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1.
Benjamin C KirkupJr LeeAnn Chang Sarah Chang Dirk Gevers Martin F Polz 《BMC microbiology》2010,10(1):137
Background
While most gamma proteobacteria have a single circular chromosome, Vibrionales have two circular chromosomes. Horizontal gene transfer is common among Vibrios, and in light of this genetic mobility, it is an open question to what extent the two chromosomes themselves share a common history since their formation. 相似文献2.
Sugawara H Iwabata K Koshiyama A Yanai T Daikuhara Y Namekawa SH Hamada FN Sakaguchi K 《Chromosoma》2009,118(1):127-139
Mer3 is an evolutionarily conserved DNA helicase that has crucial roles in meiotic recombination and crossover formation.
We have identified the MER3 homolog in Coprinus cinereus (Ccmer3) and show that it is expressed in zygotene and pachytene meiocytes. Immunostaining analysis indicated that CcMer3 was localized
on chromosomes at zygotene and pachytene and CcMer3 foci were more frequent on paired than unpaired chromosomes. We generated
a C. cinereus mer3 mutant (#1) and found that it showed abnormal meiosis progression and underwent apoptosis after prophase I. Basidiospore
production in #1 was reduced to 0.8% of the wild-type level; the spores showed slower germination at 25°C but were similar
to the wild type at 37°C. Electron microscopic analysis of chromosome spreads revealed that axial elements were formed in
the mutant but that synapsis was defective, resulting in a reduction in spore production. Our results demonstrate that CcMer3
is required for synaptonemal complex formation after axial elements align and is thus essential for homologous synapsis. 相似文献
3.
Radim Cegan Gabriel AB Marais Hana Kubekova Nicolas Blavet Alex Widmer Boris Vyskot Jaroslav Doležel Jan Šafář Roman Hobza 《BMC plant biology》2010,10(1):180
Background
The evolution of sex chromosomes is often accompanied by gene or chromosome rearrangements. Recently, the gene AP3 was characterized in the dioecious plant species Silene latifolia. It was suggested that this gene had been transferred from an autosome to the Y chromosome. 相似文献4.
Yueh-Hsiang Yu Yi-Wen Lin Jane-Fang Yu Werner Schempp Pauline H Yen 《BMC evolutionary biology》2008,8(1):96
Background
The Azoospermia Factor c (AZFc) region of the human Y chromosome is a unique product of segmental duplication. It consists almost entirely of very long amplicons, represented by different colors, and is frequently deleted in subfertile men. Most of the AZFc amplicons have high sequence similarity with autosomal segments, indicating recent duplication and transposition to the Y chromosome. The Deleted in Azoospermia (DAZ) gene within the red-amplicon arose from an ancestral autosomal DAZ-like (DAZL) gene. It varies significantly between different men regarding to its copy number and the numbers of RNA recognition motif and DAZ repeat it encodes. We used Southern analyses to study the evolution of DAZ and AZFc amplicons on the Y chromosomes of primates. 相似文献5.
6.
Background
Recent translocations of autosomal regions to the sex chromosomes represent important systems for identifying the evolutionary forces affecting convergent patterns of sex-chromosome heteromorphism. Additions to the sex chromosomes have been reported in the melanica and robusta species groups, two sister clades of Drosophila. The close relationship between these two species groups and the similarity of their rearranged karyotypes motivates this test of alternative hypotheses; the rearranged sex chromosomes in both groups are derived through a common origin, or the rearrangements are derived through at least two independent origins. Here we examine chromosomal arrangement in representatives of the melanica and the robusta species groups and test these alternative hypotheses using a phylogenetic approach. 相似文献7.
Ying Huang Xin Wang Zhigang Cui Yuhuan Yang Yuchun Xiao Liuying Tang Biao Kan Jianguo Xu Huaiqi Jing 《BMC microbiology》2010,10(1):211
Background
Yersinia enterocolitica is an enteric pathogen that invades the intestinal mucosa and proliferates within the lymphoid follicles (Peyer's patches). The attachment invasion locus (ail) mediates invasion by Y. enterocolitica and confers an invasive phenotype upon non-invasive E. coli; ail is the primary virulence factor of Y. enterocolitica. The ferrioxamine receptor (foxA) located on the Y. enterocolitica chromosome, together with its transport protein, transports a siderophore specific for ferric ion. Currently, ail is the primary target gene for nucleic acid detection of pathogenic Y. enterocolitica. 相似文献8.
Improper chromosome synapsis is associated with elongated RAD51 structures in the maize<Emphasis Type="Italic"> desynaptic2</Emphasis> mutant 总被引:3,自引:0,他引:3
The RecA homolog, RAD51, performs a central role in catalyzing the DNA strand exchange event of meiotic recombination. During meiosis, RAD51 complexes develop on pairing chromosomes and then most disappear upon synapsis. In the maize meiotic mutant desynaptic2 (dsy2), homologous chromosome pairing and recombination are reduced by ~70% in male meiosis. Fluorescent in situ hybridization studies demonstrate that a normal telomere bouquet develops but the pairing of a representative gene locus is still only 25%. Chromosome synapsis is aberrant as exemplified by unsynapsed regions of the chromosomes. In the mutant, we observed unusual RAD51 structures during chromosome pairing. Instead of spherical single and double RAD51 structures, we saw long thin filaments that extended along or around a single chromosome or stretched between two widely separated chromosomes. Mapping with simple sequence repeat (SSR) markers places the dsy2 gene to near the centromere on chromosome 5, therefore it is not an allele of rad51. Thus, the normal dsy2 gene product is required for both homologous chromosome synapsis and proper RAD51 filament behavior when chromosomes pair. Edited by: P. Moens 相似文献
9.
S. P. Sosnikhina E. I. Mikhailova O. A. Tikholiz S. N. Priyatkina V. G. Smirnov A. V. Voilokov Yu. S. Fedotova O. L. Kolomiets Yu. F. Bogdanov 《Russian Journal of Genetics》2005,41(10):1071-1080
Genetic collection of meiotic mutants of winter rye Secale cereale L. (2n = 14) was created. Mutations were detected in inbred F2 generations after self-fertilization of the F1 hybrids, obtained by individual crossing of rye plants (cultivar Vyatka) or weedy rye with plants from autofertile lines. The mutations cause partial or complete plant sterility and are maintained in collection in a heterozygous state. Genetic analysis accompanied by cytogenetic study of meiosis has revealed six mutation types. (1) Nonallelic asynaptic mutations sy1 and sy9 caused the formation of only axial chromosome elements in prophase and anaphase. The synaptonemal complexes (SCs) were absent, the formation of the chromosome “bouquet” was impaired, and all chromosomes were univalent in meiotic metaphase I in 96.8% (sy1) and 67% (sy2) of cells. (2) Weak asynaptic mutation sy3, which hindered complete termination of synapsis in prophase I. Subterminal asynaptic segments were always observed in the SC, and at least one pair of univalents was present in metaphase I, but the number of cells with 14 univalents did not exceed 2%. (3) Mutations sy2, sy6, sy7, sy8, sy10, and sy19, which caused partially nonhomologous synapsis: change in pairing partners and fold-back chromosome synapsis in prophase I. In metaphase I, the number of univalents varied and multivalents were observed. (4) Mutation mei6, which causes the formation of ultrastructural protrusions on the lateral SC elements, gaps and branching of these elements. (5) Allelic mutations mei8 and mei8-10, which caused irregular chromatin condensation along chromosomes in prophase I, sticking and fragmentation of chromosomes in metaphase I. (6) Allelic mutations mei5 and mei10, which caused chromosome hypercondensation, defects of the division spindle formation, and random arrest of cells at different meiotic stages. However, these mutations did not affect the formation of microspore envelopes even around the cells, whose development was blocked at prophase I. Analysis of cytological pictures of meiosis in double rye mutants reveled epistatic interaction in the mutation series sy9 > sy1 > sy3 > sy19, which reflects the order of switching these genes in the course of meiosis. The expression of genes sy2 and sy19 was shown to be controlled by modifier genes. Most meiotic mutations found in rye have analogs in other plant species. 相似文献
10.
S. V. Golubtsov S. P. Sosnikhina I. V. Iordanskaya A. V. Voilokov E. I. Mikhailova O. L. Kolomiets Yu. F. Bogdanov 《Russian Journal of Genetics》2010,46(6):682-688
A study was made of the expression and inheritance of the sy11 mutation, which alters homologous chromosome synapsis in meiotic prophase I of rye. The abnormal phenotype proved to be determined
by a recessive allele of a single sy11 gene. Univalents and multivalents were observed in homozygotes for the mutant allele. Analysis of the synaptonemal complex
revealed a combination of homologous and nonhomologous synapsis in the mutant. The nonhomologous synapsis frequency significantly
decreased in the course of meiotic prophase I in the mutant. The number of chiasmata per bivalent in metaphase I was 1.1 ±
0.01 versus 1.8 ± 0.01 in wild-type plants, and the number of univalents was 2.7 ± 0.06 versus 0.5 ± 0.05 in wild-type plants.
As a result, a broad range of abnormalities was observed at subsequent stages of meiosis and led to the formation of defective
microspores. Mutant plants were semisterile. 相似文献
11.
End-to-End Association of <Emphasis Type="Italic">X</Emphasis> and <Emphasis Type="Italic">Y</Emphasis> Chromosomes in Mouse Meiosis 总被引:1,自引:0,他引:1
W. SCHNEDL 《Nature: New biology》1972,236(62):29-30
ACCORDING to the hypothesis of Crew and Koller1 and Koller and Darlington2, there are homologous segments in the X and Y chromosomes of the mouse and other mammals. The homologous regions in the mouse were believed to be localized in the extremely short arms proximal to the kinetochores. The end-to-end association at meiosis was thought to be the result of the formation of a chiasma between these homologous regions3. Electron microscopy revealed a short synaptonemal complex in mouse meiotic cells4. However, partial sex linkage has never been demonstrated in the mouse5 and other authors6–10 believe that the X and Y chromosomes associate only by connexion between the chromosome ends furthest from the centromeres. 相似文献
12.
Kitty Vijverberg Slavica Milanovic-Ivanovic Tanja Bakx-Schotman Peter J van Dijk 《BMC plant biology》2010,10(1):154
Background
DIPLOSPOROUS (DIP) is the locus for diplospory in Taraxacum, associated to unreduced female gamete formation in apomicts. Apomicts reproduce clonally through seeds, including apomeiosis, parthenogenesis, and autonomous or pseudogamous endosperm formation. In Taraxacum, diplospory results in first division restitution (FDR) nuclei, and inherits as a dominant, monogenic trait, independent from the other apomixis elements. A preliminary genetic linkage map indicated that the DIP-locus lacks suppression of recombination, which is unique among all other map-based cloning efforts of apomeiosis to date. FDR as well as apomixis as a whole are of interest in plant breeding, allowing for polyploidization and fixation of hybrid vigor, respectively. No dominant FDR or apomixis genes have yet been isolated. Here, we zoom-in to the DIP-locus by largely extending our initial mapping population, and by analyzing (local) suppression of recombination and allele sequence divergence (ASD). 相似文献13.
The chromosome morphology and meiotic pairing behavior in the pollen mother cells (PMCs) of Metasequoia glyptostroboides were investigated. The results showed that: (1) The chromosome number of the PMCs was 2n=22. (2) The PMCs developed in the successive manner, and the nucleoids in the dynamic development were similar to those of the other gymnosperms. (3) At prophase, most of the chromosomes were unable to be identified distinctively because the chromosomes were long and tangled together. The chromosome segments were paired non-synchronously. At pachytene, the interstitial or terminal regions of some bivalents did not form synapsis and the paired chromosomes showed difference in sizes, indicating that there were structure differences between the homologous chromosomes. (4) At diakinesis, the ring bivalents showed complicated configurations due to the differences in location and number of chiasmata. In addition, there were cross-linked bivalents. (5) At metaphase I, the chromosome configuration of each cell was 8.2II 0 + 1.1II + 1.3II + + 0.8I. Most of the chromosomes were ring bivalents, but some were cross-linked bivalents, rod bivalents, or univalents. (6) 15\% PMCs at anaphase I and 22\% PMCs at anaphase II presented chromosome bridges, chromosome fragments, micronuclei, and lagging chromosomes. Twenty seven percent microspores finally moved into one to three micronuclei. Twenty five percent pollens were abortive. The results indicated that the observed individual of M. glyptostroboideswas probably a parpcentric inversion heterozygote, and there were structural and behavioral differences between the homologous chromosomes. The chromosomal aberration of M. glyptostroboidesmay play an important role in the evolution of this relict species, which is known as a living fossil. Further evidence is needed to test whether the differences between homologous chromosomes were due to hybridization. 相似文献
14.
Background
Vibrio Pathogenicity Island-2 (VPI-2) is a 57 kb region present in choleragenic V. cholerae isolates that is required for growth on sialic acid as a sole carbon source. V. cholerae non-O1/O139 pathogenic strains also contain VPI-2, which in addition to sialic acid catabolism genes also encodes a type 3 secretion system in these strains. VPI-2 integrates into chromosome 1 at a tRNA-serine site and encodes an integrase intV2 (VC1758) that belongs to the tyrosine recombinase family. IntV2 is required for VPI-2 excision from chromosome 1, which occurs at very low levels, and formation of a non-replicative circular intermediate. 相似文献15.
Diogo Cavalcanti Cabral-de-Mello Rita de Cássia de Moura Maria José de Souza 《Genetica》2010,138(2):191-195
16.
María-Dolores Rey Azahara C. Martín Janet Higgins David Swarbreck Cristobal Uauy Peter Shaw Graham Moore 《Molecular breeding : new strategies in plant improvement》2017,37(8):95
Despite possessing related ancestral genomes, hexaploid wheat behaves as a diploid during meiosis. The wheat Ph1 locus promotes accurate synapsis and crossover of homologous chromosomes. Interspecific hybrids between wheat and wild relatives are exploited by breeders to introgress important traits from wild relatives into wheat, although in hybrids between hexaploid wheat and wild relatives, which possess only homoeologues, crossovers do not take place during meiosis at metaphase I. However, in hybrids between Ph1 deletion mutants and wild relatives, crossovers do take place. A single Ph1 deletion (ph1b) mutant has been exploited for the last 40 years for this activity. We show here that chemically induced mutant lines, selected for a mutation in TaZIP4-B2 within the Ph1 locus, exhibit high levels of homoeologous crossovers when crossed with wild relatives. Tazip4-B2 mutant lines may be more stable over multiple generations, as multivalents causing accumulation of chromosome translocations are less frequent. Exploitation of such Tazip4-B2 mutants, rather than mutants with whole Ph1 locus deletions, may therefore improve introgression of wild relative chromosome segments into wheat. 相似文献
17.
Background
Formation of plant root hairs originating from epidermal cells involves selection of a polar initiation site and production of an initial hair bulge which requires local cell wall loosening. In Arabidopsis the polar initiation site is located towards the basal end of epidermal cells. However little is currently understood about the mechanism for the selection of the hair initiation site or the mechanism by which localised hair outgrowth is achieved. The Arabidopsis procuste1 (prc1-1) cellulose synthase mutant was studied in order to investigate the role of the cell wall loosening during the early stages of hair formation. 相似文献18.
Samradhni S Jha Lia Danelishvili Dirk Wagner Jörg Maser Yong-jun Li Ivana Moric Steven Vogt Yoshitaka Yamazaki Barry Lai Luiz E Bermudez 《BMC microbiology》2010,10(1):100
Background
Mycobacterium avium subsp hominissuis (previously Mycobacterium avium subsp avium) is an environmental organism associated with opportunistic infections in humans. Mycobacterium hominissuis infects and replicates within mononuclear phagocytes. Previous study characterized an attenuated mutant in which the PPE gene (MAV_2928) homologous to Rv1787 was inactivated. This mutant, in contrast to the wild-type bacterium, was shown both to have impaired the ability to replicate within macrophages and to have prevented phagosome/lysosome fusion. 相似文献19.
Ayhan Kocer Iris Pinheiro Maëlle Pannetier Lauriane Renault Pietro Parma Orietta Radi Kyung-Ah Kim Giovanna Camerino Eric Pailhoux 《BMC developmental biology》2008,8(1):36