bluuebunny/crossref_metadata_2025 huggingface dataset:
Isolation and characterization of a gene encoding a drought-induced cysteine protease in tomato (Lycopersicon esculentum)
Authors: Harrak Hassan , Azelmat Souad , Baker Edward N , Tabaeizadeh Zohreh
Published: April 2011

In a previous study, a 65 kDa protein, TDI-65, was found to be accumulated in the leaves of drought-stressed tomato (Lycopersicon esculentum cv. Starfire) plants. The protein level returns to control level when the drought-stressed plants are rewatered. Antibodies raised against the purified protein were used to elucidate the subcellular localization of the protein. The protein was found to be mainly localized in the nuclei and chloroplasts of drought-stressed leaf cells. To identify the nature of the protein, a cDNA library was constructed and screened by the purified anti-TDI-65 antibody. A cDNA clone designated tdi-65 was isolated and characterized. The deduced amino acid sequences of tdi-65 protein has extensive homology with known cysteine proteases such as actinidin and papain. Northern blot analysis revealed that tdi-65 mRNA is 10-fold higher in drought-stressed plants as compared to control and rewatered plants. Similar results were observed in the tomato cultivar Ailsa and its near isogenic abscisic acid (ABA)-deficient mutant line, flacca, suggesting that the gene does not require ABA for its expression under drought conditions. Based on the previous immunolocalization findings we suggest that tdi-65 encoded cysteine protease functions in relation to drought-induced senescence and programmed cell death.Key words: abscisic acid, cysteine protease, drought, programmed cell death, senescence, tomato.
Instability of bacterial artificial chromosome (BAC) clones containing tandemly repeated DNA sequences
Authors: Song Junqi , Dong Fenggao , Lilly Jason W , Stupar Robert M , Jiang Jiming
Published: April 2011

The cloning and propagation of large DNA fragments as bacterial artificial chromosomes (BACs) has become a valuable technique in genome research. BAC clones are highly stable in the host, Escherichia coli, a major advantage over yeast artificial chromosomes (YACs) in which recombination-induced instability is a major drawback. Here we report that BAC clones containing tandemly repeated DNA elements are not stable and can undergo drastic deletions during routine library maintenance and DNA preparation. Instability was observed in three BAC clones from sorghum, rice, and potato, each containing distinct tandem repeats. As many as 46% and 74% of the single colonies derived from a rice BAC clone containing 5S ribosomal RNA genes had insert deletions after 24 and 120 h of growth, respectively. We also demonstrated that BAC insert rearrangement can occur in the early stage of library construction and duplication. Thus, a minimum growth approach may not avoid the instability problem of such clones. The impact of BAC instability on genome research is discussed.Key words: repetitive DNA, large insert DNA library, genome research.
Nuclear DNA content and base composition in 28 taxa of Musa
Authors: Kamaté K , Brown S , Durand P , Bureau J -M , Nay D De , Trinh T H
Published: April 2011

The nuclear DNA content of 28 taxa of Musa was assessed by flow cytometry, using line PxPC6 of Petunia hybrida as an internal standard. The 2C DNA value of Musa balbisiana (BB genome) was 1.16 pg, whereas Musa acuminata (AA genome) had an average 2C DNA value of 1.27 pg, with a difference of 11% between its subspecies. The two haploid (1C) genomes, A and B, comprising most of the edible bananas, are therefore of similar size, 0.63 pg (610 million bp) and 0.58 pg (560 million bp), respectively. The genome of diploid Musa is thus threefold that of Arabidopsis thaliana. The genome sizes in a set of triploid Musa cultivars or clones were quite different, with 2C DNA values ranging from 1.61 to 2.23 pg. Likewise, the genome sizes of tetraploid cultivars ranged from 1.94 to 2.37 pg (2C). Apparently, tetraploids (for instance, accession I.C.2) can have a genome size that falls within the range of triploid genome sizes, and vice versa (as in the case of accession Simili Radjah). The 2C values estimated for organs such as leaf, leaf sheath, rhizome, and flower were consistent, whereas root material gave atypical results, owing to browning. The genomic base composition of these Musa taxa had a median value of 40.8% GC (SD = 0.43%).Key words: Musa, cytometry, banana.
Antisense inhibition of a tomato meiotic proteinase suggests functional redundancy of proteinases during microsporogenesis
Authors: Riggs C Daniel , Zeman Katherine , DeGuzman Rhoda , Rzepczyk Annette , Taylor Andrew A
Published: April 2011

Anther development in angiosperms culminates in the programmed cell death of specific tissues to facilitate the release of pollen. Despite a wealth of morphological descriptions of this process, there have been few reports on the regulation of dehiscence or the coordination of events between tissues. We have cloned an anther-specific tomato gene encoding a serine proteinase that is expressed during meiosis and late microsporogenesis. The conceptualized tomato meiotic proteinase (TMP) is a member of a family of genes that exhibit characteristics of mammalian proprotein convertases. To examine the role of TMP in microsporogenesis, we generated transgenic plants harboring an antisense construct of the gene. Some of these plants produced little or no detectable TMP, yet no phenotypic abnormalities were observed. Zymogram analyses revealed that multiple proteinases are present in mature anthers and that proteinase activity increases as development proceeds. Taken together, these data indicate that the role of TMP during microsporogenesis, if any, may be compensated for by other proteinases.Key words: anther, development, pollen, proteinase, subtilase, tapetum.
Karyotype analysis ofLilium longiflorumandLilium rubellumby chromosome banding and fluorescence in situ hybridisation
Authors: Lim Ki-Byung , Wennekes Jannie , Jong J Hans de , Jacobsen Evert , van Tuyl Jaap M
Published: April 2011

Detailed karyotypes of Lilium longiflorum and L. rubellum were constructed on the basis of chromosome arm lengths, C-banding, AgNO3staining, and PI-DAPI banding, together with fluorescence in situ hybridisation (FISH) with the 5S and 45S rDNA sequences as probes. The C-banding patterns that were obtained with the standard BSG technique revealed only few minor bands on heterologous positions of the L. longiflorum and L. rubellum chromosomes. FISH of the 5S and 45S rDNA probes on L. longiflorum metaphase complements showed overlapping signals at proximal positions of the short arms of chromosomes 4 and 7, a single 5S rDNA signal on the secondary constriction of chromosome 3, and one 45S rDNA signal adjacent to the 5S rDNA signal on the subdistal part of the long arm of chromosome 3. In L. rubellum, we observed co-localisation of the 5S and 45S rDNA sequences on the short arm of chromosomes 2 and 4 and on the long arms of chromosomes 2 and 3, and two adjacent bands on chromosome 12. Silver staining (Ag-NOR) of the nucleoli and NORs in L. longiflorum and L. rubellum yielded a highly variable number of signals in interphase nuclei and only a few faint silver deposits on the NORs of mitotic metaphase chromosomes. In preparations stained with PI and DAPI, we observed both red- and blue-fluorescing bands at different positions on the L. longiflorum and L. rubellum chromosomes. The red-fluorescing or so-called reverse PI-DAPI bands always coincided with rDNA sites, whereas the blue-fluorescing DAPI bands corresponded to C-bands. Based on these techniques, we could identify most of chromosomes of the L. longiflorum and L. rubellum karyotypes.Key words: fluorescence in situ hybridisation, FISH, 5S rDNA, 45S rDNA, C-banding, reverse PI-DAPI banding.
Organization of 5S rDNA in species of the fishLeporinus: two different genomic locations are characterized by distinct nontranscribed spacers
Authors: Martins Cesar , Galetti Jr. Pedro Manoel
Published: April 2011

To address understanding the organization of the 5S rRNA multigene family in the fish genome, the nucleotide sequence and organization array of 5S rDNA were investigated in the genus Leporinus, a representative freshwater fish group of South American fauna. PCR, subgenomic library screening, genomic blotting, fluorescence in situ hybridization, and DNA sequencing were employed in this study. Two arrays of 5S rDNA were identified for all species investigated, one consisting of monomeric repeat units of around 200 bp and another one with monomers of 900 bp. These 5S rDNA arrays were characterized by distinct NTS sequences (designated NTS-I and NTS-II for the 200- and 900-bp monomers, respectively); however, their coding sequences were nearly identical. The 5S rRNA genes were clustered in two chromosome loci, a major one corresponding to the NTS-I sites and a minor one corresponding to the NTS-II sites. The NTS-I sequence was variable among Leporinus spp., whereas the NTS-II was conserved among them and even in the related genus Schizodon. The distinct 5S rDNA arrays might characterize two 5S rRNA gene subfamilies that have been evolving independently in the genome.Key words: 5S rDNA, 5S rRNA gene, nontranscribed spacer, Leporinus, fish.
Heterofertilization exhibited by trifluralin-induced bicellular pollen on diploid and tetraploid maize crosses
Authors: Kato Akio
Published: April 2011

The heterofertilization rates and fertility of trifluralin-induced bicellular pollen were investigated in maize (Zea mays L.). A diploid inbred line, Oh43 (r1/r1), and a tetraploid line, Q28-1 (r1/r1/r1/r1), were pollinated with a trifluralin treated diploid stock heterozygous for R1-scm2. The gene R1-scm2 conditions purple pigmentation in both the embryo and the aleurone layer. Heterofertilized kernels were detected as discordant kernels, i.e., yellow kernel with purple embryo or purple kernel with white embryo. The diploiddiploid crosses treated with 0.20.3% Trefanocide solution (0.090.13% trifluralin) resulted in incidences of discordant kernels (3.74.8%) that were significantly higher than the control (2.3%). Most of the seedlings (86%) of the discordant kernels in the 0.3% treatment were triploids or triploid-class aneuploids. In tetraploiddiploid crosses, trifluralin treatments increased the number of plump kernels on the tetraploid ears. In the 0.3% treatment, 5.2% of ovaries produced plump kernels on the ears and most of the seedlings (92%) were tetraploids or tetraploid-class aneuploids, whereas in the control, only 1.5% ovaries produced plump kernels and most of the seedlings (98%) were triploids or triploid-class aneuploids. A high rate of discordance was observed among the plump kernels both in the treated plots (36.148.0%) and in the control (33.3%). Consequently, almost all of the plump kernels from the tetraploiddiploid crosses were considered to be the results of heterofertilization.Key words: trifluralin-induced bicellular pollen, chromosome doubling, heterofertilization, tetraploiddiploid cross, Zea mays L.
Wheat EST sequence assembly facilitates comparison of gene contents among plant species and discovery of novel genes
Authors: Hattori Jiro , Ouellet Thérèse , Tinker Nicholas A
Published: April 2011

Using a strategy requiring only modest computational resources, wheat expressed sequence tag (EST) sequences from various sources were assembled into contigs and compared with a nonredundant barley sequence assembly, with ESTs, with complete draft genome sequences of rice and Arabidopsis thaliana, and with ESTs from other plant species. These comparisons indicate that (i) wheat sequences available from public sources represent a substantial proportion of the diversity of wheat coding sequences, (ii) prediction of open reading frames in the whole genome sequence improves when supplemented with EST information from other species, (iii) a substantial number of candidates for novel genes that are unique to wheat or related species can be identified, and (iv) a smaller number of genes can be identified that are common to monocots and dicots but absent from Arabidopsis. The sequences in the last group may have been lost from Arabidopsis after descendance from a common ancestor. Examples of potential novel wheat genes and Triticeae-specific genes are presented.Key words: small grain cereal, genome, wheat, barley, bioinformatics.
Origin and evolution ofMytilusmussel satellite DNAs
Authors: Martínez-Lage A , Rodríguez-Fariña F , González-Tizón A , Méndez J
Published: April 2011

A phylogenetic reconstruction based on the amplification of 3 satellite DNAs (stDNAs) was carried out in 1 crustacean species and 15 bivalve species of the subclass Pteriomorphia (10, subfamily Mytilinae; 1, subfamily Litophaginae; 1, subfamily Modiolinae, all belonging to family Mytilidae; 1, family Arcidae; and 2, family Pectinidae). The sequences obtained showed motifs with high similarity to those of A and B boxes of tRNA promoter regions. Dot-blot hybridizations revealed that the 3 stDNAs are present mainly in high copy numbers for each species of the genus Mytilus, whereas for the other species they appear in low copy numbers. Maximum-parsimony trees evidenced a tendency to group Mytilus clones together, and species containing these sequences as a single copy were distributed among the different mytilids. Finally, the possible origin and evolution of these stDNAs is discussed.Key words: bivalves, Pteriomorphia, satellite DNA, phylogeny, dot-blot.
Molecular characterization of the duplicated meristem identity genesHvAP1aandHvAP1bin barley
Authors: Yan Liuling , von Zitzewitz Jarislav , Skinner Jeffrey S , Hayes Patrick M , Dubcovsky Jorge
Published: April 2011

The vernalization gene VRN-1 has been identified as a MADS-box transcription factor orthologous to the meristem identity gene APETALA1 (AP1). A single copy of this gene was found in diploid wheat, but 2 copies were reported in barley. In this study, we present a detailed characterization of these 2 copies to understand their respective roles in the vernalization response. We identified 2 groups of barley bacterial artificial chromosomes (BACs), each containing 1 AP1 copy designated hereafter as HvAP1a and HvAP1b. A physical map of the VRN-H1 region showed that the HvAP1a BACs were part of the VRN-H1 region but that the HvAP1b BACs were not. Numerous structural changes were observed between the barley and wheat VRN-1 physical maps. In a population segregating for VRN-H1, the HvAP1a gene cosegregated with growth habit, suggesting that HvAP1a is the barley vernalization gene VRN-H1. The other copy, HvAP1b, was mapped on the centromeric region of chromosome 1H, the chromosome where vernalization gene VRN-H3 was previously mapped. We developed a mapping population segregating for VRN-H3 and showed that 2 molecular makers flanking HvAP1b locus were not linked to growth habit. The HvAP1b copy has a complete deletion of the first 2 exons, suggesting that it is a truncated pseudogene and not a candidate for VRN-H3. In summary, this study contributed a detailed physical map of the barley VRN-H1 region, showed several structural differences with the orthologous wheat region, and clarified the identity of the barley VRN-H1 gene.Key words: barley, vernalization, Vrn-1, physical map.
Isolation and characterization of the mating-type locus of the barley pathogenPyrenophora teresand frequencies of mating-type idiomorphs within and among fungal populations collected from barley landraces
Authors: Rau Domenico , Maier Frank J , Papa Roberto , Brown Anthony H.D , Balmas Virgilio , Saba Eva , Schaefer Wilhelm , Attene Giovanna
Published: April 2011

Pyrenophora teres f. sp. teres mating-type genes (MAT-1: 1190 bp; MAT-2: 1055 bp) have been identified. Their predicted proteins, measuring 379 and 333 amino acids, respectively, are similar to those of other Pleosporales, such as Pleospora sp., Cochliobolus sp., Alternaria alternata, Leptosphaeria maculans, and Phaeosphaeria nodorum. The structure of the MAT locus is discussed in comparison with those of other fungi. A mating-type PCR assay has also been developed; with this assay we have analyzed 150 isolates that were collected from 6 Sardinian barley landrace populations. Of these, 68 were P. teres f. sp. teres (net form; NF) and 82 were P. teres f. sp. maculata (spot form; SF). Within each mating type, the NF and SF amplification products were of the same length and were highly similar in sequence. The 2 mating types were present in both the NF and the SF populations at the field level, indicating that they have all maintained the potential for sexual reproduction. Despite the 2 forms being sympatric in 5 fields, no intermediate isolates were detected with amplified fragment length polymorphism (AFLP) analysis. These results suggest that the 2 forms are genetically isolated under the field conditions. In all of the samples of P. teres, the ratio of the 2 mating types was consistently in accord with the 1:1 null hypothesis. This ratio is expected when segregation distortion and clonal selection among mating types are absent or asexual reproduction is rare. Overall, sexual reproduction appears to be the major process that equalizes the frequencies of the 2 mating types within populations.Key words: Pyrenophora teres, mating-types, AFLPs, sexual reproduction, selection, barley.
High degree of conservation of nuclear microsatellite loci in the genus Clusia
Authors: Hale M L , Borland A M , Wolff K
Published: April 2011

In plants, microsatellites and their flanking DNA are rarely conserved across a whole genus, let alone other genera in the same family. Therefore, the possibility of using microsatellite primers developed for a species across a large number of plant species in the same genus is often limited. Remarkably, dinucleotide nuclear microsatellites developed for Clusia minor and for Clusia nemorosa amplified homologous microsatellites in species across the whole genus Clusia. In this present study, we report on the DNA sequence variation across the genus of 3 microsatellite loci with varying levels of variation. Compared over the species, there was a correlation between the lengths of the microsatellite loci. Interrupts occurred multiple times and did not seem to lead to the death of the microsatellite. These highly conserved markers will be useful for studying the variable reproductive systems in the genus Clusia.Key words: microsatellite, Clusia, cross-species amplification, microsatellite evolution.
Cytological identification of telotrisomic and double ditelosomic lines in Secale cereale cv. Heines Hellkorn by means of Giemsa C-banding patterns and crosses with wheat–rye addition lines
Authors: Zeller Friedrich J. , Cermeño Mari-Carmen , Friebe Bernd
Published: April 2011

Seven telotrisomic lines (1RS, 1RL, 2RS, 2RL, 3RS acro, 5RS, and 6RS), two double monotelosomic, and two double ditelosomic lines of Secale cereale cv. Heines Hellkorn were analyzed by means of Giemsa C-banding techniques. In crosses with several wheat–rye chromosome addition lines, the telosomic chromosomes in double ditelosomic lines 1/23 and 3/23 were found to be homologous to chromosomes 1R and 2RL of cv. Imperial rye. The C-banding pattern observed for the telosomes in these lines was similar to that detected in the 1R and 2R telosomics of the corresponding telotrisomic lines.

Key words: Secale cereale, telotrisomics, double ditelosomics, C-banding pattern.
Relationships between three measures of genetic distance and breeding behaviour in oats (Avena sativa L.)
Authors: Cowen N. M. , Frey K. J.
Published: April 2011

Nine oat cultivars and experimental lines from four diverse germ plasm sources were crossed in a diallel mating design, without reciprocals. Heterosis for grain yield was evaluated in two experiments and 48 F2-derived lines from each of the 36 matings were evaluated for bundle weight, grain yield, straw yield, harvest index, and heading date in two experiments. The number of transgressive segregates per trait and generalized genetic variances were calculated for each mating. Euclidean distance between parents was calculated by using the first five principal components of the parental correlation matrix. The distance measures of W. D. Hanson and E. Casas (1968. Biometrics, 24: 867–880) and T. S. Cervantes, M. M. Goodman, E. Casas, and J. O. Rawlings (1978. Genetics, 90: 339–348) were calculated for each of two experiments. The relationships between the three distance measures and the three types of breeding behavior were examined via correlation and regression. Euclidean distance was negatively correlated with transgressive segregation and generalized genetic variances. Hanson and Casas' distance measure was positively correlated with transgressive segregation and generalized genetic variances. The distance measure of Cervantes et al. was negatively correlated with heterosis in one experiment. Regressions on the three distances measures, when significant, were linear. The single exception was the regression of heterosis on Euclidean distance, which had significant linear and quadratic coefficients and high R2. No distance measure was closely associated with all three types of breeding behavior. Using information from more than one measure improved the R2 value for polynomial regressions.

Key words: oats, genetic distance, heterosis, generalized variances.
Metaphase I chiasmata in silver-stained cores of bivalents in grasshopper spermatocytes
Authors: Santos J. L. , Ciprés G. , Lacadena J. R.
Published: April 2011

Chiasmata can clearly be observed in proteinaceous scaffold-like structures in condensed metaphase I bivalents of grasshopper spermatocytes by using a highly reproducible silver-staining procedure. Origin and significance of these structures are discussed and the possibility of analyzing several topics related with chiasma formation such as distribution, interference, terminalization, or terminal associations is pointed out.

Key words: scaffold, chiasma, silver staining, terminalization, Chorthippus.
Host–parasite genome relationships in Acridid grasshoppers. I. Variation in the isoenzymes of the Caledia captiva species complex and in the gut bacterium Enterobacter cloacae
Authors: Colgan D. J.
Published: April 2011

Isoenzymic variation was investigated in populations of the four recognized taxa of the Australian acridine Caledia captiva and in 110 isolates of the bacterium Enterobacter cloacae present in their guts. Four types of colony morphology, of which two were common, were discernible in these bacteria. All representatives of each type appeared to be very close to typical members of E. cloacae. The genetic diversity of the eight bacterial enzymes scored was very high, both overall and in respect of the two common morphological types. This diversity is consistent with selective neutrality and is too great to be explained by selective discrimination between genotypes. There was no compelling evidence for any interaction between the host and bacterial genotypes. The results thus argue against the possibility that the parasites are involved in a system of frequency dependent selection. There was also no evidence of an association of bacterial type with divergence between the taxa of the C. captiva complex.

Key words: host–parasite, isoenzymes, grasshoppers, bacteria.
Highly repeated DNA and allozyme variation between sibling species: evidence for introgression
Authors: Arnold M. L. , Wilkinson P. , Shaw D. D. , Marchant A. D. , Contreras N.
Published: April 2011

The Caledia captiva complex of grasshoppers includes two sibling species along with two subspecies. Two populations (Papuan Torresian and Daintree) representing the two sibling species were found to share six allozyme characters and a highly repeated DNA family not found in any of the other Caledia taxa. These two populations showed genic divergence that was equivalent to comparisons between the two subspecies from the complex. Sequenced, cloned repeats from the Papuan Torresian and Daintree taxa showed equivalent variation for both intra- and inter-specific comparisons. A phenetic clustering analysis did not separate the repeats from these two taxa into different clades. Furthermore, the overall genomic organization of the sequence family in the two species is very similar, although the repeats are cytologically dispersed in one form (Papuan Torresian) and clustered in the other form (Daintree). It is argued that the most likely evolutionary explanation for the observed pattern of variation in the allozymes and highly repeated DNA sequences between these types is introgressive hybridization. The possible consequences of such an event are discussed in light of the population genetics and distribution of the present day Caledia taxa.

Key words: highly repeated DNA, Caledia, grasshopper, allozymes.
Population cytogenetics of Chorthippus vagans. I. Polymorphisms for pericentric inversion and for heterochromatin deletion
Authors: Cabrero Josefa , Camacho Juan Pedro M.
Published: April 2011

Two different polymorphisms have been identified in natural populations of the grasshopper Chorthippus vagans. One of these involved an inversion polymorphism in the M7 chromosome and was present in two populations from Granada. In one of these, from Prados del Pinar, the frequency of this polymorphism was constant over three consecutive generations, and meiotic studies of heterozygous individuals indicated that this inversion had not effect on male fertility. The second polymorphism involved a deletion of the distal C-band of the short arm of the M4 chromosome, which was observed in three different populations. From the observed difference between its frequency in adults and embryos in one of these populations, that of Prados del Pinar, it would appear that this deletion is strongly selected against. Despite this, its frequency was maintained in adult individuals of this population over 2 consecutive years. Complete meiotic drive in favour of the M4–d chromosomes in heterozygous females would explain the maintenance of its frequency despite the fact that it is counterselected.

Key words: Chorthippus, inversion, heterochromatin, polymorphism (chromosome), meiotic drive.
Genetic and cytogenetic analyses of the A genome of Triticum monococcum. IV. Synaptonemal complex formation in autotetraploids
Authors: Gillies C. B. , Kuspira J. , Bhambhani R. N.
Published: April 2011

Electron microscopy of synaptonemal complex spreads from autotetraploid Triticum monococcum (2n = 4x = 28) revealed a minimum mean of 3.59 multivalents per zygotene–pachytene nucleus. The range of values was from 1 to 6 multivalents per nucleus. Most of the multivalents were quadrivalents with single, medially located pairing partner switch points. Lateral element pairing switches, particularly the few multiple switches, were often accompanied by extensive asynapsis around the switch point. The synaptonemal complex multivalent frequency is considerably higher than the metaphase I quadrivalent frequency previously reported for the same material. Calculations of expected pachytene quadrivalent frequency from metaphase I data, using several published theoretical models, gave values that did not agree with the results obtained here. The difference between the multivalent frequencies at pachytene and metaphase I does not appear to be the result of a correction process. Instead, it could be caused by a combination of preferential pairing or crossing-over and the effects of the position of partner switches and asynapsis associated with switches.

Key words: autotetraploid, multivalents, synaptonemal complex, pairing effects.
Genome size variation in North American minnows (Cyprinidae). II. Variation among 20 species
Authors: Gold J. R. , Amemiya C. T.
Published: April 2011

Genome sizes (nuclear DNA contents) from 200 individuals representing 20 species of North American cyprinid fishes (minnows) were examined spectrophotometrically. The distributions of DNA values of individuals within populations of the 20 species were essentially continuous and normal; the distribution of DNA values among species was continuous and overlapping. These observations suggest that changes in DNA quantity in cyprinids are small in amount, involve both gains and losses of DNA, and are cumulative and independent in effect. Significant heterogeneity in mean genome size occurs both between individuals within populations of species and among species. The former averages maximally around 6% of the cyprinid genome and is nearly the same as the amount of DNA theoretically needed for the entire cyprinid structural gene component. The majority of the DNA content variation among the 20 species is distributed above the level of individuals within populations. Comparisons of average genome size difference or distance between individuals drawn from different levels of taxonomic organization indicate that considerably greater divergence in genome size has occurred in the extremely speciose cyprinid genus Notropis as compared with other North American cyprinid genera. This may suggest that genome size change is concentrated in speciation episodes. Finally, no associations were found between interspecific variation in genome size and five life-history characters. This suggests that much of the variation in genome size within and among the 20 species may be phenotypically inconsequential.

Key words: genome size, North American cyprinid fishes, evolution.
Incidence and inheritance of the 1/29 and 14/20 Robertsonian translocations in Canadian beef cattle
Authors: McWhir J. , Church R. B. , Coulter G. H. , Lin C. C.
Published: April 2011

Metaphase chromosomes were prepared from peripheral leukocyte cultures of 253 beef animals representing 21 breeds. A total of 10 Robertsonian translocations were identified. Nine were 1/29 fusions and one was a stable 14/20 fusion identified in several Simmentals. To our knowledge, the only other case of this translocation reported was also in the Simmental breed, suggesting that this fusion may be unique to the breed. A further 54 relatives of known 1/29 and 14/20 carriers were examined, revealing that both fusions were inherited by 50% of offspring of the heterozygous carrier. Heterozygous male 1/29 carriers left fewer calves than karyotypically normal bulls when used in natural service.

Key words: Robertsonian translocation, cattle, chromosomes, fertility.
Pattern of nucleolar organizer region activity during male meiosis in Callicrania seoanei (Orthoptera) as analyzed by silver staining: evidences for a possible reactivation in the period between the two meiotic divisions
Authors: Santos J. , Sentis C. , Fernandez-Piqueras J.
Published: April 2011

Silver staining of spermatocytes and early spermatid nuclei from the neo XY race of the Tettigonioid species Callicrania seoanei reveals an active nucleolar organizer region (NOR) located proximally in a medium-sized bivalent. Ag-positive material was present at the NOR in all stages of male meiosis. However, the results obtained indicate that transcriptional activity of ribosomal cistrons (rDNA) is not maintained throughout spermatogenesis, but that NOR reactivation might occur in the period between the two meiotic divisions in addition to the more general postmeiotical reactivation in the early spermatid nuclei.

Key words: NOR activity, silver staining, male meiosis, Callicrania seoanei (Orthoptera).
Correlations, epistasis, and heterosis of plant height and internode length in barley
Authors: Vazquez J. F. , Sanchez-Monge E.
Published: April 2011

The correlation between total height and its components, and between these and yield components, and the presence of nonallelic interactions and heterosis were studied in barley by means of a 6 × 6 diallel cross. The estimation of interaction and heterosis parameters were made in P1, P2, F1, F2, B1, and B2 generations according to the Jinks and Jones model. Total height had a positive correlation with each internode length. The values of such correlations seemed to indicate that peduncle length could be a good index of total height. The plants with short basal internodes had less total height and longer intermediate internodes. The positive correlation of total height with yield and its components suggests that the selection for short culm and short basal internodes would be to the detriment of yield. The predominant interaction was of the duplicate type, the total height being the character with greater epistasis. In the crosses with heterosis, this was always positive. 'Albacete' × M-168 and A.1.-2 × M-168 were the crosses where the selection for short culm and lodging resistance would be most effective.

Key words: diallel cross, correlations, epistasis, heterosis, barley.
Segmental pycnotic reversion of facultative heterochromatin during the second male meiosis in tettigonioid species (Orthoptera)
Authors: Piqueras J. Fernández , Sentís C.
Published: April 2011

The X chromosome invariably exhibits isopycnosis during the most condensed stages of male meiosis after conventional staining procedures in all studied species of Tettigonioidea (Orthoptera). However, differential negative staining of the X chromosome can be achieved during these stages by a silver impregnation method after extraction of chromosomal proteins with 2 × SSC. This differential response to silver may be indicative of a distinctive chromatin organization in the X chromosome with respect to that of the autosomes. Following 2 × SSC – silver impregnation treatment, pycnotic reversion of part of the X chromosome can be observed from the metaphase II stage on in tettigonioids. Pycnotic reversion is initiated from the telomeric region of the X chromosome in the subfamily Ephyppigerinae, while in the subfamily Pycnogastrinae pycnotic reversion occurs at the centromeric region of this chromosome. These two modes of segmental pycnotic reversion may indicate the onset of a reversion of the facultative heterochromatinized state of the X chromosome (euchromatinization) during male meiosis in tettigonioids. An initiation center may be postulated for this process that is located either at the end distal to or proximal to the centromere of the X chromosome. This hypothesis is supported by the observed pycnotic behaviour of neo-X chromosomes in two different neo-XY systems, one involving centric and the other tandem fusion. Facultative heterochromatinization never involves the autosomally derived segments (XR) of the neo-X chromosomes. Occasional failures in the heterochromatinization process of part of the X chromosome, as well as of the neo-X chromosome, in two species suggests that both facultative heterochromatinization and its reversion are two processes that act segmentally.

Key words: male meiosis, X chromosome, facultative heterochromatin, segmental euchromatinization.
The orientation of multivalents at meiotic metaphase I: a workshop report
Authors: Sybenga J. , Rickards G. K.
Published: April 2011

During a workshop with 13 participants, several aspects of multivalent orientation at meiotic (pro)metaphase were discussed in an attempt to resolve some of the most prominent controversies with respect to terminology, interpretation of observations, and the validity of hypotheses and theories. For several terms and concepts, descriptive definitions were formulated that are recommended for general use. In the analysis of the behaviour of the multivalent in meiosis preprometaphase shape and position as important factors in final orientation were discussed, as well as the first contact between spindle and kinetochores and the role of reorientation. Specific characteristics of different multivalents and expected frequencies of different orientation types were considered. Finally, a few remarks on data collection and analytical procedures were made

Key words: meiosis, multivalents, orientation, workshop.
DNA base composition heterogeneity in the grass genus Briza L.
Authors: King G. J. , Ingrouille M. J.
Published: April 2011

Intragenomic DNA base composition heterogeneity is determined for eight species of Briza L. (Poaceae). High-resolution first-derivative DNA denaturation profiles, recording base composition distribution, provide a "fingerprint" of a species genome. Differences in base composition between species may be explained by chromosome loss or recent sequence amplification events and correlate with relationships established by traditional biosystematic methods. The complex polyphasic profiles can be deconvoluted into a small number of Gaussian curves that accurately represent the complex profile. The physical basis of this representation is demonstrated by affinity chromatography of DNA fragments of at least 600 base pairs, which separates a number of components.

Key words: Briza, DNA base composition, genome heterogeneity, grass systematics, thermal denaturation.
Cytological evidence of terminal deficiencies produced by the r-X1 deletion in maize
Authors: Lin Bor-yaw
Published: April 2011

In addition to monosomes and trisomes, the r-X1 deletion generates chromosome deficiencies of parts of an arm; these deficiencies now have been identified cytologically. Of eight japonica plants produced from the cross of r-X1/R-r as female with the Mangelsdorf's tester, five were complete and three were partial monosomes. The isolated partial monosomes had chromosome breaks in the region between the centromere and the japonica locus. Their breakpoints were at the 0.33, 0.30, and 0.25 positions, respectively, on the long arm of chromosome 8. Additionally, a liguleless plant produced from the same cross carried a partial monosome with a breakpoint at the 0.09 position on the short arm of chromosome 2. Although partial monosomes associated with other chromosome arms have not been investigated, it is evident that the action of the r-X1 deletion is not restricted to the centromeric region of maize chromosomes.

Key words: maize, r-X1 deletion, terminal deficiencies, monosomes.
Synaptic mutants in hexaploid oats (Avena sativa L.)
Authors: Rines H. W. , Johnson S. S.
Published: April 2011

Three meiotic synapsis-deficient mutants of oats (Avena sativa L.) were analyzed to determine their inheritance pattern, detailed chromosomal behavior, and location to chromosome. These highly sterile mutants, one in the cultivar 'Stout' and two in 'Noble', had been recovered from progeny of sodium azide mutagenized populations. Each segregated as a single gene recessive. The only synapsis-deficient variants previously described in hexaploid oats have been nullisomics or ditelosomics. Mutant 'Stout 1212' was classified as asynaptic due to deficiencies in chromosome pairing at all meiotic stages. Mutants 'Noble 1362' and 'Noble 1911' were classified as desynaptic since their homologous chromosomes were paired in early meiosis but they disassociated prematurely in late prophase I. Using a partial monosomic series from the Welsh Plant Breeding Station, mutant 1212 was mapped to monosome XII and is probably a mutation in Syn-5, a gene previously defined only by its nulli effect. Mutants 1362 and 1911 were mapped to monosome IV and are probably mutations in Syn-1, a gene also previously defined only by its nulli effect. Seed set on the synaptic mutant plants in the field was less than 0.2% of that on fertile sibs and likely resulted from pollination by surrounding fertile plants. This seed may serve as a source of unique aneuploid stocks in oats.Key words: meiotic mutants, gene mapping, monosomics, nullisomics, oat cytogenetics.
A genetic analysis of early development in pink (Oncorhynchus gorbuscha) and chum salmon (Oncorhynchus keta) at three different temperatures
Authors: Beacham Terry D.
Published: April 2011

A factorial mating design was employed in which five males were mated to each of five females in each of two stocks for both pink and chum salmon. The resulting embryos and alevins were incubated at constant water temperatures of 4, 8, and 16 °C for pink salmon and 3, 8, and 15 °C for chum salmon. Variation among families in alevin and fry survival rates, hatching, button-up time, length, and weight was the least at 8 °C. Heritability of traits directly correlated with fitness, such as survival rates and button-up time, was low at all temperatures (h2 ≤ 0.25). Maternal effects could account for a substantial portion of the variation in alevin and fry size characters. Nonadditive genetic variance accounted for more of the variation in fry size characters than in those of alevins. Negative genetic correlations were observed between embryo survival and subsequent alevin size and between hatching time and subsequent alevin and fry size. Genotype–temperature interactions could underlie a substantial amount of phenotypic variation in the developmental characters examined for both species.Key words: development, genetic variation, quantitative genetics, salmon.
Correlation of endonuclease activity at meiotic prophase and cofactor-induced genetic recombination in the basidiomycete Coprinus cinereus
Authors: Lu Benjamin C. , Xiu-Yu Li
Published: April 2011

An endonuclease was purified from the basidiocarps of the fungus Coprinus cinereus during late premeiotic S-phase, karyogamy, and pachytene stages of meiosis. This endonuclease causes single-strand nicks on supercoiled PM2 DNA. Its activity is dependent on cofactors such as Mg2+ and Ca2+, and is enhanced by hexaminecobalt chloride and dimethylsulfoxide. Treatments with increasing cofactor concentration elicit increasing enzyme activity in vitro and increasing genetic recombination in vivo. The percent recombination that can be induced by cofactor treatment during late premeiotic S-phase, karyogamy and pachytene is correlated with the amount of endonuclease that can be extracted from the respective stages. These results suggest that Mg2+ and Ca2+ induce genetic recombination by increasing the endonuclease activity that creates nicked and gapped DNA substrates for ensuing recombination events. We believe that the meiotic endonuclease of Coprinus is involved in the early phase of genetic recombination. Cold temperature treatment is known to retard repair activity at pachytene and causes a threefold increase in recombination. Double treatments involving Mg2+ and Ca2+ at karyogamy followed by cold temperature at pachytene result in an additive (more than fourfold) increase in recombination frequency. The peak concentration of the nicking endonuclease is found at late premeiotic S and early karyogamy, whereas the peak activity of the repairing DNA polymerase b is found at late pachytene. The staging of these two enzymes is in good accord with the genetic data.Key words: Coprinus, endonuclease, meiosis, genetic recombination, Z-DNA.
Genetic analysis of mannose-6-phosphate isomerase in soybeans
Authors: Chiang Y. C. , Kiang Y. T.
Published: April 2011

Five mannose-6-phosphate isomerase (EC 5.3.1.8) variants were observed electrophoretically in cultivated soybeans (Glycine max (L.) Merr.) and wild soybeans (G. soja Sieb. &Zucc.). Four of the five variants differed in the mobility of the two mannose-6-phosphate isomerase bands observed, while the fifth showed no enzyme activity. Several crosses involving different variants were made to study inheritance of the observed variants. The inheritance data showed that the five variants were allelic and controlled by a single locus (Mpi). The five alleles were as follows: Mpi-a (Rf 0.61 and 0.66); Mpi-b (Rf 0.66 and 0.7); Mpi-c (Rf 0.71 and 0.75); Mpi-d (Rf 0.76 and 0.80); and mpi. Mpi-a, Mpi-b, Mpi-c, and Mpi-d are codominant, and the null allele mpi is recessive. The Mpi-b allele is most common while the Mpi-d and mpi alleles are rare in both the cultivated and wild soybean germ plasm from various sources examined.Key words: Glycine max, Glycine soja, isozymes, Mpi, gel electrophoresis, allelic frequency.
Mise en évidence de variations saltatoires de l'ADN nucléaire dans et entre les espèces du genre Medicago L.
Authors: Essad S.
Published: April 2011

Forty-two samples representing 20 Medicago L. species were used to determine the nuclear DNA content of each species. Significant intra- and inter-specific variations were evident. The total amplitude of these variations at the 2C level ranged from 1.6 to 9.4 pg, but the maximum significant DNA evolutionary value amounted to 7.2 pg only (Medicago sativa 4x). The occurrence of two nuclear populations from a number of origins was interpreted as corresponding to a fundamental evolutionary value for one of them and to the addition of metabolic DNA for the other. All the values observed were near multiples of a DNA quantum called a "nucleon," which was estimated to be 0.37 pg at the 2C level. This value corresponds to the lower DNA content observed in Angiosperms. Lastly, it appears that the arithmetical distribution of one nucleon among the usual 2n = 16 chromosomes in the genus ascribes a DNA amount of 0.02 pg to each chromatid, the approximate value for a chromosome modulus.Key words: Medicago, DNA content, nucleon, chromosome modules, saltatory genomic evolution.[Journal translation]
Genetic analysis of epicuticular wax production in alfalfa
Authors: Jefferson P. G. , Johnson D. A. , Rumbaugh M. D.
Published: April 2011

Epicuticular wax production increases in drought-stressed plants and has been identified as a potential drought resistance selection criterion. The objective of the present study was to determine the genetic variances and narrow-sense heritability of epicuticular wax production in alfalfa (Medicago sativa L.). These parameters were determined from a 14 parent diallel cross that included all possible progeny combinations. Cross progenies, selfed progenies, and reciprocal crosses were grown in a space-plant nursery at Logan, Utah. Epicuticular wax was determined gravimetrically after washing 100 cm2 of leaves (2.5 g) in carbon tetrachloride. General combining ability was significant (P < 0.05), and estimated heritability was 35% from one harvest in 1985. Specific combining ability and reciprocal effects were not significant. A subset of six parents and their progenies were sampled for two harvests in 1986. The general combining ability by harvest interaction was significant (P < 0.01) for epicuticular wax production, indicating that the true narrow-sense heritability may be lower than 35%. The range in epicuticular wax production among harvests was as great as among progenies. A greater diversity of genetic material would be useful in a selection program for epicuticular wax production in alfalfa.Key words: Medicago sativa, heritability, drought resistance, genetic variability, diallel analysis.
Heterochromatin diversity and chromosome morphology in wheats analyzed by the HKG banding technique
Authors: Shang X. M. , Jackson R. C. , Nguyen H. T.
Published: April 2011

Chromosome banding patterns in diploid, tetraploid, and hexaploid wheats were clearly revealed and compared by the HCl–KOH–Giemsa banding technique. Heterochromatin diversity of chromosomes 4A, 4B, 5B, and satellite chromosomes IB and 6B was shown at the centromeric, pericentric, telomeric, interstitial, and satellite regions. Quantitative comparisons were made of the amount of heterochromatin in chromosomes 4A, 4B, and 5B and among genomes of 'Chinese Spring' (Triticum aestivum). Genome relationships were evaluated in the extant diploid and polyploid wheat taxa. Modifications of the banding technique by hypotonic solution and water treatments and by changing air-drying time of slides influenced centromeric, interstitial, and nucleolar organizer region banding patterns, greatly increased the volume of chromosomes, produced different banding patterns, and significantly changed the nuclear morphologies.Key words: HKG-banding, diversity, chromosomes, genome relationships, Triticum.
Analysis of fidelity mechanisms with eukaryotic DNA replication and repair proteins
Authors: Kunkel Thomas A. , Bebenek Katarzyna , Roberts John D. , Fitzgerald Mary P. , Thomas David C.
Published: April 2011

We are investigating the mechanisms for producing or avoiding errors during DNA synthesis catalyzed by DNA replication and repair proteins purified from eukaryotic sources. Using assays that monitor the fidelity of a single round of DNA synthesis in vitro, we have defined the error frequency and mutational specificity of the four classes of animal cell DNA polymerases (α, β, δ, γ), and the fidelity of an SV40 origin-dependent DNA replication complex in extracts of HeLa cells.Key words: error frequency, repair proteins, polymerases, mutational specificity, fidelity mechanisms.