tested and in some cases chromosomally abnormal plants appeared. Equally, meiotic abnormalities were observed in some of the regenerated plants and their progenies. The cytological variations observed were inheritable and in some cases both types of abnormalities could be related. The nature of the variations is discussed.Key words: Secale cereale, somaclonal variation, nondiploid plants, meiotic abnormalities.
The effect on meiotic synapsis of a recombination modulator in Petunia hybrida
Authors: Abirached-Darmency M. , Tarenghi E. , Jong J. H. de
Published: April 2011

In Petunia hybrida, a major gene called Rm1 is able to induce a considerable increase in the meiotic recombination rates. To monitor the effect of Rm1 on meiotic synapsis, synaptonemal complex (SC) formation was investigated in pollen mother cells of Rm1 Rm1 and rm1 rm1 plants. Three-dimensional serial-section reconstruction showed no morphological difference in their SC structure. In two-dimensional spreading nuclei, although extensive SC formation was observed in the absence of Rm1, our observations strongly suggest that SC formation is more regular and more efficient in the presence of Rm1. SC analysis showed that the reduced chiasma frequency observed in rm1 rm1 plants corresponds to a partial failure of synapsis involving chromosome ends, pericentric regions, and may also extend to the whole length of short chromosome arms. It is proposed that Rm1 probably corresponds to a regulatory system with multiple effects, including the course of synapsis and the extent and quality of SC formation.Key words: synaptonemal complex, synapsis, chiasma, recombination modulator gene, petunia.
The basis of decreased recombination in certain outcrosses of Neurospora crassa
Authors: Perkins David D. , Bojko Maja
Published: April 2011

Crossing over in a multiply marked segment of linkage group I was conspicuously reduced in outcrosses between a marked laboratory strain and each of six unrelated wild-collected strains, compared with crosses between inbred laboratory strains. The marked chromosome segment was transferred intact from the inbred strain to one of the wild-collected strains by seven recurrent backcrosses, and conversely, the corresponding segment of the wild strain was transferred to the inbred background by backcrossing to the multiply marked laboratory strain. Recombination was then monitored in crosses from parents having the marked and unmarked chromosome segments from the same or from unrelated sources. Meiotic crossing-over in the marked segment remained low in crosses between parents that were dissimilar with respect to genetic background, but crossing over was restored to a high level when the genetic background of both parents was that of the inbred laboratory strain, regardless of the source of the marked segments. Reduced recombination in outcrosses was therefore not due to heterologies in the marked segment but must be attributed to modifiers that are unlinked or distant from the monitored region.Key words: recombination, recombination control, crossing over, Neurospora.
Genetic analysis of major multigene families in Brassica oleracea and related species
Authors: Kianian Shahryar F. , Quiros Carlos F.
Published: April 2011

Sequences homologous to rRNA, napin, cruciferin, self-incompatibility, isocitrate lyase, and malate synthase were mapped to the Brassica oleracea genome. Four segregating populations were used to disclose possible distortions in segregation and linkage ratios while maximizing detectable polymorphism. rRNA mapped to three unlinked loci, which reside on different chromosomes. Certain restriction fragment length polymorphism variations detected by the rDNA probe reflect changes in the number of intergenic spacer subrepeats, the size of which was estimated to be about 300 base pairs. All five napin, three self-incompatibility, and two isocitrate lyase loci mapped in linkage clusters, while those of cruciferin and malate synthase (two loci each) were independent.Key words: Brassica oleracea, RFLP analysis, linkage analysis, multigene family.
Identification of a Triticum–Lophopyrum noncompensating translocation line and detection of Lophopyrum DNA using a wheatgrass specific molecular probe
Authors: Kim Nam-Soo , Whelan Ernest D. P. , Fedak George , Armstrong Ken
Published: April 2011

A Triticum–Lophopyrum translocation line was produced by a series of backcrosses between F1 hybrids derived from the cross Triticum aestivum × Lophopyrum ponticum (Podp.) Love and their progenies and bread wheat. Cytogenetic studies of progeny of crosses between the wheat-alien translocation line and doubled ditelosomics of the group 5 homoeologues of 'Chinese Spring' indicated that the translocated chromosome consisted of the long arm of chromosome 5B of wheat and short (S) arm of chromosome 6 (6AgS) of decaploid L. ponticum (2n = 70), which carries the gene(s) for resistance to colonization by wheat curl mite (Eriophyes tulipae Keifer). The frequencies of resistance to mite colonization were similar (p = 0.64) for F1 progenies from crosses between the noncompensating translocation line and double ditelosomics for 5A, 5B, and 5D and averaged 61.4%, but the frequency of F2 seeds per head (11.8) was lowest (p > 0.05) for hybrids involving 5B double ditelosomics. A repetitive DNA probe found abundantly in wheatgrass was also used to detect the Lophopyrum chromatin in this wheat-alien translocation plant. Although this probe hybridized faintly to wheat DNA in Southern hybridization, the probe's diagnostic hybridization to DNA from the wheat-Lophopyrum translocation plant clearly showed the presence of Lophopyrum DNA.Key words: wheat, Lophopyrum, wheatgrass, Eriophyes tulipae, translocation, hybrids, repetitive DNA sequence.
Comparative genetic analyses of F2 plants and anther culture derived plants of maize
Authors: Bentolila S. , Hardy T. , Guitton C. , Freyssinet G.
Published: April 2011

The doubled haploid (DH) lines represent a potentially powerful tool in maize genetics and breeding. The goal of this work was to test the ability of the DH lines to be used in these research areas. This was achieved by comparing the segregation and recombination of 94 restriction fragment length polymorphism (RFLP) markers in an F2 population and an anther culture (AC) derived population of maize (Zea mays L.). These were obtained from the cross of R6 (an elite maize line of Mo17/Oh43 group, not responsive to anther culture) with DH89.1 (a maize line very responsive to anther culture provided by Dr. M. Beckert). Despite the single factor disturbed segregations and the impossibility to discriminate between the loose and numerous spurious linkages detected with DH data, a linkage map could be constructed. The comparison of the DH linkage map with the F2 linkage map demonstrated two points. First, the markers order is conserved between the two maps. Second and most importantly, 97% of the length covered by the DH map proved to be consistent with the F2 map. These results are discussed in relation to the use of DH lines in maize breeding and gene mapping.Key words: corn, doubled haploid lines, restriction fragment length polymorphism markers, disturbed segregation, mapping.
The effect of genotype × cytoplasm interaction on meiotic behaviour of maize chromosomes
Authors: Kruleva M. M. , Korol A. B. , Dankov T. G. , Skorpan V. G. , Preygel I. A.
Published: April 2011

The effect of four isogenic cytoplasmic types, normal, Salvador, Texas, and Charrua (the latter three causing male sterility), on the process of chiasma formation has been studied using two different maize hybrids. The cytoplasmic male sterility determinants have been shown to reduce the rate of interstitial exchanges per nucleus and per bivalent and the frequency of univalents. Increased variation between plants and relative stability of the intercellular variation within a plant have been observed for the parameters studied. It is concluded that the determinants of cytoplasmic sterility lower the probability of additional exchanges (relative to the obligate one) and reduce the frequency of premature disruption of one-exchange chromosome associations.Key words: maize, chiasma frequency, male sterile cytoplasm, univalent formation, genotype × cytoplasm interaction.
X chromosome inactivation in X autosome translocation carrier cows
Authors: Basrur P. K. , Pinheiro L. E. L. , Berepubo N. A. , Reyes E. R. , Popescu P. C.
Published: April 2011

The pattern of X chromosome inactivation in X autosome translocation carriers in a herd of Limousin–Jersey crossbred cattle was studied using the reverse banding technique consisting of 5-bromodeoxyuridine incorporation and acridine orange staining and autoradiography on cultures of solid tissues and blood samples exposed to tritiated thymidine. The late-replicating X chromosome was noted to be the normal X in strikingly high proportions of cells in cultures of different tissues from all translocation carriers. It is suggested that the predominance of cells in which the normal X is inactivated may be the result of a postinactivation selection process. Such a selection process during the prenatal life favouring cells in which the genes of the normal X chromosome remain unexpressed in translocation carrier females may be the mechanism that helps these conceptuses escape the adverse effects of functional aneuploidy. Based on the observation that the translocation carriers of this line of cattle are exclusively females and that there is a higher than expected rate of pregnancy loss, it is also postulated that the altered X chromosome may be lethal to all male conceptuses and to some of their female counterparts.Key words: X inactivation, X autosome translocation, bovine chromosomes, familial translocation.
Chromosome errors at mitotic anaphase
Authors: Ford Judith Helen , Correll Anthony Thomas
Published: April 2011

Errors in mitotic divisions were assayed using various satellite DNAs as probes, hybridized in situ, to show that they included nondisjunction, chromosome and chromatid lagging, chromatid malsegregation, and monopolar segregations. The total rates of error were 1.7, 1.1, and 0.6% for chromosomes X, 17, and 18, respectively. Lagging was the most common error for all chromosomes and chromatid malsegregation, a source of 3:1 segregations occurred at about the same frequency as nondisjunction. In some cells, lagging of both X chromatids occurred and there were several cells where both X chromosomes showed errors in segregation. The disjunction of chromosomes was shown to be independent of their segregation and is speculated to involve a different mechanism.Key words: nondisjunction, lagging, in situ, satellite DNA, aneuploidy.
Genome analysis of Thinopyrum junceiforme and T. sartorii
Authors: Liu Zhi-Wu , Wang Richard R.-C.
Published: April 2011

Genome constitutions of Thinopyrum junceiforme (A. Löve and D. Löve) A. Löve (2n = 4x = 28) and T. sartorii (Boiss. &Heldr.) A. Löve (2n = 4x = 28) were determined by studying (i) meiotic pairing patterns in hybrids involving the two species and other pertinent hybrids; (ii) mitotic chromosome karyotypes based on length, arm ratio, and satellites; and (iii) C-banding patterns. New hybrids synthesized and reported are T. sartorii × T. bessarabicum (2n = 3x = 21), T. sartorii × (T. bessarabicum × T. elongatum) amphidiploid (2n = 4x = 28), and the reciprocal of the latter. Mean meiotic pairing in the triploid hybrid and the two tetraploid hybrids were 3.83 I + 3.92 II + 3.11 III, 0.931 + 7.46 II + 0.62 III + 2.44 IV + 0.07 V + 0.03 VI, and 3.41 I + 9.39 II + 0.74 III + 0.88 IV, respectively. Based on the chromosome pairing data, it can be concluded that T. junceiforme and T. sartorii have two versions (Jb and Je) of the J genome and behave like true allotetraploids owing to bivalentization. Karyotype analyses of the species and their hybrids with T. bessarabicum revealed minor structural differentiations of the genomes in the two species. Thinopyrum sartorii has one genome basically unchanged from the Jb genome of T. bessarabicum while another is a modified Je genome of T. elongatum. One genome of T. junceiforme is modified from Jb and the other is modified from Je. There are two pairs of large and one pair of small satellites in T. sartorii, but there are only one pair of each in T. junceiforme. Thinopyrum junceiforme is rich and T. sartorii is poor in interstitial C-bands for both sets of genomes. Thinopyrum sartorii has larger terminal C-bands on the Jb genome chromosomes than those of T. junceiforme. These organizational changes of chromosomes could not be detected by studying chromosome pairing alone. However, this study demonstrates that meiotic pairing is the first criterion for determining basic genome symbols. Other techniques, such as those involving chromosome banding, isozymes, and DNA probes, may then be used to detect differences in chromosome (or DNA) organization and gene expression.Key words: genome, hybrid, meiosis, karyotype, chromosome banding, speciation.
The genetic basis of seed set in barley genotypes varying in compatibility with Hordeum bulbosum
Authors: Chen F. Q. , Hayes P. M.
Published: April 2011

Low seed set, owing to partial incompatibility, can limit sexual gene transfer and haploid production efficiency in wide crosses. The inheritance of partial incompatibility in barley Hordeum vulgare L. × H. bulbosum L. crosses and its effect on gamete sampling in doubled haploid production were studied by doubled haploid progeny analysis. The dominant, monogenic control of partial incompatibility in 'Vada' was confirmed. Partial incompatibility in 'Harrington' is also monogenic but appears to be controlled by a different gene. An association between the Inc gene and a deficiency in a stigma–stylodium specific high pI protein was found in the co-segregation analysis of doubled haploid progeny. Segregation analysis of Mendelian markers in doubled haploid progeny showed that there is no evidence that the compatibility status of the parents has an effect on gamete sampling by the bulbosum technique.Key words: barley, haploids, Hordeum bulbosum, incompatibility.
Chromosomes and DNA of Anguilla anguilla: a study with restriction endonucleases
Authors: Cau A. , Coluccia E. , Deiana A. M. , Pichiri G. , Rossino R. , Salvadori S. , Mezzanotte R.
Published: April 2011

We have studied fixed chromosomes and purified DNA of Anguilla anguilla L. after digestion with HaeIII, AluI, MboI, and DdeI restriction endonucleases. Our data demonstrated (i) confirmation of the heteromorphic nature of NORs, (ii) absence of detectable sex chromosomes, and (iii) presence of discrete intercalary domains in this species. Our data also permitted us to hypothesize the existence of highly repetitive DNAs, localized in specific heterochromatic regions of A. anguilla chromosomes.Key words: fish, chromosomes, DNA, restriction enzymes.
Genetic and cytogenetic analyses of the A genome of Triticum monococcum. VII. Telotrisomics and a ditelotetrasomic
Authors: Kim Nam-Soo , Kuspira J.
Published: April 2011

Telotrisomics (2n = 14 + t) were obtained from primary trisomics for chromosome 5A in Triticum monococcum. Subsequently, a ditelotetrasomic (2n = 14 + 2t) plant was obtained from these telotrisomics. C-banding analysis revealed that the extra telocentric chromosome in these aneuploids consisted of the short arm of chromosome 5A (triplo 5AS). Of 78 meiocytes studied at diakinesis and metaphase I in the telotrisomics, 20 (27.0%), 46 (58.9%), and 12 (14.1%) showed 6 II + 1 III,6 II + 3 I, and 7 II + 1 I configurations, respectively. Although the majority of the cells (84%) at anaphase I (AI) in the telotrisomics showed a 7–8 chromosome segregation, chromosome laggards were also observed. Their frequency (16%) was much higher than in primary trisomics. In a ditelotetrasomic plant, 14, 6, 8, and 4 cells of the 42 meiocytes studied showed 6 II + 1 IV, 7 II + 2 I, 6 II + 1 III + 1 I, and 8 II configurations, respectively. Approximately 62% of the meiocytes at AI in this plant showed an 8–8 chromosome segregation. Compared with primary trisomics and diploids, telotrisomics showed an intermediate phenotype for many of the characters studied. The telotrisomics headed earlier than primary trisomics, but later than diploids. The ditelotetrasomic headed much later than the telotrisomics. The ditelotetrasomic plant also showed very deleterious phenotypes such as slow growth and degeneration of tillers during the later stage of growth. An average of 51.7% of the florets of the telotrisomics exhibited seed set under greenhouse growing conditions. Fertility of the ditelotetrasomic plant on the other hand was very low (2.5%) under the same growing conditions.Key words: Triticum monococcum, C-bands, A genome.
Variation in the restriction fragments of 18S–26S rRNA loci in South American Elymus (Triticeae)
Authors: Dubcovsky Jorge , Lewis Silvina M. , Hopp Esteban H.
Published: April 2011

The repeat units of the 18S–5.8S–26S ribosomal genes (rDNA) of 15 South American and 6 Asiatic and North American species of Elymus were shown to vary between 8.7 and 11.3 kb among species. Interspecific variation in the EcoRI and BamHI cleavage sites was observed. BamHI restriction sites were present in the subrepeats in the intergenic spacers in rDNA from diploid Hordeum (H genome) and absent in the diploid Pseudoroegneria (S genome) and in nearly all the tetraploid species of Elymus (SH genomes). Tetraploid Elymus species have only two pairs of chromosomes with secondary constrictions similar to those found in Pseudoroegneria and a maximum of two different repeat unit length classes. These results suggest that the rDNA in the H genome was lost during the evolution of the tetraploid Elymus. However, the additional H genome present in the hexaploid Elymus with genome formula SSHHH′H′ still show active ribosomal genes. Nucleolar organizer activity was also observed in rDNA from both the S and H genomes in artificial SS × HH amphiploids, suggesting no complete nucleolar dominance (amphiplasty) between the S and H genomes.Key words: Elymus, ribosomal genes, RFLP, nucleolus.
Mitochondrial and ribosomal DNA variation among members of the Anopheles quadrimaculatus (Diptera: Culicidae) species complex
Authors: Mitchell Sharon E. , Narang Sudhir K. , Cockburn Andrew F. , Seawright J. A. , Goldenthal Michael
Published: April 2011

The extent of intra- and inter-specific variation in mitochondrial DNA and nuclear ribosomal RNA gene restriction sites was determined for the four sibling species of the Anopheles quadrimaculatus complex. Individual mosquitoes were identified by allozyme analysis according to previously published keys, and the total genomic DNA of these same individuals was then cleaved with restriction enzymes. Restriction maps of mitochondrial DNA, including the positions of variable sites, were constructed for each species. No evidence for interspecific hybridization was found in the populations surveyed. There was little variation in restriction patterns within any given species, but differences occurred among the four. Three restriction enzymes (AvaI, HindIII, and PvuII) yielded species-specific DNA restriction patterns for the mitochondrial DNA, while AvaI and HindIII produced diagnostic patterns for the ribosomal DNA. Thus, restriction patterns were very useful for detecting cryptic species but less appropriate than isozymes for studying genetic structure of populations within species.Key words: mtDNA, rDNA, Anopheles quadrimaculatus, species complex, sibling species.
Amphidiploids of perennial Triticeae. I. Synthetic Thinopyrum species and their hybrids
Authors: Wang Richard R.-C.
Published: April 2011

Amphiploids of the hybrid Thinopyrum elongatum (Host) D.R. Dewey (2n = 2x = 14; JeJe) × Pseudoroegneria spicata (Pursh) A. Löve (2n = 2x = 14; SS) were obtained by the colchicine treatment of regenerants from inflorescence culture. Meiotic pairings in the JJSS amphiploids averaged 2.90 I + 4.44 rod II + 7.50 ring II + 0.14 III + 0.20 IV at metaphase I but had 13.38 ring II + 0.30 IV at diakinesis. This amphidiploid was crossed with that of T. bessarabicum (Savul. &Rayss) A. Löve (2n = 2x = 14; JbJb) × T. elongatum and the latter was also crossed with T. scirpeum (K. Presl) D.R. Dewey (2n = 4x = 28; JeJeJeJe) to obtain JbJeJeS and JeJeJeJb hybrids, respectively. The former hybrid had a metaphase I pairing pattern of 7.82 I + 4.33 rod II + 2.76 ring II + 1.51 III + 0.35 IV. The latter hybrid had 3.04 I + 4.05 rod II + 4.31 ring II + 1.26 III + 1.08 IV. These meiotic pairing data are in agreement with the genomic relationships based on the diploid hybrids involving these genomes. Fertility of the hybrid between T. scirpeum and the amphiploid of T. bessarabicum × T. elongatum suggested that their genomes were similar and balanced and that gene flow could occur between the JJ diploids and the JJJJ tetraploid.Key words: hybrid, amphidiploid, genome, isozyme, chromosome pairing, Triticeae, Thinopyrum.
The phylogeny of nine species of the Drosophila obscura group inferred by the banding homologies of chromosomal regions. III. Element D
Authors: Brehm Antonio , Krimbas Costas B.
Published: April 2011

The phylogenetic relationships among nine species belonging to the obscura group of the genus Drosophila were deduced, based on similarities of the banding pattern of their polytene chromosomal element D. These similarities were inferred by the comparison of chromosomal photomaps. The phylogenetic reconstruction was the most parsimonious based on seriation by overlapping inversions and on the principle of conservation/disassociation of nearby located segments. The gene sequences of element D for all species studied were relatively easy to recognize in terms of the map of D. obscura, already found to occupy a relative central position in this group. Thus, three clusters of closely related species could be identified: obscura (D. obscura, D. ambigua, and D. tristis), African (D. kitumensis and D. microlabis), and subobscura (D. subobscura, D. madeirensis and D. guanche), with D. subsilvestris standing apart. The results are in agreement with those from the previously studied elements B and E, but element D was found to be much more conclusive concerning the links among the different clusters. Thus, it is inferred that D. guanche occupies an intermediate position between the other two species of its own cluster and all the others. The gene arrangement of D. obscura, directly related to those of the other species, has been identified. In the phylogenetic tree proposed, both the African cluster and D. subsilvestris derive from a hypothetical gene arrangement, intermediate in the pathway between the subobscura and obscura clusters.Key words: Drosophila obscura group, phylogeny, chromosomal inversions, element D, chromosomal gene arrangements.
Digestion of human chromosomes by means of the isoschizomers MspI and HpaII
Authors: Fernandez-Peralta A. M. , Navarro P. , Tagarro I. , Gonzalez-Aguilera J. J.
Published: April 2011

The isoschizomers MspI and HpaII are four base cutter (C↓CGG) restriction endonucleases, HpaII being sensitive to methylation of the internal cytosine. Human chromosomes treated with MspI have produced inconsistent results between laboratories, while HpaII has always been described as a nonbanding enzyme when used on human chromosomes. These results have been explained on the basis of both rarity of the CpG doublet in vertebrate genomes and high rate of CpG methylation (5mCpG). We demonstrated consistent banding patterns subsequent to digestions with MspI and HpaII. On euchromatin, MspI (but not HpaII) digests the DNA of R regions and thus R-bands apparently contain many more CCGG sites (mostly methylated) than G-bands. In heterochromatin, extensive digestion of the 9q12 region not only by MspI but also by HpaII reveals a heterochromatic domain with a high frequency of unmethylated CCGG sites, most probably within the satellite 3 DNA fraction. In addition, enzymatic digestions of the Yq12 heterochromatin, when this region is undercondensed by 5-azacytidine, contribute to deepen the insight into the mechanism of action of this cytidine analog and at the same time reinforce the idea of the heterogeneity of this chromosome region where domains with unmethylated CCGG sites may also exist.Key words: human chromosomes, methylation, restriction endonucleases, heterochromatin, satellite DNA.
Molecular genetic identification ofAvenachromosomes related to the group 1 chromosomes of the Triticeae
Authors: Jellen E. N. , Phillips R. L. , Rooney W. L. , Rines H. W.
Published: April 2011

A collection of 19 wheat (Triticum aestivum) probes, detecting sequences in the seven homoeologous groups of chromosomes, were hybridized to DNA from the 'Kanota' series of oat monosomic lines (Avena byzantina) to investigate their use for identifying groups of homoeologous oat chromosomes. Three probes from homoeologous group 1 of wheat, psr161, psr162, and psr121, mapped among the set of oat chromosomes 1C, 14, and 17. One homoeologous group 6 probe, psr167, mapped to oat chromosomes 1C and 17. Two oat probes that had previously been shown to map to oat chromosomes 1C, 14, and 17 were then hybridized to DNA from the 'Chinese Spring' wheat ditelosomics. They localized to homoeologous group 1 wheat chromosomes, one to the short arm and one to the long arm. These results reveal that in hexaploid oat there is a group of three chromosomes that correspond at least in part to homoeologous group 1 of wheat. The remaining wheat probes identifying other wheat homoeologous sets did not detect a complete series of homoeologous chromosomes in oat. This was presumably due to the incomplete status of the 'Kanota' monosomic series, chromosomal rearrangement in Avena, weak hybridization signals owing to low probe-target sequence homology, and (or) detection of only two hybridization bands by the wheat probe.Key words: oat, RFLPs, aneuploids, wheat, homoeologous groups.
Targeted mapping of rye chromatin in wheat by representational difference analysis
Authors: Delaney Donna E. , Friebe Bernd R. , Gill Bikram S. , Hulbert Scot H. , Hatchett James H.
Published: April 2011

A targeted mapping strategy using representational difference analysis (RDA) was employed to isolate new restriction fragment length polymorphism probes for the long arm of chromosome 6 in rye (6RL), which carries a gene for resistance to Hessian fly larvae. Fragments from the 6RL arm were specifically isolated using a 'Chinese Spring' (CS) wheat – rye ditelosomic addition line (CSDT6RL) as tester, and CS and (or) CS4R as the driver for the genomic subtraction. Three RDA experiments were performed using BamHI amplicons, two of which were successful in producing low-copy clones. All low-copy clones were confirmed to have originated from 6RL, indicating substantial enrichment for target sequences. Two mapping populations, both of which are derived from a cross between two similar wheat–rye translocation lines, were used to map five RDA probes as well as five wheat probes. One of the populations was prescreened for recombinants by C-banding analysis. Fifteen loci, including seven new RDA markers, were placed on a map of the distal half of 6RL. The Hessian fly resistance gene was localized by mapping and C-banding analysis to approximately the terminal 1% of the arm. The utility of RDA as a method of targeted mapping in cereals and prospects for map-based cloning of the resistance gene are discussed.Key words: Secale cereale L., Hessian fly resistance; RDA, RFLP, high density mapping.
Inheritance and linkage relationships of seed peroxidase loci in hexaploid oat (Avena sativa L.)
Authors: Sharopova N. R. , Sozinov A. A. , Portyanko V. A.
Published: April 2011

Polyacrylamide gel electrophoresis has been used to investigate the inheritance and linkage relationships between anodal (PXA) and cathodal (PXC) seed peroxidases in hexaploid oat (Avena sativa L.). A total of 12 seed peroxidase loci (5 loci of PXA and 7 loci of PXC) were identified in three crosses. Only two Pxc loci (Pxc5 and Pxc7) were not linked to any peroxidase loci; the others were scored in three linkage groups. The order of the three loci assigned to one of the linkage groups was Pxc1–Pxa5–Pxc2. The order of loci in the other two linkages were Pxc4–Pxa1–Pxa3 and Pxc3–Pxa4–Pxa2. Also, the Pxc6 locus was shown to be linked to the Pxc3 locus. Considering that A. sativa is an allohexaploid, it can be proposed that the three peroxidase linkages represent homoeologous chromosomes.Key words: seed peroxidase, isozyme inheritance, linkage, Avena sativa.
Hypervariability of ribosomal DNA at multiple chromosomal sites in lake trout (Salvelinus namaycush)
Authors: Zhuo Lang , Reed Kent M. , Phillips Ruth B.
Published: April 2011

Variation in the intergenic spacer (IGS) of the ribosomal DNA (rDNA) of lake trout (Salvelinus namaycush) was examined. Digestion of genomic DNA with restriction enzymes showed that almost every individual had a unique combination of length variants with most of this variation occurring within rather than between populations. Sequence analysis of a 2.3 kilobase (kb) EcoRI–DraI fragment spanning the 3′ end of the 28S coding region and approximately 1.8 kb of the IGS revealed two blocks of repetitive DNA. Putative transcriptional termination sites were found approximately 220 bases (b) downstream from the end of the 28S coding region. Comparison of the 2.3-kb fragments with two longer (3.1 kb) fragments showed that the major difference in length resulted from variation in the number of short (89 b) repeats located 3′ to the putative terminator. Repeat units within a single nucleolus organizer region (NOR) appeared relatively homogeneous and genetic analysis found variants to be stably inherited. A comparison of the number of spacer-length variants with the number of NORs found that the number of length variants per individual was always less than the number of NORs. Examination of spacer variants in five populations showed that populations with more NORs had more spacer variants, indicating that variants are present at different rDNA sites on nonhomologous chromosomes.Key words: ribosomal DNA, lake trout, intergenic spacer, repetitive DNA.
Structure and expression of histone H3.3 genes inDrosophila melanogasterandDrosophila hydei
Authors: Akhmanova Anna S. , Bindels Petra C. T. , Xu Jie , Miedema Koos , Kremer Hannie , Hennig Wolfgang , Xu Jie , Hennig Wolfgang
Published: April 2011

We demonstrate that in Drosophila melanogaster the histone H3.3 replacement variant is encoded by two genes, H3.3A and H3.3B. We have isolated cDNA clones for H3.3A and cDNA and genomic clones for H3.3B. The genes encode exactly the same protein but are widely divergent in their untranslated regions (UTR). Both genes are expressed in embryos and adults; they are expressed in the gonads as well as in somatic tissues of the flies. However, only one of them, H3.3A, shows strong testes expression. The 3′ UTR of the H3.3A gene is relatively short (~250 nucleotides (nt)). H3.3B transcripts can be processed at several polyadenylation sites, the longest with a 3′ UTR of more than 1500 nt. The 3′ processing sites, preferentially used in the gonads and somatic tissues, are different. We have also isolated the Drosophila hydei homologues of the two H3.3 genes. They are quite similar to the D. melanogaster genes in their expression patterns. However, in contrast to their vertebrate counterparts, which are highly conserved in their noncoding regions, the Drosophila genes display only limited sequence similarity in these regions.Key words: H3.3 histone variant, Drosophila, sequence comparison, alternative polyadenylation, testis expression.
Mechanisms and inheritance of first division restitution in hybrids of wheat, rye, and Aegilops squarrosa
Authors: Xu S. J. , Joppa L. R.
Published: April 2011

First division restitution (FDR) in intergeneric Triticeae hybrids provides an important meiotic mechanism for the production of amphidiploids without the use of colchicine and similar chemicals. The genetic controls of FDR were investigated by examining microsporogenesis and fertility in F1 hybrids of two- and three-way crosses of durum wheat (Triticum turgidum L. var. durum) cultivars Langdon (LDN) and Golden Ball (GB), 'Gazelle' rye (Secale cereale L.), and one accession (RL5286) of Aegilops squarrosa L. The results from two-way crosses indicated that the first meiotic division varied, depending on the hybrid. GB crossed with Ae. squarrosa developed tripolar spindles and prevented congregation of chromosomes at the equatorial plate. The hybrid of GB with rye had a delayed first division. But, the hybrids of LDN with both Ae. squarrosa and rye had a high frequency of FDR. Analysis from the three-way crosses indicated that inheritance in rye crosses differed from those with Ae. squarrosa. FDR segregated in a 1:1 ratio in the rye cross, suggesting that the FDR is controlled by a single gene from LDN. However, FDR fit a 1:3 ratio in the three-way crosses with Ae. squarrosa. Cytological data suggested that tripolar spindles are a major factor preventing FDR in Ae. squarrosa crosses. Some progenies from the three-way cross with rye had a high frequency of monads that resulted from second division failure of FDR cells.Key words: durum wheat, rye, Aegilops squarrosa, first division restitution, tripolar spindle.
Repeated DNA sequences isolated by microdissection. I. Karyotyping of barley (Hordeum vulgare L.)
Authors: Busch Winfried , Martin Regina , Herrmann Reinhold G. , Hohmann Uwe
Published: April 2011

We report on microdissection, cloning and sequence, and Southern and fluorescence in situ hybridization (FISH) analysis of one moderately and one highly amplified repetitive DNA element, pHvMWG2314 and pHvMWG2315, respectively, isolated from barley (Hordeum vulgare L.) chromosome arm 3HL. The pHvMWG2315 sequence hybridizes to all 14 telomeric or subtelomeric regions of the barley chromosomes as determined by FISH. The 50 different hybridization sites that include intercalary signals allow the discrimination of all 14 chromosome arms and the construction of a karyotype of barley. The tandemly repeated subtelomeric element of 331 bp exists in all Triticeae species tested (H. vulgare, Agropyron elongatum, Secale cereale, Triticum tauschii, T. turgidum, and T. aestivum). It is AT rich (66%), exhibits 84% sequence homology to subfragments of the D genome "specific" 1-kb element pAsl of T. tauschii and 75% homology to the interspersed genome-specific DNA sequence pHcKB6 from H. chilense. The repetitive sequence pHvMWG2314 is moderately amplified in barley and highly amplified in hexaploid wheat. The in situ experiments revealed no distinct signals on barley chromosomes, indicating a dispersed character for the sequence. The significance of the results for the identification of chromosomes and chromosome aberrations in FISH experiments are discussed.Key words: karyotype, fluorescence in situ hybridization, FISH, DNA sequencing.
Genetic and cytological mapping of a "Y–2" translocation in the Mediterranean fruit flyCeratitis capitata
Authors: Cladera Jorge L. , Delprat M. Alejandra
Published: April 2011

In this paper we analyze genetically and cytologically a Y – chromosome 2 translocation with several markers, some of which are potentially useful for large scale sex separation. The breakpoint of this Y–2 translocation is located at region 6B on the trichogene polytene chromosome map. It was found that, in strains carrying this TY–2, only 40% of the fertilized eggs survived to the adult stage, 26% of them dying as embryos, 27% as larvae, and 7% as pupae. Early lethality is explained by the nonviability of adjacent-1 products of meiosis containing a deletion of section 1A–6B. The reciprocal segregation products, carrying this chromosome segment in triplicate, survive until late stages. By analyzing the phenotype of these individuals we conclude that all markers used in this study are located outside the triplicated region and that the male determining factor is not included in the piece of the Y chromosome translocated to chromosome 2. The male recombination frequencies of several genes located on chromosome 2 relative to the breakpoint of translocation T5038 have also been studied here.Key words: genetic sexing strain, Medfly polytene chromosome, adjacent-1 product, translocation breakpoint mapping.
Complete meiotic pairing of crested newt chromosomes
Authors: Wallace H. , Wallace B. M. N.
Published: April 2011

The longest chromosome (number 1) of Trituturus cristatus carries a heteromorphic segment, a heterozygosity perpetuated by a balanced lethal system. The heteromorphic segment is regarded as achiasmate and has been claimed to be asynaptic. Direct observations of chromosome pairing in spermatocytes and oocytes yield some cases where all homologous chromosomes appear to be completely paired, but the individual bivalents could not be identified as pachytene is not particularly clear in this species. The long arms of bivalent 1 usually remain attached by a terminal chiasma in spermatocytes of T. c. cristatus but the corresponding chiasma is only rarely present in T. c. carnifex spermatocytes. Synaptonemal complexes have been measured in both spermatocytes and oocytes of T. c. cristatus. A karyotype constructed from these measurements matches the main features of somatic and lampbrush chromosome karyotypes, indicating that all chromosomes must be completely paired and proportionately represented as synaptonemal complex. The total length of synaptonemal complex is much the same in spermatocytes and oocytes and is similar to the length in spermatocytes of Xenopus laevis. These two amphibian examples supplement a recent survey of other vertebrate classes to reinforce its conclusion that synaptonemal complex length is not related to genome size in vertebrates.Key words: chromosome pairing, synaptonemal complex, genome size, amphibia.
Frequency of microsatellite sequences in rice (Oryza sativaL.)
Authors: Panaud Olivier , Chen Xiuli , McCouch Susan R.
Published: April 2011

This study was undertaken to estimate the relative frequencies of 13 microsatellite motifs in the rice genome as a basis for efficient development of a microsatellite map. Two dinucleotide, seven trinucleotide, and four tetranucleotide repeat motifs were end labelled and used as hybridization probes to screen genomic and cDNA libraries of rice, cv. IR36. Optimal washing temperatures for identification of clones containing specific microsatellite motifs were estimated based on washing temperatures near Td(dissociation temperature; Td = Tm− 7.6 °C). Sequencing of 20 putatively positive clones corresponding to each of 4 microsatellite motifs suggested that while Tdprovides a useful predictor of washing stringency for most of the repeats studied, those with a very high GC or AT content were most prone to error. The results from screening the rice genomic library suggest that there are an estimated 1360 poly(GA)nand 1230 poly(GT)nmicrosatellites in the rice genome, and that the relative frequency of different repeats decreased with increasing size of the motif. The most frequently observed microsatellites in the cDNA library were the same as for the genomic library, but no poly(CGG)n, poly(ATC)n, or tetranucleotide motifs were observed among cDNAs in this study.Key words: microsatellite, simple sequence repeat, SSR, simple sequence length polymorphism, SSLP.
Genetic diversity within the species Arachis duranensis Krapov. &W.C. Gregory, a possible progenitor of cultivated peanut
Authors: Stalker H. T. , Dhesi J. S. , Kochert G.
Published: April 2011

Eighteen accessions of a diploid wild peanut species (Arachis duranensis) were analyzed using morphological, intercrossing, cytological, and RFLP data. Abundant variation was found for morphological characters and for RFLP patterns both between and within accessions, and each accession could be uniquely identified by RFLP pattern. Several plants were found to be F1 hybrids between different accessions, indicating that intercrossing had occurred when these were planted for seed increase. Patterns of RFLP diversity were found to correspond with geographic distribution. Analysis of the number of RFLP fragments observed per accession indicates that additional field collections of this complex of taxa will yield additional genetic variability.Key words: peanut, Arachis hypogaea, Arachis spp., RFLP, variation, genetic diversity.
The expression of aluminum stress induced polypeptides in a population segregating for aluminum tolerance in wheat (Triticum aestivum L.)
Authors: Somers Daryl J. , Gustafson J. Perry
Published: April 2011

This study examined the changes in gene expression induced by aluminum (Al) stress in wheat root tips. Seedlings of Triticum aestivum L. cvs. Katepwa (Al sensitive), Maringa (Al tolerant), and Alikat (Al tolerant near isoline; 'Katepwa'*3/'Maringa') and a F2 population derived from 'Katepwa' × 'Alikat', were grown for 3 days in either 0 or 1 μg∙mL−1 Al. Polypeptides were labeled with 35S-methionine prior to separation by gel electrophoresis. There were a few polypeptides from whole cell lysates that showed enhanced expression in all of the genotypes in 1 μg∙mL−1 Al, however, the whole cell lysate and microsomal polypeptide profiles also revealed numerous unique changes in gene expression in Al-sensitive 'Katepwa' at 1 μg∙mL−1 Al; the latter cosegregated with only the Al-sensitive F2 bulks. The microsomal polypeptide profiles of the Al-tolerant lines 'Maringa' and 'Alikat' changed marginally in the presence of Al and these changes were also reflected in the Al-tolerant F2 bulks. The data showed that there were many changes in gene expression which cosegregated with Al sensitivity and suggest that Al tolerance in wheat may rely on constitutively expressed polypeptides.Key words: wheat, aluminum, protein synthesis, segregation.
FokI DNA repeats in the genome of Vicia faba: species specificity, structure, redundancy modulation, and nuclear organization
Authors: Maggini F. , D'Ovidio R. , Gelati M. T. , Frediani M. , Cremonini R. , Ceccarelli M. , Minelli S. , Cionini P. G.
Published: April 2011

Tandemly repeated DNA sequences about 60 bp in length, which may be isolated by digestion with FokI restriction endonuclease, were studied by means of molecular and cytological hybridizations in Vicia faba and other Vicia species. The results obtained can be summarized as follows: (i) FokI repeats are almost species specific to V. faba, since they hybridize to a minimum extent to the genomic DNA of only two out of five related species; (ii) these tandemly repeated elements display variability in structure even within one and the same array, where different repeats may share not more than 71% homology; (iii) their redundancy in the genome of V. faba is remarkably high and varies largely between land races (copy numbers per haploid, 1C, genome range from 21.51 × 106 to 5.39 × 106); (iv) FokI repeats are clustered in differing amounts in each subtelocentric pair of the chromosome complement and are missing or present in a nondetectable amount in the submetacentric pair; (vi) chromosome regions that bear these repeats associate closely to varying degrees in interphase nuclei. These results are discussed in relation to possible functional roles that tandemly repeated DNA sequences such as the FokI elements might play.Key words: FokI, intraspecific DNA changes, nuclear organization, repeated DNA sequences, Vicia faba.
Restriction fragment length polymorphism based phylogenetic analysis ofAvenaL.
Authors: Alicchio Rita , Aranci Lina , Conte Lucia
Published: April 2011

We report a molecular approach to the study of the phylogenetic relationships of Avena diploid and polyploid species based on RFLP detected with three cDNA probes of nuclear genes belonging to multigenic families (low pI α-amylase, avenin, and globulin). All the probes were highly informative in the detection of polymorphism between oat species. Associations between species were determined from cluster (UPGMA) analysis based on distance values calculated from RFLP data separately for each of the two levels of ploidy. Results were in general agreement with morphology based phylogenetic analyses, confirming the large differentiation among A and C genomes in the evolution of diploid species and the genetic homogeneity among A. brevis, A. strigosa, and A. nuda and the recently discovered A. atlantica. A certain divergence was observed between two endemic species (A. canariensis and A. damascena) and the other diploid species with the A genome. The analysis of tetraploid species relationships confirms the differentiation of the barbata complex (A. wiestii, A. barbata, A. abyssinica, and A. vaviloviana) from the maroccana–murphyi–agadiriana group, which, despite some similarities in morphological and biochemical traits, seems to have accumulated deep genetic differences along its evolutionary pathway.Key words: Avena genomes, genetic distance, ploidy, RFLP, multigenic families.
Identification, characterization, and mapping of Ecm1, a locus affecting extracellular matrix production and lesion size in Cochliobolus heterostrophus
Authors: Zhu Hong , Braun Edward J , Perry Jennifer L , Bronson Charlotte R
Published: April 2011

A mutant of Cochliobolus heterostrophus lacking the outer layer of extracellular matrix around its germ tubes and hyphae was obtained by mutagenizing protoplasts. The mutant not only lacks the outer matrix, but also produces much smaller lesions on corn leaves than nonmutant strains; the area of mutant lesions averages 0.6 mm2 compared with 5.8 mm2 for nonmutant lesions. Genetic analysis demonstrated that the failure to produce the outer matrix cosegregates with the reduced lesion size, indicating that the two traits are controlled by the same locus, designated Ecm1 (\ul extracellular \ul matrix \ul deficient). The mutant retains normal growth on media and normal abilities to germinate, form appressoria, and penetrate corn leaves. This indicates that the outer matrix is not necessary for infection prior to entrance of the fungus into the leaf. It also indicates that the pathogenicity defect in this mutant is manifested after penetration. To facilitate future tests of whether the pathogenicity defect is caused by the lack of the outer matrix, Ecm1 was mapped. Seven markers linked to Ecm1 were found by analysis of amplified fragment length polymorphisms. Ecm1 maps to chromosome 4; the closest markers to Ecm1 are 5 cM distant, which is estimated to represent about 115 kb.
Localization of the (TTAGGG)n telomeric sequence in zebrafish chromosomes
Authors: Gornung E , Gabrielli I , Sola L
Published: April 2011

The distribution of the (TTAGGG)n telomeric sequence in Danio rerio (zebrafish) metaphase chromosomes was studied by fluorescence in situ hybridization. This study continues the analysis of the telomeric sequence distribution in fish and confirms that the (TTAGGG)n sequence is conserved in the telomeres of this group of vertebrates. The hybridization signals were restricted to telomeres in all the individuals analysed. With the degree of resolution currently available, no interstitial sites of the telomeric sequence were detected, which suggests that this type of hot-spot recombination site might be absent in zebrafish chromosomes.