bluuebunny/crossref_metadata_2025 huggingface dataset:
SO-LAAO, a Novell-Amino Acid Oxidase That EnablesStreptococcus oligofermentansTo OutcompeteStreptococcus mutansby Generating H2O2from Peptone
Authors: Tong Huichun , Chen Wei , Shi Wenyuan , Qi Fengxia , Dong Xiuzhu
Published: May 2008

We previously demonstrated thatStreptococcus oligofermentanssuppressed the growth ofStreptococcus mutans, the primary cariogenic pathogen, by producing hydrogen peroxide (H2O2) through lactate oxidase activity. In this study, we found that theloxmutant ofS. oligofermentansregained the inhibition while growing on peptone-rich plates. Further studies demonstrated that the H2O2produced on peptone byS. oligofermentanswas mainly derived from sevenl-amino acids, i.e.,l-aspartic acid,l-tryptophan,l-lysine,l-isoleucine,l-arginine,l-asparagine, andl-glutamine, indicating the possible existence ofl-amino acid oxidase (LAAO) that can produce H2O2froml-amino acids. Through searching theS. oligofermentansgenome for open reading frames with a conserved flavin adenine dinucleotide binding motif that exists in the known LAAOs, including those of snake venom, fungi, and bacteria, a putative LAAO gene, assigned asaaoSo, was cloned and overexpressed inEscherichia coli. The purified protein, SO-LAAO, showed a molecular mass of 43 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and catalyzed H2O2formation from the sevenl-amino acids determined above, thus confirming its LAAO activity. The SO-LAAO identified inS. oligofermentansdiffered evidently from the known LAAOs in both substrate profile and sequence, suggesting that it could represent a novel LAAO. AnaaoSomutant ofS. oligofermentansdid lose H2O2formation from the sevenl-amino acids, further verifying its function as an LAAO. Furthermore, the inhibition byS. oligofermentansofS. mutansin a peptone-rich mixed-species biofilm was greatly reduced for theaaoSomutant, indicating the gene's importance in interspecies competition.
Release of Small Molecules during Germination of Spores of
Bacillus
Species
Authors: Setlow Barbara , Wahome Paul G. , Setlow Peter
Published: May 2008

Free amino acids, dipicolinic acid, and unidentified small molecules were released early in
Bacillus
spore germination before hydrolysis of the peptidoglycan cortex, but adenine nucleotides and 3-phosphoglycerate were not. These results indicate that early in germination there is a major selective change in the permeability of the spore's inner membrane.
VirB3 to VirB6 and VirB8 to VirB11, but Not VirB7, Are Essential for Mediating Persistence ofBrucellain the Reticuloendothelial System
Authors: den Hartigh Andreas B. , Rolán Hortensia G. , de Jong Maarten F. , Tsolis Renée M.
Published: May 2008

TheBrucella abortus virBlocus contains 12 open reading frames, termedvirB1throughvirB12, which encode a type IV secretion system. Polar mutations in thevirBlocus markedly reduce the ability ofB. abortusto survive in cultured macrophages or to persist in organs of mice. While a nonpolar deletion of thevirB2gene reduces survival in cultured macrophages and in organs of mice, a nonpolar deletion ofvirB1only reduces survival in macrophages, whereasvirB12is dispensable for either virulence trait. Here we investigated the role of the remaining genes in thevirBlocus during survival in macrophages and virulence in mice. Mutants carrying nonpolar deletions of thevirB3,virB4,virB5,virB6,virB7,virB8,virB9,virB10, orvirB11gene were constructed and characterized. All mutations reduced the ability ofB. abortusto survive in J774A.1 mouse macrophage-like cells to a degree similar to that caused by a deletion of the entirevirBlocus. Deletion ofvirB3,virB4,virB5,virB6,virB8,virB9,virB10, orvirB11markedly reduced the ability ofB. abortusto persist in the spleens of mice at 8 weeks after infection. Interestingly, deletion ofvirB7did not reduce the ability ofB. abortusto persist in spleens of mice. We conclude thatvirB2,virB3,virB4,virB5,virB6,virB8,virB9,virB10, andvirB11are essential for virulence ofB. abortusin mice, while functions encoded by thevirB1,virB7, andvirB12genes are not required for persistence in organs with this animal model.
Involvement of a Novel Efflux System in Biofilm-Specific Resistance to Antibiotics
Authors: Zhang Li , Mah Thien-Fah
Published: May 2008

Bacteria growing in biofilms are more resistant to antibiotics than their planktonic counterparts. How this transition occurs is unclear, but it is likely there are multiple mechanisms of resistance that act together in order to provide an increased overall level of resistance to the biofilm. We have identified a novel efflux pump in
Pseudomonas aeruginosa
that is important for biofilm-specific resistance to a subset of antibiotics. Complete deletion of the genes encoding this pump, PA1874 to PA1877 (PA1874-1877) genes, in an
P. aeruginosa
PA14 background results in an increase in sensitivity to tobramycin, gentamicin, and ciprofloxacin, specifically when this mutant strain is growing in a biofilm. This efflux pump is more highly expressed in biofilm cells than in planktonic cells, providing an explanation for why these genes are important for biofilm but not planktonic resistance to antibiotics. Furthermore, expression of these genes in planktonic cells increases their resistance to antibiotics. We have previously shown that
ndvB
is important for biofilm-specific resistance (T. F. Mah, B. Pitts, B. Pellock, G. C. Walker, P. S. Stewart, and G. A. O'Toole, Nature 426:306-310, 2003). Our discovery that combining the
ndvB
mutation with the PA1874-1877 gene deletion results in a mutant strain that is more sensitive to antibiotics than either single mutant strain suggests that
ndvB
and PA1874-1877 contribute to two different mechanisms of biofilm-specific resistance to antibiotics.
Modulation ofcovRExpression inStreptococcus mutansUA159
Authors: Chong Patrick , Drake Laura , Biswas Indranil
Published: May 2008

The biofilm-formingStreptococcus mutansis a gram-positive bacterium that resides in the human oral cavity and is considered to be the primary etiological agent in the formation of dental caries. The global response regulator CovR, which lacks a cognate sensor kinase, is essential for the pathogenesis and biofilm formation of this bacterium, but it is not clear howcovRexpression is regulated inS. mutans. In this communication, we present the results of our studies examining various factors that regulate the expression ofcovRinS. mutansUA159. The results of Southern hybridization and PCR analysis indicated that CovR is an orphan response regulator in various isolates ofS. mutans. The transcriptional start site forcovRwas found to be 221 base pairs upstream of the ATG start codon, and site-directed mutagenesis of the upstream TATAAT box confirmed our findings. The expression ofcovRis growth phase dependent, with maximal expression observed during exponential-growth phase. While changes to the growth temperature did not significantly affect the expression ofcovR, increasing the pH or the concentration of Mg2+in the growth medium leads to an increase incovRexpression. The results of semiquantitative reverse transcriptase PCR analysis and in vivo transcriptional-fusion reporter assays indicated that CovR autoregulates its own expression; this was verified by the results of electrophoretic mobility shift assays and DNase I protection assays, which demonstrated direct binding of CovR to the promoter region. Apparently, regulation by Mg2+and the autoregulation ofcovRare not linked. A detailed analysis of the regulation of CovR may lead to a better understanding of the pathogenesis ofS. mutans, as well as providing further insight into the prevention of dental caries.
FliZ Is a Posttranslational Activator of FlhD
4
C
2
-Dependent Flagellar Gene Expression
Authors: Saini Supreet , Brown Jonathon D. , Aldridge Phillip D. , Rao Christopher V.
Published: May 2008

Flagellar assembly proceeds in a sequential manner, beginning at the base and concluding with the filament. A critical aspect of assembly is that gene expression is coupled to assembly. When cells transition from a nonflagellated to a flagellated state, gene expression is sequential, reflecting the manner in which the flagellum is made. A key mechanism for establishing this temporal hierarchy is the σ
28
-FlgM checkpoint, which couples the expression of late flagellar (P
class3
) genes to the completion of the hook-basal body. In this work, we investigated the role of FliZ in coupling middle flagellar (P
class2
) gene expression to assembly in
Salmonella enterica
serovar Typhimurium. We demonstrate that FliZ is an FlhD
4
C
2
-dependent activator of P
class2
/middle gene expression. Our results suggest that FliZ regulates the concentration of FlhD
4
C
2
posttranslationally. We also demonstrate that FliZ functions independently of the flagellum-specific sigma factor σ
28
and the filament-cap chaperone/FlhD
4
C
2
inhibitor FliT. Furthermore, we show that the previously described ability of σ
28
to activate P
class2
/middle gene expression is, in fact, due to FliZ, as both are expressed from the same overlapping P
class2
and P
class3
promoters at the
fliAZY
locus. We conclude by discussing the role of FliZ regulation with respect to flagellar biosynthesis based on our characterization of gene expression and FliZ's role in swimming and swarming motility.
Repetitive DNA variation and pivotal–differential evolution of wild wheats
Authors: Talbert L. E. , Kimber G. , Magyar G. M. , Buchanan C. B.
Published: May 2008

Several polyploid species in the genus Triticum contain a U genome derived from the diploid T. umbellulatum. In these species, the U genome is considered to be unmodified from the diploid based on chromosome pairing analysis, and it is referred to as pivotal. The additional genome(s) are considered to be modified, and they are thus referred to as differential genomes. The M genome derived from the diploid T. comosum is found in many U genome polyploids. In this study, we cloned three repetitive DNA sequences found primarily in the U genome and two repetitive DNA sequences found primarily in the M genome. We used these to monitor variation for these sequences in a large set of species containing U and M genomes. Investigation of sympatric and allopatric accessions of polyploid species did not show repetitive DNA similarities among sympatric species. This result does not support the idea that the polyploid species are continually exchanging genetic information through introgression. However, it is also possible that repetitive DNA is not a suitable means of addressing the question of introgression. The U genomes of both diploid and polyploid U genome species were similar regarding hybridization patterns observed with U genome probes. Much more variation was found both among diploid T. comosum accessions and polyploids containing M genomes. The observed variation supports the cytogenetic evidence that the M genome is more variable than the U genome. It also raises the possibility that the differential nature of the M genome may be due to variation within the diploid T. comosum, as well as among polyploid M genome species and accessions.Key words: wheat, molecular, evolution, introgression.
Cytogenetics of Elymus magellanicus and its intra- and inter-generic hybrids with Pseudoroegneria spicata, Hordeum violaceum, E. trachycaulus, E. lanceolatus, and E. glaucus (Poaceae: Triticeae)
Authors: Jensen Kevin B.
Published: May 2008

This paper describes the cytogenetics of the South American grass Elymus magellanicus (2n = 4x = 28) and its inter- and intra-generic hybrids with North American Pseudoroegneria spicata (2n = 2x = 14; SS), Iranian Hordeum violaceum (2n = 2x = 14; HH), and North American E. trachycaulus (2n = 4x = 28; SSHH), E. lanceolatus (2n = 4x = 28; SSHH), and E. glaucus (2n = 4x = 28; SSHH). Chromosome pairing in the F1 hybrid of E. magellanicus × P. spicata (2n = 3x = 21) averaged 4.09 bivalents per cell. Bivalent frequencies in the E. magellanicus × H. violaceum (2n = 3x = 21) averaged 4.86 bivalents per cell. Bivalent formation (frequencies) in hybrids between North and South American tetraploids averaged 11.42 in E. magellanicus × E. trachycaulus, 13.02 in E. magellanicus × E. lanceolatus, and 10.91 in E. magellanicus × E. glaucus. Meiotic data demonstrated that E. magellanicus is an allotetraploid having the same basic genomes (SSHH) as North American E. trachycaulus, E. lanceolatus, and E. glaucus.Key words: chromosome pairing, meiosis.
Genome constitution of the Australian hexaploid grass Elymus scabrus (Poaceae: Triticeae)
Authors: Torabinejad J. , Mueller R. J.
Published: May 2008

Eight intergeneric hybrid plants were obtained between Elymus scabrus (2n = 6x = 42, SSYY??) and Australopyrum pectinatum ssp. retrofractum (2n = 2x = 14, WW). The hybrids were vegetatively vigorous but reproductively sterile. Examination of pollen mother cells at metaphase I revealed an average of 16.63 I, 5.29 II, 0.19 III, and 0.05 IV per cell for the eight hybrids. The average chiasma frequency of 6.77 per cell in the above hybrids strongly supports the presence of a W genome from A. pectinatum ssp. retrofractum in E. scabrus. Meiotic pairing data of some other interspecific hybrids suggest the existence of the SY genomes in E. scabrus. Therefore, the genome constitution of E. scabrus should be written as SSYYWW. Two other hybrid plants resulted from Elymus yezoensis (2n = 4x = 28, SSYY) crosses with A. pectinatum ssp. pectinatum (2n = 2x = 14, WW). Both were weak and sterile. An average of 0.45 bivalents per cell were observed at metaphase I. This clearly indicates a lack of pairing between W genome of Australopyrum and S or Y genomes of E. yezoensis. In addition, six hybrid plants of E. scabrus with Psathyrostachys juncea (2n = 2x = 14, NN) and one with Thinopyrum bessarabicum (2n = 2x = 14, JJ) were also obtained. The average bivalents per cell formed in both combinations were 2.84 and 0.70, respectively. The results of the latter two combinations showed that there is no N or J genome in E. scabrus.Key words: wide hybridization, chromosome pairing, genome analysis, Australopyrum, Elymus.
Primers that amplify inserts in a multicloning site also hybridize to Sorghum bicolor DNA
Authors: Xu G.-W. , Magill C. W. , Hart G. E.
Published: May 2008

One or both members of a pair of primers developed to permit polymerase chain reaction amplification of sorghum DNA fragments cloned into the PstI site of pUC18 were shown to hybridize to sorghum DNA. The presence of the same primer sequences on the ends of amplified inserts posed a problem in using the amplified inserts as hybridization probes because the high signal level of the primer-detected DNA fragments often obscured the segregation patterns of the restriction fragments detected by the insert DNA. Conditions that favor annealing of the insert rather than the primers were experimentally defined, however, so that directly amplified DNA sequences could be used as RFLP probes. Cosegregation analysis of 51 F2 individuals from a cross between BTx 623 and IS 3620C established a linkage group containing the Pd1 locus. Alleles at the locus are revealed as codominant bands on Southern blots of heterozygotes, but the segregation ratio among the F2 progeny deviated significantly from the expected 1:2:1. The distortion favored the allele from parent BTx 623.Key words: polymerase chain reaction, restriction fragment length polymorphism, Sorghum bicolor, linkage mapping.
Direct end labelling of telomeres
Authors: Kolchinsky Alexander , Gresshoff Peter M.
Published: May 2008

A novel approach of direct end labelling of telomeres is presented. Chromosome-sized, agarose-embedded DNA was treated with T4 DNA polymerase to remove protruding 3′ end of telomeres and to generate single-stranded 5′ ends. The DNA was then labelled by the same enzyme in the presence of [α-32P|dGTP and cold dATP and dTTP. Labelled yeast chromosomes separated by pulsed field gel electrophoresis maintained their integrity. Digestion of yeast chromosomes separated in pulsed field gels with a restriction nuclease (HinfI), followed by conventional electrophoresis in the second dimension, resulted in a fingerprint-like pattern of labelled telomeres. This was very similar to the hybridization pattern of a similar two-dimensional gel probed with cloned yeast telomeric sequence. The same approach enabled us to label telomeres in soybean, determine their size, and to reveal polymorphisms in the length of telomeres between the closely related subspecies Glycine max (soybean) and Glycine soja.Key words: telomeres, Saccharomyces cerevisiae, Glycine max, two-dimensional electrophoresis, DNA polymorphism.
Identification of short tandemly repeated sequences in extrachromosomal circular DNAs from Drosophila melanogaster embryos
Authors: Renault S. , Degroote F. , Picard G.
Published: May 2008

A sequence (scl) belonging to the recently identified dodeca satellite family was found to be a major family of extrachromosomal circular DNA molecules from Drosophila melanogaster embryos. The basic unit consists of the 11-bp repeat 5′ ACTGGTCCCGT 3′, is 63% G + C rich, and shares some similarity with the Escherichia coli chi sequence. This family accounts for only about 0.06% of the genome but very likely for a higher proportion of the circular DNA molecules. It is organized in the genome into at least five main clusters contained in DNA fragments larger than 20 kb and several minor clusters. These clusters are located in the heterochromatic pericentromeric regions. Two other families of simple repeated sequences, the 1.686 g/cm3 (5′ AATAACATAG 3′) and the 1.705 g/cm3 (5′ AAGAG 3′) satellite DNAs, were also found in circular DNAs, while another family, the 1.672 g/cm3 (5′ AATAT 3′), was not detected. The representation of the simple repeated sequences in circular molecules is not correlated to their genomic representation. Among the seven families of sequences identified to date in extrachromosomal circular DNAs from embryos, the dodeca satellite, the 240-bp repeat of the rDNA intergenic spacer, and the 1.688 and 1.705 g/cm3 satellite DNAs are the most represented families, while the 5S genes, the histone genes, and the 1.686 g/cm3 satellite DNA are present in a lower amount.Key words: D. melanogaster, extrachromosomal circular DNAs, repeated sequences, satellite DNA.
Field performance and heavy metal concentrations of transgenic flue-cured tobacco expressing a mammalian metallothionein-β-glucuronidase gene fusion
Authors: Brandle J. E. , Labbe H. , Hattori J. , Miki B. L.
Published: May 2008

Cadmium (Cd) is a nonessential heavy metal that can cause acute and chronic illness in humans. Some plant species such as tobacco (Nicotiana tabacum L.) tend to accumulate high levels of Cd in leaf tissue, the consumed portion of the plant. Tissue-specific expression of mammalian metallothionein has been suggested as a means of partitioning Cd in nonconsumed portions of transgenic plants. The purpose of the experiment reported here was to evaluate Cd concentration and agronomic performance of four field-grown transgenic tobacco lines harbouring a metallothionein-β-glucuronidase (MG) gene fusion driven by the constitutive 35S promoter of cauliflower mosaic virus. The trial was grown in a region of Canada known to have high background levels of Cd. The agronomic evaluation showed that some of the transgenic lines were equal to, while others performed more poorly than, the untransformed control for yield, days to flower, and leaf number. Gene expression measured by β-glucuronidase activity showed that all of the transgenic lines expressed the MG gene in the upper portion of the plant. One line did not express the MG gene in the roots. Cd levels in the leaf tissue of transformed lines were not significantly different from the untransformed control.Key words: cadmium, β-glucuronidase, transformation, heavy metal tolerance.
In situ nick translation of meiotic chromosomes to demonstrate homologous heterochromatin heterogeneity
Authors: Torre J. de la , López-Fernández C. , Herrero P. , Gosálvez J.
Published: May 2008

The in situ nick translation procedure performed on fixed meiotic chromosomes partially cleaved with restriction endonucleases shows a different staining of homologous heterochromatic regions, which could be explained through a differential restriction endonuclease cleavage. Mutations occurring before massive tandem duplication and involving those DNA motifs that produce these heterochromatic blocks, together with the absence of DNA recombination that characterizes these particular regions, could explain the observed results. This method for chromosome labelling is most useful to demonstrate a certain level of heterochromatin heterogeneity that is present in the genome of living species but remained cryptic to other techniques that are also able to induce longitudinal differentiation of the chromosomes.Key words: cytogenetics, nick translation, meiosis, heterochromatin.
Combining mutations for the two homoeologous pairing suppressor genes Ph1 and Ph2 in common wheat and in hybrids with alien Triticeae
Authors: Ceoloni Carla , Donini Paolo
Published: May 2008

Two lines of common wheat cv. Chinese Spring, carrying simultaneous mutations for the two major homoeologous pairing wheat suppressor genes Ph1 and Ph2 have been developed and their pairing behaviour compared with that of the ph1b mutant of the same cultivar. Besides carrying the ph1b mutation, the first double mutant line lacked the chromosome arm pair 3DS, containing Ph2, whereas the second had a euploid constitution and carried the ph1b allele on 3DS. Hybrids of Aegilops variabilis and Secale cereale with mono-5B (ph1b) and 3D/3DL plants have also been obtained, where the 3D versus 3DL presence marked the two pairing alternatives (ph1b only and ph1b + Ph2−, respectively). In the wheat × Ae. variabilis hybrids, an 8% increase in total chromosome pairing, almost entirely ascribable to an increment of multivalent associations, was observed in the 2n = 34 + t plants with respect to their 2n = 35 sibs. The number of bivalents showed no significant difference, but a tendency towards a decrease, which was significant for the rod types, was exhibited by the Ph2− plants. A weaker but similar effect was observed in wheat itself. The different mutants, in fact, showed a similar percentage of paired chromosomes but varied in their pairing pattern. A significant reduction in the number of bivalents, owing to a decrease of the rings, only partly compensated for by an increase of the rods, was observed in the double mutants. They also exhibited an increase in the multivalent fraction, which was significant for the most complex associations. In both common wheat and its hybrids with Ae. variabilis the addition of a ph2 mutation thus seems to reinforce the ph1b effect in promoting homoeologous pairing. On the other hand, such an effect was not noticed in the wheat × S. cereale hybrids. However, possible quantitative differences could have been masked by the considerable plant-to-plant variation and potential differences in relative incidence of wheat–wheat versus wheat–rye associations were undetectable in the Feulgen-stained materials analyzed.Key words: common wheat, interspecific hybrids, homoeologous pairing, Ph mutations.
Highly effective cell synchronization in plant roots by hydroxyurea and amiprophos-methyl or colchicine
Authors: Pan W. H. , Houben A. , Schlegel R.
Published: May 2008

Effective somatic cell synchronization in root-tip meristems and improved chromosome spreading were achieved in white campion, wheat, rye, and barley by application of hydroxyurea and amiprophos-methyl or colchicine, combined with a pretreatment of ice water and modified fixative, as well as enzymatic digestion of the meristems. The protocol provides metaphase indices of approximately 50%. The chromosomes and chromosomal DNA were with minimum distortion, providing useful material for chromosome banding studies, in situ DNA–DNA hybridization, microdissection, and microcloning.Key words: Melandrium album, rye, wheat, barley, cell cycle, root meristem, synchronization, metaphase index, chromosome preparation.
Genomic diversity in aneudiploid (2n = 38) and diploid (2n = 40) Glycine tomentella revealed by cytogenetic and biochemical methods
Authors: Kollipara K. P. , Singh R. J. , Hymowitz T.
Published: May 2008

Of the 15 perennial species of the subgenus Glycine Willd., G. tomentella Hayata is unique in that it has four cytotypes (2n = 38, 40, 78, and 80) and a wide range of geographical distributions. The objective of this study was to uncover the genomic diversity among accessions of aneudiploid (2n = 38) and diploid (2n = 40) G. tomentella based on crossability rate, hybrid seed and seedling viability, meiotic chromosome pairing of F1 hybrids, and seed protein and protease inhibitor profiles. Aneudiploid and diploid G. tomentella accessions were divided into two (D1 and D2) and three [D3(A,B,C), D4, and D5] groups, respectively, based on previous isozyme studies. Crossability rate, intergenomic hybrid viability, degree of chromosome pairing, total seed protein profiles, and trypsin and chymotrypsin inhibitor banding patterns confirmed the isozyme grouping with minor disagreements. A consistent variation was not observed among the aneudiploid accessions in any method of analysis used in this study. Similarly, cytogenetic analysis and the total seed protein profiles did not show dissimilarity among the accessions from Papua New Guinea (PNG; the D3 group) and north of Mitchell River in Northern Queensland [N.Qld(n)]. However, trypsin and chymotrypsin inhibitor analysis revealed that the PNG accessions were distinctly different from N.Qld(n) accessions. The D4 and D5 group accessions were clearly distinguishable by both cytogenetic and biochemical methods. Thus, this study indicates the presence of four genomic groups among G. tomentella (2n = 38, 40) accessions, including the aneudiploids D1 and D2 in one group and diploids in three groups (D3, D4, and D5). These findings will be useful in further genome analysis and add to our present understanding of the biosystematics of the genus Glycine.Key words: Glycine tomentella, genome, cytogenetics, seed proteins profiles, protease inhibitors.
Construction of a molecular linkage map of pepper and a comparison of synteny with tomato
Authors: Prince James P. , Pochard Edmond , Tanksley Steven D.
Published: May 2008

A molecular map of pepper (Capsicum sp.) totalling 720 cM has been constructed in an interspecific F2 cross with restriction fragment length polymorphisms and isozymes. Nineteen linkage groups were formed from 192 molecular markers. Twenty-six markers showed no linkage to any others. Twenty-eight markers showed significant deviation from expected Mendelian ratios and clustered in the genome. Two quantitative trait loci controlling the number of flowers per node were mapped to linkage group 10. The order of markers in at least 228 cM (31.7%) of the pepper genome is conserved with respect to the tomato genome, with a minimum of 15 chromosome breakage events postulated to have occurred since their divergence from a common ancestor. Comparisons of meiotic recombination in 14 conserved intervals indicates that tomato has a higher rate of recombination than does pepper in the crosses studied. Evidence suggests that centric fusions and resulting chromosome breakage events are mechanisms for genome evolution in the Solanaceae.Key words: restriction fragment length polymorphism, genome evolution, quantitative trait loci, multiple flowers, Capsicum, Lycopersicon esculentum.
Cytogenetic studies in wheat. XV. Location of rust resistance genes in VPM1 and their genetic linkage with other disease resistance genes in chromosome 2A
Authors: Bariana H. S. , McIntosh R. A.
Published: May 2008

Inheritance studies showed that the VPM1-derived seedling resistances to stem rust, stripe rust, leaf rust, and powdery mildew were controlled by single genes; the genes for rust resistance were designated Sr38, Yr17, and Lr37, respectively, whereas the gene for resistance to powdery mildew was postulated to be Pm4b. Sr38, Yr17, and Lr37 were shown to be closely linked and distally located in the short arm of chromosome 2A. They showed very close repulsion linkage with Lr17 and were genetically independent of other genes known to be located in chromosome 2A. Previously unmapped, Yr1 appeared to be distally located in the long arm of chromosome 2A.Key words: stem rust, stripe rust, leaf rust, powdery mildew, monosomic analysis, telocentric mapping, genetic linkage.
Simultaneous discrimination of the three genomes in hexaploid wheat by multicolor fluorescence in situ hybridization using total genomic and highly repeated DNA probes
Authors: Mukai Yasuhiko , Nakahara Yumiko , Yamamoto Maki
Published: May 2008

Common wheat, Triticum aestivum, is an allohexaploid species consisting of three different genomes (A, B, and D). The three genomes were simultaneously discriminated with different colors. Biotinylated total genomic DNA of the diploid A genome progenitor Triticum urartu, digoxigenin-labeled total genomic DNA of the diploid D genome progenitor Aegilops squarrosa, and nonlabeled total genomic DNA of one of the possible B genome progenitors Ae. speltoides were hybridized in situ to metaphase chromosome spreads of Triticum aestivum cv. Chinese Spring. For detection, only two fluorochromes, fluorescein and rhodamine, were used. The A, B, and D genomes were simultaneously detected by their yellow, brown, and orange fluorescence, respectively. The genomic fluorescence in situ hybridization pattern of chromosome 4A of cv. Chinese Spring wheat showed that the distal 32% of the long arm was derived from a B genome chromosome. Furthermore, by using two highly repeated sequence probes, pSc 119.2 and pAsl, and two fluorochromes simultaneously, we were able to identify all B and D genome chromosomes and chromosomes 1A, 4A, and 5A of wheat.Key words: common wheat, in situ hybridization, multicolor fluorescence.
Pycnotic cycle of the sex chromosome of Pyrgomorpha conica (Orthoptera) and development of spermiogenesis
Authors: Antonio Carmen , Gonzalez-Garcia Jose M. , Suja Jose A.
Published: May 2008

We have analyzed the anomalous pycnotic cycle of the X sex chromosome of the grasshopper Pyrgomorpha conica throughout both meiotic divisions and its possible influence on spermiogenesis. During diplotene the sex chromosome shows two differentiated pycnotic regions: (i) the centromeric region, which is negatively heteropycnotic, and (ii) the noncentromeric region, which shows alternating negatively and positively heteropycnotic zones in all standard individuals. The variation in size and location of the negative heteropycnotic zones, their smooth appearance, and their lack of effect on spermiogenesis lead us to suggest that condensation differences and not euchromatinization are responsible for their presence. In two individuals the sex chromosome appeared partially isopycnotic at metaphase I, and high levels of abnormal spermatids (macrospermatids and microspermatids) were found. We suggest that the possible activity of this chromosome during the second meiotic division may promote the disruption of spermiogenesis by affecting the mechanism that maintains intercellular bridges between normal spermatids.Key words: sex chromosome, heterochromatin, heteropycnosis, meiosis, spermiogenesis.
Genome constitutions of Thinopyrum curvifolium, T. scirpeum, T. distichum, and T. junceum (Triticeae: Gramineae)
Authors: Liu Zhi-Wu , Wang Richard R.-C.
Published: May 2008

The objective of this study is to elucidate genome constitutions of Thinopyrum curvifolium (Lange) D.R. Dewey, T. scirpeum (K. Presl) D.R. Dewey, T. distichum (Thunb.) A. Löve, and T. junceum (L.) A. Löve. Hybrids of T. sartorii (Boiss. &Heidr.) A. Löve with T. scirpeum and T. junceum, as well as the hybrid between T. curvifolium and Pseudoroegneria geniculata ssp. scythica (Nevski) A. Löve, were made and chromosome pairing at metaphase I was studied. The karyotype analyses of mitotic cells stained by aceto-orcein were conducted for both hybrids and the four target species. The Giemsa C-banding following acetocarmine staining was carried out for the above species and the triploid hybrid T. curvifolium × T. bessarabicum (Savul &Rayss) A. Löve. Meiotic data indicate that all target species have two sets of the basic genome J, but they behave like true allopolyploids because of bivalentization. Karyotypes of T. curvifolium and its triploid hybrid with T. bessarabicum indicate that T. curvifolium contains two different versions of the Jb genome, designated as Jb3 and Jb4, rather than two Je genomes as previously believed. Thinopyrum scirpeum and T. elongatum (4x) have similar karyotypes. Both are segmental allotetraploids carrying two forms of the Je genome. Their genome formulae are Je2 Je3 and Je1 Je3, respectively. Thinopyrum distichum has a karyotype similar to T. junceiforme, which has the Jb2 Je2 genome formula. However, the two species differ in C-banding patterns, reflecting their geographical separation. Thinopyrum junceum is a hexaploid with two pairs of Jb2 genomes and one pair of the Je2 genome, and it has a C-banding pattern similar to that of T. junceiforme, which has one pair each of the Jb2 and Je2 genomes.Key words: genome, meiosis, karyotype, C-banding, Triticeae, Thinopyrum.
Karyotype, C-banding, and Ag-NOR analysis in Diplodus bellottii (Sparidae, Perciforms). Intra-individual polymorphism involving heterochromatic regions
Authors: Amores A. , Martinez G. , Reina J. , Alvarez M. C.
Published: May 2008

A karyotype analysis was carried out in nine specimens of the Sparid species Diplodus bellottii using conventional staining, as well as C-banding and Ag-NOR banding techniques, showing, respectively, 2n = 46 and fundamental number (FN) = 54, and scarce heterochromatic areas irregularly distributed and up to four NOR active regions that were C positive. When compared with the karyotypes of other related species, one centric fusion giving rise to a large metacentric pair and several pericentric inversions seem to have been involved in the karyotype evolution. An intra-individual polymorphism was detected in one specimen, resulting in two karyotypic forms in roughly identical proportion, owing to a larger C-band by the NOR regions, appearing either in a terminal position of the short arms of pair 2 or in telomeric position of pair 3. These findings suggest that the extra heterochromatic segment responsible for the heteromorphism apparently only involves associated heterochromatin and not the NORs themselves. This C-positive block seems to have eventually been transferred between heterologous NOR chromosomes by a somatic event, facilitated by the physical proximity of NOR pairs in the nucleolus.Key words: Sparidae, karyotype, heterochromatin, nucleolus organizers, chromosome polymorphism.
Gliadin alleles in Canadian western red spring wheat cultivars: use of two different procedures of acid polyacrylamide gel electrophoresis for gliadin separation
Authors: Metakovsky E. V. , Ng P. K. W. , Chernakov V. M. , Pogna N. E. , Bushuk W.
Published: May 2008

Gliadin allele compositions of 21 Canadian spring common wheat cultivars, most of which belong to the Canada western red spring (CWRS) class, were studied and great similarity in their genotypes was confirmed. It was found that alleles frequent in the set of Canadian wheats (such as Gli-B1d, Gli-D1j, Gli-A2m, and Gli-D2h) are very rare or absent in common wheat cultivars from other regions and countries studied earlier, indicating that germplasm of CWRS cultivars is rather unique. It may be suggested that alleles frequent in Canadian cultivars relate to important technological characteristics of these wheats and may possibly serve as marker genes during selection for quality traits. Similarity of gliadin electrophoregrams obtained by two different acid polyacryl-amide gel electrophoretic procedures for the same genotype was established, and the component composition of allelic variants of blocks of gliadin components found in the set of Canadian cultivars and in standard cultivars Chinese Spring and Bezostaya 1 are described.Key words: gliadin alleles, acid polyacrylamide gel electrophoresis, Canadian bread wheats.
Molecular cytogenetics of the ribosomal (18S + 28S and 5S) DNA loci in primitive and advanced urodele amphibians
Authors: Lucchini Stefania De , Nardi Irma , Barsacchi Giuseppina , Batistoni Renata , Andronico Francesca
Published: May 2008

In the present work we performed a cytogenetic analysis of the ribosomal (18S + 28S and 5S) loci in amphibian species belonging to the advanced family Salamandridae (genera Triturus, Salamandra, and Salamandrina) and in the primitive hynobiid Salamandrella keyserlingii (family Hynobiidae). In each analyzed karyotype the 5S rDNA sites appear to be stable, and definite in number, while an intraspecific variability both in number and chromosomal location of the 18S + 28S rDNA loci has been found in some Triturus species. In particular, an evolutionary trend toward a large intraspecific variability of the 18S + 28S rDNA loci has been found in the T. vulgaris species group. A structural analysis of the ribosomal repetition units demonstrates the occurrence of a length polymorphism within the 18S + 28S rDNA repeats in the examined species of the family Salamandridae; however, this polymorphism is rather limited, even in those Triturus species characterized by high intragenomic variability of the ribosomal sites. We show that in T. vulgaris meridionalis the variant repetition units actually segregate with individual chromosomes. This implies that they are not intermingled in the ribosomal clusters.Key words: molecular cytogenetics, ribosomal genes, Salamandridae, Hynobiidae.
Physical mapping of rDNA loci in Brassica species
Authors: Maluszynska J. , Heslop-Harrison J. S.
Published: May 2008

The number of major rDNA loci (the genes coding for 18S–5.8S–26S rRNA) was investigated in the economically important Brassica species and their wild relatives by in situ hybridization of an rDNA probe to metaphase chromosomes and interphase nuclei. The diploid species B. nigra (B genome) has two major pairs of rDNA loci, B. oleracea (C genome) has two major pairs and one minor pair of loci, while B. campestris (A genome) has five pairs of loci. Among the three tetraploid species arising from these three diploid ancestors, B. carinata (BBCC genomes) has four loci, B. juncea (AABB genomes) has five major pairs and one minor pair of loci, and B. napus (AACC genomes) has six pairs of loci, indicating that the number of loci has been reduced during evolution. The complexity of the known rDNA restriction fragment length polymorphism patterns gave little indication of number of rDNA loci. It is probable that chromosome rearrangements have occurred during evolution of the amphidiploid species. The data will be useful for physical mapping of genes relative to rDNA loci, micro- and macro-evolutionary studies and analysis of aneuploids including addition and substitution lines used in Brassica breeding programs.Key words: Brassica, centromeric DNA, genetic maps, nuclear architecture, ribosomal DNA, evolution, Brassicaceae, Cruciferae, gene mapping.
Sequential chromosome banding and in situ hybridization analysis
Authors: Jiang Jiming , Gill Bikram S.
Published: May 2008

Different combinations of chromosome N- or C-banding with in situ hybridization (ISH) or genomic in situ hybridization (GISH) were sequentially performed on metaphase chromosomes of wheat. A modified N-banding–ISH/GISH sequential procedure gave best results. Similarly, a modified C-banding – ISH/GISH procedure also gave satisfactory results. The variation of the hot acid treatment in the standard chromosome N- or C-banding procedures was the major factor affecting the resolution of the subsequent ISH and GISH. By the sequential chromosome banding – ISH/GISH analysis, multicopy DNA sequences and the breakpoints of wheat–alien translocations were directly allocated to specific chromosomes of wheat. The sequential chromosome banding– ISH/GISH technique should be widely applicable in genome mapping, especially in cytogenetic and molecular mapping of heterochromatic and euchromatic regions of plant and animal chromosomes.Key words: N-banding, C-banding, in situ hybridization, genomic in situ hybridization.
Evidence from a maize desynaptic mutant points to a probable role of synaptonemal complex central region components in provision for subsequent chiasma maintenance
Authors: Maguire M. P. , Riess R. W. , Paredes A. M.
Published: May 2008

Homozygotes for the dsy1 desynaptic mutant of maize show massive failure of chiasma maintenance during diplotene and diakinesis. Although some chiasmata persist until anaphase I in most microsporocytes expressing this mutant, homozygotes are completely or nearly completely sterile, owing apparently to disjunctive irregularities. Pachytene synaptic errors and some synaptic failure also are found, but recombination nodules are common in homologously synapsed regions, and equational separation of a heterozygous knob into univalents or open arms at diakinesis clearly demonstrates that chiasma failure occurs following crossing-over. A wider than normal synaptonemal complex central region and uniform apparent weakness of central region cross connections to spreading procedures strongly suggest the presence of a genetic lesion in a synaptonemal complex central region component. The dsy1 mutant may provide an especially important source of material for molecular studies on the nature of chiasma maintenance mechanism.Key words: chiasma maintenance, synaptonemal complex, meiotic mutant.
Primer-induced in situ hybridization to plant chromosomes
Authors: Abbo S. , Miller T. E. , King I. P.
Published: May 2008

Primer-induced in situ hybridization of high copy sequences was used successfully on rye mitotic chromosome spreads. Nucleolus organizer sequences were detected in rye, and the pattern obtained was in full agreement with previously reported results by conventional in situ hybridization. The future potential of the primer-induced in situ hybridization technique is briefly discussed.Key words: primer-induced in situ hybridization, rye (Secale cereale L.), nucleolus organizer region.
Segregation of random amplified polymorphic DNA markers and strategies for molecular mapping in tetraploid alfalfa
Authors: Yu K. F. , Pauls K. P.
Published: May 2008

An F1 population was used to analyze the inheritance of random amplified polymorphic DNA (RAPD) markers in tetraploid alfalfa. Of the 32 RAPD markers that were used for a segregation analysis in this study, 27 gave ratios that are consistent with random chromosome and random chromatid segregation at meiosis. However, among all of the RAPD markers (121) that were screened in this study, only one example of a double reduction, that is typical of chromatid segregation, was observed. These results indicate that random chromosome segregation is likely the predominant but not the exclusive mode of inheritance for tetraploid alfalfa. χ2 analyses of cosegregation for RAPD marker pairs derived from the female parent revealed nine linkages that fell into four linkage groups. The recombination fractions among linked marker pairs ranged from 1 to 37%. These are the first molecular linkage groups reported in tetraploid alfalfa. In addition, various strategies for molecular mapping in the tetraploid alfalfa genome are proposed that should be of interest to plant breeders who are planning to use molecular markers for alfalfa or other tetraploid species.Key words: RAPD markers, tetraploid alfalfa, segregation, linkage groups.
Genetic variation in paw preference (handedness) in the mouse
Authors: Biddle Fred G. , Coffaro Cristina M. , Ziehr Jeanette E. , Eales Brenda A.
Published: May 2008

Lateralization of paw preference in laboratory mice in a single-paw reaching task has been used as a model system for left- and right-hand usage. Given a set number of paw reaches for food from a centrally placed food tube, an individual mouse will exhibit a reliable number of left and right paw reaches. Within any single inbred strain, there are approximately equal numbers of left-pawed and right-pawed mice. Nevertheless, significant strain differences have been reported for the degree of lateralization of paw preference. We report here a systematic survey of paw preference in 12 inbred strains of the mouse in which the degree of lateralization falls into two groups of weakly lateralized and highly lateralized paw preference. The genetic inference is that a single major gene may control some function, and alternate alleles at this locus are expressed as weakly and highly lateralized paw preference. Reciprocal crosses indicate the trait is additive with no maternal or X-linked effects. The direction of paw preference has previously appeared to be genetically neutral, but in some strains there is evidence of significant deviation of the numbers of mice to the left and right of equal paw usage, independent of degree of lateralization, and this suggests that direction of left–right paw usage may be a separate genetic trait in the mouse model.Key words: behavioural genetics, paw preference, handedness, mouse.
Clusters of interspersed repeated DNA sequences in the rice genome (Oryza)
Authors: Zhao Xinping , Kochert Gary
Published: May 2008

We have characterized a repeated DNA sequence (RTL 122) from rice (Oryza sauva L.) with respect to its organization in the rice genome and its distribution among rice and other plants. The results indicate that the RTL 122 sequence is interspersed in the rice genome and limited to the genus Oryza. It is highly polymorphic and can be used to fingerprint rice varieties. A structure was observed in which several repeated sequences were clustered in DNA regions of 15–20 kb. We characterized three bacteriophage lambda clones that contained the RTL 122 sequence. Southern analysis using probes derived from restriction fragments of the three lambda clones indicated that all fragments except one are interspersed repeated sequences and belong to different repeated sequence families. Subsequent slot blot hybridization showed that most of them are only present within the genus Oryza. Some of the Oryza-specific, physically linked sequences show the same phylogenetic distribution, which suggests that these sequences might have evolved in a coordinate fashion. On the other hand, some of the repeated sequences have a different distribution even though they are physically adjacent in the genome. We speculate that such blocks of interspersed repeated sequences may serve as hotspots for rapid changes in the rice genome.Key words: rice, Oryza, repeated sequences, DNA fingerprinting, coordinated evolution.
A study of homologous chromosomes using a morphometric approach
Authors: Mark Hon Fong L. , Wyandt Herman E. , Pan Teddy , Mark Jr. Roger , Parmenter Marjorie , Campbell William , Mark Yvonne
Published: May 2008

A previous study of 100 karyotyped metaphase cells has demonstrated the utility of a graphic arts tool in deriving chromosome measurements for relative length determination. In the present study we utilize this same approach to address the question: "What are the average differences in relative lengths between apparently normal homologous chromosomes?" Normal standards derived from this study will be useful for testing specific hypotheses involving heteromorphic differences between homologs. No such data on normal controls could readily be found in either An International System for Human Cytogenetic Nomenclature (1985) or elsewhere.Key words: chromosome relative length, chromosome morphometry, homologous chromosomes.