bluuebunny/crossref_metadata_2025 huggingface dataset:
Synaptonemal complex transformations in rye microsporocytes at the diplotene stage of meiosis
Authors: Fedotova Yu. S. , Kolomiets O. L. , Bogdanov Yu. F.
Published: April 2011

The process of synaptonemal complex degradation during diplotene was studied in spreads of rye microsporocytes stained with silver nitrate at pH 3.5–4.5 and 6.0–8.0. Two different patterns of the synaptonemal complex degradation process have been observed, depending on the two staining procedures used. Progressive synaptonemal complex fragmentation observable at the higher pH appeared to be absent in staining at pH 3.5–4.5: thin connecting threads have been found in the "gaps" between the synaptonemal complex segments. Complete tracing of the synaptonemal complex degradation process was attempted and revealed the following successive steps: (i) local repulsion of lateral elements; (ii) lateral element looping in the regions of repulsion; (iii) extension of the loops; (iv) transformation of the extended loops into coils of irregular shape with a diameter of about 2 μm and a pitch of about 1.2 μm; and (v) formation of paired beanlike thickenings on a gyral coil. In asynaptic mutant sy-9 unpaired lateral elements are transformed without looping into a similar coil but with single beanlike thickenings. We conclude that synaptonemal complex lateral element loops at diplotene are invisible after the routine silver staining of microspreads (at pH about 6 and higher) and look like gaps between discontinuous synaptonemal complex segments, thus simulating the process of synaptonemal complex fragmentation.Key words: synaptonemal complex, diplotene, rye.
Nucleolar organizer regions are associated with silver-stained chromatid cores in meiotic chromosomes of grasshoppers
Authors: Giménez-Abián J. F. , Giménez-Martín G. , Suja J. A. , Rufas J. S.
Published: April 2011

Silver staining was employed to study the expression and localization of nucleolar organizer regions (NORs) and the localization and development of chromatid cores during the meiotic divisions of the grasshopper Chorthippus jucundus. NORs appear as silver-stained dots on the short arms of the L2 and L3 chromosomes and are always associated with chromatid cores. This observation provides an excellent chromosome marker to analyze the behaviour of chromatid cores during meiosis. Since both structures (NORs and chromatid cores) show a close interrelationship, we have obtained further evidence on the changes of organization that meiotic chromosomes undergo between metaphase I and anaphase I.Key words: nucleolar organizer region, meiosis, chromatid cores, chromosome structure, silver staining.
C-banding and DNA content in seven species of Tenebrionidae (Coleoptera)
Authors: Juan C. , Petitpierre E.
Published: April 2011

The relative amount of C-banded heterochromatin varies strikingly in seven species of tenebrionid beetles, from 25 to 58%, but most species show procentric bands only. Nevertheless, Gonocephalum patruele exhibits an almost completely heterochromatic X chromosome. The nuclear DNA content of Feulgen-stained spermatids has yielded up to a threefold difference, from 0.27 to 0.86 pg, which is not completely in accordance with the amount of C-banded heterochromatin. However, the genome sizes correlate significantly with the total chromosome areas at metaphase I and with the spermatid areas. Furthermore, the genome sizes agree with the subfamilial taxonomic groupings of these tenebrionids.Key words: Tenebrionidae, genome size, C-banding.
Physical mapping of the B-hordein loci on barley chromosome 5 by in situ hybridization
Authors: Clark Melody , Karp Angela , Archer Simon
Published: April 2011

Physical mapping of the B-hordein genes in barley (Hordeum vulgare cv. Betzes) was achieved by in situ hybridization of a biotin-labelled B-hordein cRNA probe to chromosome spreads. Lines trisomic for chromosome 5 showed up to 3 signals on interphase nuclei, while no more than 2 signals were observed in normal diploids. An enzyme pretreatment, which produced broken cells, increased the frequency of signal detection. A clear signal was observed on 23% of interphase nuclei and 0.025% of metaphase spreads. The B-hordein genes mapped to 46% of the distance from the centromere on the short arm of chromosome 5. These results are discussed in relation to the barley genetic map and to previous reports of in situ hybridization of low-copy and unique-copy genes in plants.Key words: in situ hybridization, Hordeum vulgare, B-hordein genes, genetic map.
Organization and evolution of the 5S ribosomal RNA gene family in wheat and related species
Authors: Dvořák J. , Zhang H. -B. , Kota R. S. , Lassner M.
Published: April 2011

Variation in restriction fragments in nullisomic–tetrasomic and ditelosomic lines of Triticum aestivum 'Chinese Spring' and disomic and ditelosomic substitutions of chromosomes of diploid species Lophopyrum elongatum, T. monococcum ssp. aegilopoides, T. tauschii, and T. umbellulatum for 'Chinese Spring' chromosomes were used to identify chromosomal loci of 5S rRNA genes (5S DNA) in wheat and related species. These loci are on wheat chromosome arms 1BS, 1DS, 5AS, 5BS, and tentatively 5DS, T. m. aegilopoides chromosomes 1A and 5A, T. tauschii chromosomes 1D and 5D, and T. umbellulatum chromosome 5U. In diploid L. elongatum a locus was detected on chromosome arm 1ES. In most genomes, the locus on chromosome 1 contains 5S DNA subfamily with short spacers and the locus on chromosome 5 contains 5S DNA subfamily with long spacers. Only a few genomes were found to be potential exceptions to this rule. Concerted evolution of the 5S DNA loci was examined in several genomes. It appeared that homogenization of spacers occurs predominantly within a locus. A scenario of the evolution of polyploid wheats and relationships among diploid species in Triticum are proposed from the observed variation among 5S DNA loci.Key words: Triticum, Lophopyrum, gene mapping, concerted evolution, wheat evolution, DNA methylation.
Chromosome banding studies of the osprey Pandion haliaetus (Aves, Falconiformes)
Authors: Kohler C. Deborah , Schaadt Charles P. , Vekemans Michel J. J.
Published: April 2011

The karyotype of the osprey Pandion haliaetus was studied using GTG, CBG, and NOR banding techniques on fibroblast cells derived from skin tissue cultures. Autosome pairs 1–25, Z, and W were identified by their GTG banding patterns. The remaining 11 pairs could not be identified individually because of their similarity and small size. CBG bands were restricted to the centromere region of each chromosome, including the W chromosome, which did not show an extensive C-positive region typical of most birds. Silver NOR banding revealed the presence of a nucleolar organizing region on chromosome 2 located at the secondary constriction near the proximal end of the long arm. The position of this nucleolar organizing region appears unique among Aves and may serve as a marker for tracing the phylogenetic origin of this monotypic family. No clear relationship to other Falconiformes was evident in the karyotype, although similarities to Accipitridae were found.Key words: osprey, Pandion haliaetus, karyotype, GTG bands, CBG bands, Ag-NOR bands.
Detection of ribosomal RNA genes in soybean, Glycine max (L.) Merr., by in situ hybridization
Authors: Skorupska Halina , Albertsen Marc C. , Langholz Kim D. , Palmer Reid G.
Published: April 2011

A biotinylated maize rRNA probe was hybridized to soybean nuclei. Hybridization was detected by using a streptavidin horseradish peroxidase biotin system. The procedure used enabled detection of heterologous complementary 18S and 25S rRNA coding genes in soybean. In diploid cultivars 'Hark' and 'Lincoln' a single pair of satellited chromosomes was present and two binding sites were detected at interphase. In plants trisomic for the satellited chromosome, three sites were observed, and in tetraploid nuclei, four sites were seen. The in situ hybridization results indicated that, for ribosomal RNA genes, Glycine max behaves as a diploid. We discuss the possibility of loss of a pair of satellited chromosomes in the evolution of soybean.Key words: biotin-labeled probe, rRNA genes, ploidy, Glycine max.
Genetic variation between and within populations of Engelmann spruce and subalpine fir
Authors: Shea Kathleen L.
Published: April 2011

The genetic structure of Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) in two adjacent sites in the Colorado Front Range was examined using allozyme data from 21 loci in spruce and 18 loci in fir. The genetic diversity measures of alleles per locus, percent loci polymorphic, and mean heterozygosity did not differ significantly between or within species. However, the observed heterozygosity (0.126 spruce, 0.081 fir) values suggest that Engelmann spruce is more genetically variable than subalpine fir. Mean inbreeding coefficients were twice as high in fir as in spruce (FIS = 0.154 spruce, 0.341 fir). There were significant differences in allele frequencies in both species between and within sites, and among age-classes, with spatial differences greater than temporal differences. F-statistics showed greater genetic differentiation within (FST = 2.3–2.6% spruce, 2.0–2.8% fir) than between sites (FST = 1.7% spruce, 1.3% fir). Both species had higher FST and genetic distance values, yet lower FIS values, for spatial subdivisions within rather than between sites. This pattern suggests that the size of a spatial subdivision, where maximum gene flow is 54 m, approximates the size of the largest panmictic unit. In contrast with studies on other conifers, these results suggest that factors such as differential selection pressures, seed dispersal patterns, and clumped spatial distribution have resulted in genetic differentiation at the microhabitat level in Engelmann spruce and subalpine fir.Key words: genetic variation, genetic structure, allozymes, Engelmann spruce, subalpine fir, microgeographic differentiation.
Quantitative analysis of meiotic chromosome pairing in triploid blueberry: evidence for preferential pairing
Authors: Vorsa Nicholi
Published: April 2011

Mathematical models have been developed to predict meiotic configuration frequency distributions for autoploid (random chromosome pairing) or preferential chromosome pairing behavior. Meiotic chromosome pairing was quantitatively analysed, relative to these models, in six highbush blueberry (Vaccinium corymbosum) triploid (2n = 3x = 36) hybrids derived from three unrelated 4x × 2x crosses. Mean trivalent per cell frequencies ranged from 3.59 to 7.89. Excess univalents were observed in triploids of one cross and are probably a result of disturbance in chiasma formation or maintenance and (or) random pairing failure. Arm chiasmate association values (a and b) ranged from 0.72 to 1.00, with the greatest difference in arm values being 0.18. Trivalent to ring bivalent (r) ratios ranged from 0.59 to 2.02. The observed configuration frequency distributions of three triploids having r-values greater than 1 did not deviate significantly from the autoploid pairing (p = 0) model frequency distribution. Frequency distributions of three triploids having r-values less than 1 deviated significantly from the autoploid model. Ranges for pairing affinity relationships include the possibility of two genomes pairing preferentially at a frequency of 77.7% (0.444 points over the random frequency of 0.333), which suggests the presence of genome divergence in blueberry. However, violation of model assumptions could seriously bias preferential pairing estimates. Segregating genetic factors also appear to be of significance in chromosome pairing behavior.Key words: autotriploids, chromosome pairing, preferential pairing, genome divergence, meiotic configurations.
Morphology and cytology of the reciprocal hybrids between Elymus trachycaulus and Elymus canadensis
Authors: Aung Taing , Walton P. D.
Published: April 2011

Reciprocal hybrids between Elymus trachycaulus (2n = 4x = 28) and Elymus canadensis (2n = 4x = 28) were generated through emasculation and hand-pollination. All the F1 hybrid plants were tetraploids (2n = 28). The F1 hybrids were readily produced (9 plants from 150 pollinated florets; 6% success) in crosses where E. canadensis was used as the pistillate parent and the hybrid plants were produced directly from the apparently normal hybrid seeds. The percentage of hybrid plants produced was lower (7 plants from 400 pollinated florets; 1.7% success) in crosses where E. trachycaulus was used as the pistillate parent, and embryo culture procedures were necessary to recover plants from the shriveled seeds produced. Distinct morphological as well as cytological differences between the reciprocal hybrids were observed. All the F1 plants from each reciprocal cross more closely resembled their pistillate parent, indicating a strong maternal influence. Chromosome pairing at metaphase I showed a very high frequency of cells with a hexavalent configuration (69–81%) and a low frequency of cells with univalents (15–23%) in hybrids produced from crosses with E. canadensis as the pistillate parent. In all hybrids produced from crosses with E. trachycaulus as the pistillate parent, chromosome pairing showed a relatively low frequency of cells with a hexavalent (12–22%), while the frequency of cells with univalents was high (78–81%). Cytology of these hybrids indicates substantial control by cytoplasmic genes on chromosome pairing behavior. Reciprocal hybridization betwen octaploid E. trachycaulus (8x) and tetraploid E. canadensis (4x) plants yielded three 2n = 42, one 2n = 41, and one 2n = 39 hybrid plants. All plants were weak and sterile and more closely resembled the octaploid parent, although some intermediate characters were apparent.Key words: Elymus, reciprocal hybrids, maternal influence, cytoplasmic genes, chromosome pairing.
Nucleolar dominance in interracial hybrids of the Steropleurus martorelli complex
Authors: Santos J. , Sentís C. , Robledo M. , Fernández-Piqueras J.
Published: April 2011

Two new chromosomal races (V and VI) of the Steropleurus martorelli complex, as well as the corresponding natural interracial hybrids, have been found in a region in southern Spain. Hybrids can be easily distinguished because they are heterozygous for a large L2 pair (submetacentric–telocentric), which in addition carries the major nucleolar organizer region (NOR). Silver staining reveals that the chromosomal rearrangement involved in the origin of these two chromosomal races does not affect the expression of the major active NOR in the parental homozygous races, but a nucleolar dominance phenomenon can be detected in the heterozygous hybrids, which tends to suppress NOR activity in the telocentric L2 chromosome from race VI.Key words: Steropleurus martorelli complex, nucleolar organizer region activity, nucleolar dominance, interracial hybrid.
Biochemical data bearing on the origin of the B genome in the polyploid wheats
Authors: Kerby K. , Kuspira J. , Jones B. L. , Lookhart G. L.
Published: April 2011

For many years each of the species Aegilops bicornis, Aegilops longissima, Aegilops searsii, Aegilops sharonensis, Aegilops speltoides, and Triticum urartu has been implicated as the donor of the B genome in the polyploid wheats. Biochemical and cytological data have revealed that T. urartu possesses a genome similar to that of T. monococcum, and therefore it may be the source of the A genome in T. turgidum and T. aestivum. This revelation therefore excludes T. urartu from the list of putative B-genome donors. To determine which of the remaining species is the source of the B chromosome set, the amino acid sequences of their purothionins were compared with that of the α1 purothionin coded for by the Pur-1B gene on chromosome 1 in the B genome of T. turgidum and T. aestivum. The residue sequences of this protein from Ae. bicornis, Ae. longissima, Ae. searsii, Ae. sharonensis, and Ae. speltoides differed by 1, 6, 1, 1, and 2 amino acid substitutions, respectively, from the α1 protein. These results suggest that either Ae. bicornis, Ae. searsii, or Ae. sharonensis was the most likely donor of the B genome. If the B genome in the polyploid wheats is monophyletic in origin, the collective findings of this and other investigations indicate that Ae. searsii is the most likely donor. The possibility that the B genome in the polyploid wheats could have a polyphyletic origin is also discussed.Key words: polyploid wheats, putative B-genome donors, purothionins, monophyletic, polyphyletic.
Genomic relationships of Triticum searsii to other S-genome diploid Triticum species
Authors: Yen Yang , Kimber Gordon
Published: April 2011

Interspecific triploid hybrids of Triticum searsii (2x) (= Aegilops searsii) with T. longissimum (4x), T. speltoides (4x), and T. bicorne (4x) were made and cytologically studied. Optimization analyses of the meiotic configurations allow the calculation of a numerical measure (the natural logarithm of the ratio of the relative affinity of the most closely related chromosomes to the most distantly) of phylogenetic distance and showed that T. searsii was almost equally but distantly related to the three other species. The validity of T. searsii being a biological species is therefore confirmed.Key words: triploid, wheat, meiosis, phylogenesis, hybrid.
D-genome suppression of gliadin electrophoretic band 45 in hexaploid wheat and the effect upon quality
Authors: Howes N. K. , Kovacs M. I. , Kerber E. R.
Published: April 2011

The hexaploid wheat 'Prelude' (2n = 42 = AABBDD) contains the endosperm protein electrophoretic band 40, but not band 45, while the extracted tetraploid 'Tetraprelude' (2n = 28 = AABB) contains electrophoretic band 45 but not band 40. Moreover, F3 progeny from the cross between backcross lines of 'Prelude' and 'Marquis' segregated as if both of these proteins were controlled by alleles of one gene, or by two very closely linked genes. Examination of the F3 seed from the cross 'Prelude' × 'Canthatch' 7D nullisomic showed that band 45 was not expressed in any of the 334 F2 families, including nine nullisomics. Together, these results indicate that band 45 endosperm protein is not suppressed by a gene on chromosome 7D. Furthermore, removal of the D genome from 'Prelude' resulted in increased kernel hardness and increased gluten elastic strength but a decrease in sodium dodecyl sulfate sedimentation volume. However, the sodium dodecyl sulfate sedimentation volume of 'Tetraprelude', was the highest among the tetraploid cultivars evaluated.Key words: wheat, sodium dodecyl sulfate electrophoresis, endosperm protein, gene expression.
In situ localization of a mammalian protamine gene: parameters affecting specificity of hybridization
Authors: Krawetz Stephen A. , Herfort Manfred H. , Dixon Gordon H.
Published: April 2011

Southern hybridization analysis of Indian muntjac genomic DNA with the Eco-Taq bovine genomic protamine probe revealed a simple banding pattern. The pattern of hybridization was identical with that previously observed in the genus Bos. This suggested that the bovine probe specifically hybridized to the Indian muntjac protamine gene. The opportunity was thus provided to assign the chromosomal location of the protamine gene in a comparatively simple system. Accordingly, this probe and the corresponding cDNA probe were used for in situ chromosome hybridization and localization. Various parameters affecting specificity and the resolution of hybridization were examined. Subsequent to optimization, the Indian muntjac gene was shown to be autosomal and distally located in the telomeric region of the p arm of chromosome 1.Key words: chromosomal localization, muntjac, protamine, specificity, hybridization.
Organization of the 5S rRNA genes in the soybean Glycine max (L.) Merrill and conservation of the 5S rDNA repeat structure in higher plants
Authors: Gottlob-McHugh S. G. , Lévesque M. , MacKenzie K. , Olson M. , Yarosh O. , Johnson D. A.
Published: April 2011

The 5S rRNA gene of the soybean Glycine max (L.) Merr. has been cloned on a 556-bp fragment of DNA and sequenced. This fragment contains two copies of the soybean 5S rDNA sequence, one intact and one truncated, separated by noncoding DNA. We have used this clone to investigate the organization of the 5S genes within the soybean genome and the extent of their methylation. Our results demonstrate that soybean 5S genes are clustered, organized into tandem repeats of 330 bp, and extensively methylated. Hybridization of the 5S sequence to Southern transfers of soybean DNA digested with BamHI reveals a striking ladderlike pattern. Hybridization of the soybean 5S sequence to a wide variety of plant DNAs results in similar patterns, suggesting that the 5S rDNA sequence, gene organization, and methylation pattern are conserved in many higher plants.Key words: 5S rDNA, sequence, methylation, soybean, repeat conservation.
Chromosomal location of genes for supernumerary spikelet in tetraploid wheat
Authors: Klindworth D. L. , Williams N. D. , Joppa L. R.
Published: April 2011

The supernumerary spikelet (SS) trait of durum wheat (Triticum turgidum L.), including the ramified and four-rowed spike traits, is characterized by an increased number of spikelets per spike. Chromosomal location of the SS gene(s) was determined by crossing the ramified spike line PI349056 to the set of 'Langdon' D-genome disomic substitution lines. Double monosomic F1 plants were backcrossed to PI349056 and the testcross F1 plants were classified for chromosome pairing and spike type. Segregation for spike type was observed in the testcross F2. Data indicated that the major SS gene was located on chromosome 2A. Subsequent crosses with the 'Langdon' 2A telosomics indicated that the major SS gene was located on the short arm of chromosome 2A. Segregation of the testcross F2 indicated that a minor SS gene was located on chromosome 2B. Results also indicated that inhibitors of SS may be located on the D-genome chromosomes and an additional experiment was designed to test this hypothesis. Eight D-genome monosomic addition lines were developed by backcrossing PI349056 from one to three times to plants containing D-genome univalents. The test populations contained two cytological types of plants, disomics having 14 pairs of durum chromosomes and D-genome monosomic additions having 14 pairs of durum chromosomes plus a D-genome monosome. Comparison of these two types of plants indicated that chromosome 2D (from 'Chinese Spring' wheat) had a strong inhibitor of SS expression.Key words: Triticum, branched spike, ramified spike, four-rowed spike, cytogenetics.
Reinvestigation of the S genome in Triticum kotschyi
Authors: Yen Yang , Kimber Gordon
Published: April 2011

Hybrids of Triticum kotschyi with induced autotetraploids of Triticum longissimum, Triticum speltoides, and Triticum bicorne and diploid T. speltoides were obtained. This is the first report of successful hybridization between T. kotschyi and T. bicorne. Optimizing meiotic data showed that the tetraploid hybrid involving T. longissimum (4x) fit the 3:1 model best with an x-value of 1.000, while those involving T. speltoides (4x) and T. bicorne (4x) fit the 2:2 and 2:1:1 models best with an x-value of 0.744 and 0.989, respectively. The triploid hybrid of T. kotschyi × T. speltoides fit the 3:0 model best with an x-value of 0.500. A reciprocal translocation was observed between T. kotschyi and T. speltoides. It is suggested that T. longissimum is the possible donor species of the S genome to T. kotschyi and that this S genome has remained essentially unchanged since its incorporation. This and other evidence suggest that T. kotschyi likely originated from the hybridization of T. longissimum × T. umbellulatum.Key words: hybrid, meiosis, chromosome pairing, autotetraploid, phylogenesis.
Genotype-dependent interchromosomal effects of a grasshopper reciprocal translocation
Authors: Arana P. , Henriques-Gil N. , Santos J. L.
Published: April 2011

The existence of interchromosomal effects has been tested in four segregating families of the grasshopper Eyprepocnemis plorans carrying the same translocation. The comparisons between the mean chiasma frequencies in the translocation heterozygotes and the standard homozygotes have revealed different responses, depending on the family: both significant increases and decreases in those bivalents not involved in the translocation have been found. A dependence of interchromosomal effects on genetic background is suggested.Key words: translocation, chiasma frequency, interchromosomal effect.
An interspecific hybrid and amphiploid produced from Triticum aestivum crosses with Agropyron cristatum and Agropyron desertorum
Authors: Limin A. E. , Fowler D. B.
Published: April 2011

Agropyron cristatum L. Gaertner (2n = 14) and Agropyron desertorum (Fisch. ex Link) Schultes (2n = 28) cultivars were crossed with common wheat (Triticum aestivum L. em. Thell. 2n = 42, ABD genomes) in an attempt to bring the P genome of Agropyron into a wheat background for future genetic exploitation and to evaluate possible homoeology with the wheat genomes. Interspecific hybrid plants were obtained from crosses using both Agropyron species. Chromosome doubled amphiploids (2n = 56, AABBDDPP) were successfully produced by colchicine treatment of hybrid plants from the T. aestivum – A. cristatum cross. Meiotic cells of the amphiploid contained the expected 28 chromosome pairs but also exhibited a considerable amount of chromosome pairing disturbance, resulting in an average of 3.55 univalents per cell. Consequently, fertility was reduced in the amphiploid and the progeny were frequently aneuploid. Homoeologous pairing in the T. aestivum – A. cristatum hybrid was low, but the pairing disruption exhibited in the amphiploid suggested that homoeologous relationships may have been masked in the hybrid.Key words: Triticum aestivum, Agropyron cristatum, chiasma frequency, intergeneric hybrid, amphiploid.
Cytogenetic studies in the genus Chaetobromus (Poaceae: Arundineae)
Authors: Spies J. J. , Plessis H. Du , Barker N. P. , Wyk S. M. C. Van
Published: April 2011

The genus Chaetobromus consists of four, somewhat ill defined species. Morphological merging and the existence of intermediates render the separation of these species difficult. A basic chromosome number of x = 6 for Chaetobromus is substantiated by the presence of diploid specimens. The genus forms a polyploid complex, ranging from diploid to duodecaploid. Polyploidy occurs in the form of segmental alloploidy and occasionally as alloploidy. Meiotic abnormalities, in the form of univalents during metaphase I and anaphase laggards, were observed in some specimens. A cancerous growth form, involving the merging of different cells and the subsequent fusion of their nuclei, has been observed in two specimens, Spies 3366 and CW1. No apparent explanation could be found for this uncontrolled increase in ploidy level during microsporogenesis. Extensive morphological, anatomical, and cytogenetical variation exists in the genus, indicating hybridization and polyploidization. Numerical analysis of morphological data obtained from the specimens studied indicates two groups. Cytogenetic evidence supports the numerical analysis. In an attempt to resolve the contributor species to this polyploid hybrid swarm, attention should be given to the diploid representatives of the putative progenitor species.Key words: Chaetobromus, hybridization, meiosis, numerical taxonomy, polyploidy.
B-chromosome and C-band heterochromatin variation in Arizona maize populations adapted to different altitudes
Authors: Porter H. L. , Rayburn A. Lane
Published: April 2011

The B-chromosome and C-band numbers were determined in 12 Arizona Indian maize populations. These populations were originally collected from altitudes ranging from 100 to 5300 ft (1 ft = 0.3048 m). In addition, the total nuclear DNA amounts of these populations have been observed to vary by as much as 20%. The number of B-chromosomes was not significantly correlated with altitude, C-band number, or nuclear DNA amount. C-band number was significantly correlated with both altitude and genome size. It does not appear that the amount of C-band variation can account for the large nuclear DNA variation observed in these accessions. Additional A-chromosomal DNA sequences may be involved in the nuclear DNA content variation that exists among these accessions.Key words: heterochromatin, DNA content, evolution, repeated DNA.
Intergeneric hybrids between Triticum aestivum and three crested wheatgrasses: Agropyron mongolicum, A. michnoi, and A. desertorum
Authors: Chen Qin , Jahier Joseph , Cauderon Yvonne
Published: April 2011

Three hybridizations of Triticum aestivum cv. Chinese Spring (CS) (2n = 42) with Agropyron mongolicum (2n = 14), A. michnoi (2n = 28), and A. desertorum (2n = 28) are reported for the first time. Hybrid embryos were obtained at frequencies of 0.24, 1.13, and 2.05%, respectively. The hybrid plants obtained from pollinating CS by A. mongolicum had the expected chromosome number of 2n = 4x = 28, but as a result of hybrid necrosis, none could be raised to the adult stage. Hybrids CS × A. michnoi and CS × A. desertorum both had 2n = 5x = 35 chromosomes. The average meiotic chromosome pairing per cell was 7.04 I + 12.14 II + 1.06 III + 0.07 IV + 0.02 V + 0.02 VI and 9.29 I + 11.05 II + 1.14 III + 0.05 IV, respectively. Their analysis leads to the conclusions that (i) the two Agropyron genomes in the hybrids share a high degree of homology, thus revealing that tetraploid Agropyron species are true autoploids (genome constitution PPPP) and (ii) gene(s) in the Agropyron species suppress the activity of the homoeologous pairing control system of wheat. The possibility of gene transfer from Agropyron to wheat is discussed.Key words: intergeneric hybrids, Triticum aestivum, Agropyron species, hybrid necrosis, chromosome pairing.
Cytology and taxonomy of Elymus kengii, E. grandiglumis, E. alatavicus, and E. batalinii (Poaceae: Triticeae)
Authors: Jensen Kevin B.
Published: April 2011

Elymus alatavicus (Drob.) A. Löve, E. batalinii (Krasn.) A. Löve, E. kengii (Keng) Tzvelev, and E. grandiglumis (Keng) A. Löve are rare hexaploid perennial grasses of the tribe Triticeae native to central Asia. This paper further describes the (i) genomic makeup of E. batalinii and E. alatavicus; (ii) chromosome pairing and fertility in hybrids between E. alatavicus or E. batalinii and E. kengii or E. grandiglumis; (iii) morphological variation among the taxa; and (iv) necessary taxonomic changes within Elymus necessitated by the above studies. On the basis of chromosome pairing in the hybrids E. batalinii × E. dentatus (Hook. f.) Tzvelev ssp. ugamicus (Drob.) Tzvelev, 10.21 I + 12.11 II + 0.18 III + 0.01 IV, and E. alatavicus × Pseudoroegneria tauri (Boiss. &Bal.) A. Löve, 13.10 I + 10.05 II + 0.52 III + 0.08 IV, the genomic formula for E. batalinii and E. alatavicus can be written as SSYYPP. Chromosome pairing in the hybrids E. alatavicus × E. grandiglumis, 9.37 I + 16.23 II + 0.06 III; E. kengii × E. batalinii, 10.25 I + 15.54 II + 0.21 III + 0.02 IV; and E. grandiglumis × E. batalinii, 9.15 I + 13.47 II + 1.09 III + 0.06 IV, combined with species morphology, supports the grouping of the above taxa in Elymus L. section Hyalolepis (Nevski) A. Löve rather than being separated in Elymus section Goulardia (Husnot) Tzvelev.Key words: genome, meiosis, chromosome pairing, interspecific hybrids, Elymus, Triticeae.
Isochromosome Y in an infertile heifer
Authors: Pinheiro L. E. L. , Mikich A. B. , Bechara G. H. , Almeida I. L. , Basrur P. K.
Published: April 2011

The chromosome makeup of a 3-year-old crossbred heifer was examined in an attempt to explore the cytogenetic causes of her infertility. The heifer proved to be a mosaic carrying predominantly XY cells and with approximately 30% of cells lacking a normal Y. The minor population included cells carrying a dicentric isochromosome Y and a small proportion of XO cells. Histological features of the gonads and reproductive system suggest that the presence of cells resulting from isochromosome formation and the consequent loss of the Y chromosome segment required for testicular induction may have been causally related to the embryonic state of the gonads and malformation of the duct system noted in this heifer.Key words: isochromosome, infertility, isodicentric Y, gonadal dysgenesis, chromosome mosaicism.
1R chromosome nucleolus organizer region activation by 5-azacytidine in wheat × rye hybrids
Authors: Vieira Rita , Queiroz Álvaro , Morais Leonor , Barão Augusta , Mello-Sampayo T. , Viegas Wanda S.
Published: April 2011

Nucleolar activity was studied in several lines of Triticum aestivum cv. Chinese Spring, Triticum turgidum cv. Durum, and F1 hybrids from euploid and aneuploid lines of T. aestivum and Secale cereale cv. Centeio do Alto, in cells from root tips of seeds germinated in water or in 5-azacytidine. 5-Azacytidine, an analog of cytidine modified in the 5 position of the pyrimidine ring, inhibits DNA methylation. By using silver staining to determine the number of nucleolus organizer regions and the average number of nucleoli per root-tip cell from seeds germinated in both situations, it became apparent that the presence of 5-azacytidine during germination allowed for the expression of the nucleolus organizer region locus belonging to the rye genome, in contrast to the usual observed cytological absence of the rye nucleolus organizer region in wheat–rye hybrids. It is suggested that wheat nucleolar dominance in wheat–rye hybrids is mainly a consequence of methylation of rRNA genes or its regulators located on the 1R chromosome of rye.Key words: 1R nucleolar organizer, wheat–rye hybrids, methylation, Ag-NOR.
Homology of chromosomes of Triticum macha Dek. et Men. and Triticum aestivum L. as shown with the help of genetic markers
Authors: Metakovsky E. V. , Iakobashvili Z. A.
Published: April 2011

Inheritance of the storage protein (gliadin and glutenin) genes of Triticum macha Dek. et Men. and their allelism to Triticum aestivum L. genes have been studied. A close homology of at least chromosomes 1A and 1B of the two species has been found. Results confirm a very close relationship between T. macha and T. aestivum.Key words: seed storage proteins, genetic analysis, chromosome homology, relationship of Triticum macha Dek. et Men. and Triticum aestivum L.
Karyotypic analyses of four species of Ambystoma (Amphibia, Caudata) that have been implicated in the production of all-female hybrids
Authors: Taylor Alison S. , Bogart James P.
Published: April 2011

Four salamander species of the genus Ambystoma hybridize in the Great Lakes region of eastern North America. The hybrids are mostly polyploid and virtually all-female. Basic chromosomal morphology and C-banding patterns of Ambystoma laterale, A. jeffersonianum, A. texanum, and A. tigrinum tigrinum were examined in an attempt to find some markers that would be useful to recognize genomic constitution of the hybrids. Several minor morphological differences were found among the karyotypes of the four species, but none were of sufficient magnitude to unambiguously assign genomic content in a hybrid. There was no evidence of sexually dimorphic bands in any of the species.Key words: chromosomes, Ambystoma, C-bands, hybridization, amphibia.
Phenotypic consequences of copper-zinc superoxide dismutase overexpression in Drosophila melanogaster
Authors: Staveley Brian E. , Phillips John P. , Hilliker Arthur J.
Published: April 2011

We report here the isolation of a tandem duplication of a small region of the third chomosome of Drosophila melanogaster containing the Cu–Zn superoxide dismutase (cSOD) gene. This duplication is associated with a dosage-dependent increase in cSOD activity. The biological consequences of hypermorphic levels of cSOD in genotypes carrying this duplication have been investigated under diverse conditions of oxygen stress imposed by acute exposure to ionizing radiation, chronic exposure to paraquat, and the normoxia of standard laboratory culture. We find that a 50% increase in cSOD activity above the normal diploid level confers increased resistance to ionizing radiation and, in contrast, confers decreased resistance to the superoxide-generating agent paraquat. The duplication is associated with a minor increase in adult life-span under conditions of normoxia. These results reveal important features of the biological function of cSOD within the context of the overall oxygen defense system of Drosophila.Key words: gene duplication, paraquat, ionizing radiation, life-span.
Synaptonemal complex analysis of mole rats (Spalax ehrenbergi): unusual polymorphisms of chromosome
Authors: Greenbaum Ira F. , Hale David W. , Sudman Philip D. , Nevo Eviatar
Published: April 2011

Two unusual structural polymorphisms in the largest chromosomal pair of the Israeli mole rat, Spalax ehrenbergi, were analyzed from surface-spread and silver-stained preparations of synaptonemal complexes. A C-band negative polymorphism for the length of the 1p arm was visible as axial length differences during late zygonema and early pachynema. This region underwent synaptic adjustment resulting in a fully paired, mid-pachytene synaptonemal complex with equalized axial lengths. The somatically variable and nonargentophilic secondary constriction in the 1q arm was evident as a distinct silver-stained thickening along the synaptonemal complex. Presence of this structure on the synaptonemal complex varied both among individuals and among cells within individuals. The intraindividual variation of this region is hypothesized to represent differential biochemical activity with its cellular visualization being regulated in a manner similar to that of nucleolus organizer regions.Key words: mole rats, synaptonemal complex, chromosomal polymorphism.
Analysis of synaptonemal complexes in the amphidiploid of Lolium multiflorum × Festuca drymeja
Authors: Thomas Huw M.
Published: April 2011

Synaptonemal complexes in the amphidiploid Lolium multiflorum (4χ) × Festuca drymeja (4χ) have been examined by the whole mount spreading technique in nuclei with between 49 and 100% pairing. At mid to late zygotene nonhomologous associations are formed, with multivalents involving more than half the total axial element length in some cases. However, they are corrected by pachytene. There is evidence of differences in the timing or rate of pairing between the two sets of chromosomes; the L. multiflorum chromosomes seem more advanced than the F. drymeja chromosomes in their pairing at mid and late zygotene, and it is possible that this asynchrony places a constraint on intergenomic chromosome pairing.Key words: Lolium-Festuca, amphidiploid, synaptonemal complexes, nonhomologous pairing, correction mechanism.
Dilemma of genome relationship in the diploid species Thinopyrum bessarabicum and Thinopyrum elongatum (Triticeae: Poaceae)
Authors: Jauhar Prem P.
Published: April 2011

Evidence on the relationship of the J genome of diploid Thinopyrum bessarabicum and the E genome of diploid Thinopyrum elongatum (= Lophopyrum elongatum) is discussed. Low chromosome pairing between J and E at different ploidy levels, suppression of J–E pairing by the Ph1 pairing regulator that inhibits homoeologous pairing, complete sterility of the diploid hybrids (JE), karyotypic differentiation of the two genomes and differences in their biochemical organization as reflected in total content and distribution of constitutive heterochromatin, and marked differences in isozymes, 5S DNA, and rDNA indicate that J and E are distinct genomes. These genomes are homoeologous and not homologous. There is no justification for the merger of J and E genomes.Key words: chromosome pairing, Ph1 pairing regulator, C-banding, isozymes, 5S DNA, rDNA.
An in vitro chromosome doubling method for clovers (Trifolium spp.)
Authors: Anderson J. A. , Mousset-Déclas C. , Williams E. G. , Taylor N. L.
Published: April 2011

This research reports a new technique for chromosome doubling of clover (Trifolium sp.) axillary meristems via in vitro colchicine application. Plant material utilized included T. pratense (red clover) cv. Kenstar clones, and three interspecific hybrids: T. ambiguum (kura clover) × T. repens (white clover); T. alpestre × T. pratense; and T. sarosiense × T. pratense. Vegetative axillary meristems were excised from plants, surface sterilized, and trimmed to a length of 0.5–1 mm. Meristems were placed on the surface of a shoot proliferation medium (ML8) containing colchicine (0.1%) for 48 or 72 h and then transferred back to ML8. Alternative treatments were to preculture meristems on ML8 for 7 days prior to colchicine treatment. Plantlets with two or three trifoliolate leaves were induced to root on CR2 or RL rooting media. Preculturing of meristems on ML8 prior to colchicine exposure resulted in the highest chromosome doubling frequencies among the different genotypes, although there was apparent genotype × treatment interaction. Chromosome doubling frequencies were as high as 81 and 44% for initial root tips and mature shoots, respectively. To make rapid assessments of ploidy level of flowering plants, pollen shape was examined. Chromosome doubling increased the pollen stainability of the T. ambiguum × T. repens hybrid from 2.5 to 33.6%, but did not result in fertility in the other two interspecific hybrids.Key words: Trifolium, colchicine, chromosome doubling, interspecific hybrids.
Meiotic chromosome structure. Kinetochores and chromatid cores in standard and B chromosomes of Arcyptera fusca (Orthoptera) revealed by silver staining
Authors: Suja J. A. , de la Torre J. , Giménez-Abián J. F. , Vega C. García de la , Rufas J. S.
Published: April 2011

The behaviour of two chromosome structures in silver-stained chromosomes was analyzed through the first meiotic division in spermatocytes of the acridoid species Arcyptera fusca. Results showed that at diakinesis kinetochores and chromatid cores are individualized while they associate in bivalents of metaphase I; only kinetochores and distal core spots associate in the sex chromosome. Metaphase I is characterized by morphological and localization changes of both kinetochores and cores which define the onset of anaphase I. These changes analyzed in both autosomes and in the sex chromosome allow us to distinguish among three different substages in metaphase I spermatocytes. B chromosomes may be present as univalents, bivalents, or trivalents. Metaphase I B univalents are characterized by separated cores except at their distal ends and individualized and flat sister kinetochores. At anaphase I sister kinetochores of lagging B chromatids remain connected through a silver-stained strand. The behaviour of cores and kinetochores of B bivalents is identical with that found in the autosomal bivalents. The differences in the morphology of kinetochores of every chromosome shown by B trivalents at metaphase I may be related to the balanced forces acting on the multivalent. The results show dramatic changes in chromosome organization of bivalents during metaphase I. These changes suggest that chromatid cores are not involved in the maintenance of bivalents. Moreover, the changes in morphology of kinetochores are independent of the stage of meiosis but correlate with the kind of division (amphitelic–syntelic) that chromosomes undergo.Key words: kinetochore, chromatid core, B chromosomes, meiosis, chromosome structure, silver staining.
The chromosomal location of genes encoding NADH dehydrogenase isozymes in hexaploid wheat and related species
Authors: Liu C. J. , Gale M. D.
Published: April 2011

Analysis of NADH dehydrogenase isozymes in hexaploid wheat (Triticum aestivum) by flat-bed isoelectric focusing revealed a genetic system involving four sets of Ndh loci. The Ndh-A1 locus, previously identified on chromosome arm 4AL, was confirmed. Homoeoloci Ndh-R1 in rye, Ndh-H1 in barley, Ndh-Hch1 in Hordeum chilense, Ndh-Sl1 in Aegilops sharonensis, and Ndh-V1 in Dasypyrum villosum were also identified. The Ndh-2 loci, encoding monomeric isozymes, were found in the short arms of homoeologous group 7 chromosomes. Homoeoloci Ndh-A2, Ndh-D2, and Ndh-R2 are described. The Ndh-3 set, encoding multimeric isozymes, were found on each of the homoeologous group 3 chromosome long arms. An Ndh-B3b variant and homoeoloci Ndh-R3 (on chromosome arm 6RL), Ndh-H3, and Ndh-Sl3 are described. The Ndh-4 set, encoding monomeric isozymes for which no varietal variation was found, were identified on the short arms of group 3 chromosomes. Ndh-A4, Ndh-B4, Ndh-H4, Ndh-R4, and Ndh-E4 (Agropyron elongatum) homoeoloci are described.Key words: NADH dehydrogenase, isozymes, wheat, Triticeae.
Meiotic pairing control in wheat–rye hybrids. II. Effect of rye genome and rye B-chromosomes and interaction with the wheat genetic system
Authors: Cuadrado C. , Romero C. , Lacadena J. R.
Published: April 2011

Several hybrid combinations between rye and wheat ditelosomic for homoeologous group 3 or 5 chromosomes or mutant ph2b were used to analyze the effects of the rye genome and rye B-chromosomes on meiotic pairing. The results indicated that the rye Bs have an effect on bound-arm frequency, which varies with the wheat genotype. If wheat suppressors are absent, pairing decreases when Bs are added; whereas if wheat promoters are lacking, a pairing increase is observed in some hybrids with two rye Bs. There was thus an interaction between the genetic systems of the two parents, with the wheat parent being the main determinant of the pairing level in the hybrids. The rye genome tends to decrease pairing in the absence of wheat suppressors and increase it when wheat promoters are lacking, and the rye Bs tend to reinforce this primary rye action.Key words: Triticum aestivum, Secale cereale, homoeologous pairing, B-chromosomes, promoter–suppressor interaction.
A DNA polymorphism from five inbred strains of the mouse identifies a functional class of domesticus-type Y chromosome that produces the same phenotypic distribution of gonadal hermaphrodites
Authors: Biddle Fred G. , Eales Brenda A. , Nishioka Yutaka
Published: April 2011

The wild-derived CLA inbred strain of the house mouse contains a domesticus-type Y chromosome that lacks a 2.3-kb TaqI band with fragment 1 of the AC11 probe. The CLA Y chromosome also causes a low frequency of XY gonadal hermaphrodites when backcrossed to the C57BL/6J strain (F.G. Biddle and Y. Nishioka. 1988. Genome, 30: 870–878). A similar domesticus-type Y chromosome, lacking the 2.3-kb TaqI band has now been found in the four historical inbred strains AKR/J, MA/MyJ, PL/J, and RF/J. When backcrossed to C57BL/6J, these four Y chromosomes cause low frequencies of gonadal hermaphrodites similar to the CLA Y and phenotypic distributions of types of gonad are indistinguishable from that with the CLA Y. The absence of the 2.3-kb TaqI band appears to be a polymorphism among domesticus-type Y chromosomes that identifies one of the three functional classes that, so far, can be distinguished only by their effects on testis differentiation in backcross test fetuses with the C57BL/6J strain. Three other historical inbred strains, BUB/BnJ, ST/bJ, and SWR/J, with a domesticus-type Y chromosome but containing the 2.3-kb TaqI band, were also assayed. They permit normal testis development in backcross test fetuses with C57BL/6J.Key words: mouse, Y chromosome, gonadal hermaphrodites, primary sex determination.
Karyotype studies on Pisum fulvum and Pisum sativum, using a chromosome image analysis system
Authors: Errico A. , Conicella C. , Venora G.
Published: April 2011

Karyotype studies were conducted on Pisum fulvum, employing traditional and image analysis methods. Meiotic data from F1 plants obtained from crosses between Pisum sativum and P. fulvum were also obtained and correlated with the karyotype data. The karyotypes of the wild species P. fulvum were different from the standard P. sativum karyotype for relative length and arm ratio of chromosomes III, V, and VII; an additional satellite is present in chromosome V and a longer satellite in chromosome VII. These chromosome differences resulted from two independent reciprocal interchanges, T(3–5) and T(1–7), which were determined by meiotic analysis of crosses made to translocation tester stocks.Key words: translocation, computer system, Pisum, karyotype.