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Results for “polyploidization”

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At least 613 records · Page 34Linked to original sources
PubMed2000

Intergenomic translocations of polyploid oats (genus Avena) revealed by genomic in situ hybridization.

Wild and cultivated hexaploid oats share the same genomes (AACCDD) and display a considerable level of interspecific variation in both plant and chromosome morphology. The GISH was utilized to detect the interspecific genomic compositions in four hexaploid and two tetraploid oats using total genomic DNA of Avena eriantha (a C-genome diploid) as probe. Intergenomic translocations between A/D and C-genome chromosomes were frequently observed in hexaploid and tetraploid species. In the hexaploid, two pairs of A/D genome segments on C-genome chromosome (A/D-C) translocation and four to six pairs of C-genome segments on A/D genome chromosome (C-A/D) translocation were clearly identified whilst the number of A/D-C translocations was constant among species. In the tetraploid A. maroccana (AACC), a pair of A-C and four pairs of C-A translocations were observed. Moreover, the A/D translocation segments on chromosome 5C was detected only in A. byzantina and A. maroccana, whilst A/D-C translocations were observed on the 1C and 7C of A. sativa, A. fatua and A. sterilis. A. byzantina did however also carry the 1C rearrangement. This result shows that A. byzantina has retained a similar genomic constitution to the tetraploid ancestor of hexaploid oats, A. maroccana. Three pairs of A-C translocations were detected only in A. murphyi (AACC), and two pairs of those were the 1C and 7C as well as the three hexaploid species except A. byzantina.

Avena↗
PubMed2006

The obligate human pathogen, Neisseria gonorrhoeae, is polyploid.

We show using several methodologies that the Gram-negative, diplococcal-bacterium Neisseria gonorrhoeae has more than one complete genome copy per cell. Gene dosage measurements demonstrated that only a single replication initiation event per chromosome occurs per round of cell division, and that there is a single origin of replication. The region containing the origin does not encode any genes previously associated with bacterial origins of replication. Quantitative PCR results showed that there are on average three genome copies per coccal cell unit. These findings allow a model for gonococcal DNA replication and cell division to be proposed, in which a minimum of two chromosomal copies exist per coccal unit within a monococcal or diplococcal cell, and these chromosomes replicate in unison to produce four chromosomal copies during cell division. Immune evasion via antigenic variation is an important mechanism that allows these organisms to continually infect a high risk population of people. We propose that polyploidy may be necessary for the high frequency gene conversion system that mediates pilin antigenic variation and the propagation of N. gonorrhoeae within its human hosts.

DNA, Bacterial↗
PubMed2004

Conditioned medium increases the polyploid cell composition of bovine somatic cell nuclear-transferred blastocysts.

The effects of bovine cumulus cell-conditioned medium on cloned bovine embryonic development and subsequent chromosome complement were examined using an air-dry procedure. Conditioned media were prepared using CR1aa supplemented with either fetal bovine serum (FBS) or bovine serum albumin (BSA). Nuclear-transferred embryos were reconstructed with nuclei from cumulus cells. Similar cleavage, morula, and blastocyst development was observed in conditioned media groups compared with the co-culture group. No differences (P > 0.05) were observed in the composition of blastocyst chromosomes after co-culture in different media, either with or without starvation of donor cells. The overall diploid blastocyst rate ranged from 75% to 84%. Chromosomal complement of blastocysts, however, was very different between conditioned medium and co-culture treatments. Overall incidence of chromosomal anomalies was 40% in conditioned medium, which was significantly higher (P < 0.001) than the co-culture group (20%). Moreover, a higher incidence (P < 0.05) of chromosomally abnormal blastocysts (41.5%) was observed after culture with FBS-containing conditioned medium than those cultured in BSA-containing conditioned medium (31.4%). No diploid improvement was observed after exchange of the culture system from conditioned medium to co-culture, or from co-culture to conditioned medium after the first 72 h of culture. The results of this study also indicated that the overall cell number was much lower (P < 0.01) in blastocysts with chromosomal abnormalities than those with a normal diploid state. We have concluded that medium conditioned with bovine cumulus cells increases the incidence of chromosomal anomalies in nuclear reconstructed embryos.

Animals↗
PubMed2004

Sequence polymorphism in polyploid wheat and their d-genome diploid ancestor.

Sequencing was used to investigate the origin of the D genome of the allopolyploid species Triticum aestivum and Aegilops cylindrica. A 247-bp region of the wheat D-genome Xwye838 locus, encoding ADP-glucopyrophosphorylase, and a 326-bp region of the wheat D-genome Gss locus, encoding granule-bound starch synthase, were sequenced in a total 564 lines of hexaploid wheat (T. aestivum, genome AABBDD) involving all its subspecies and 203 lines of Aegilops tauschii, the diploid source of the wheat D genome. In Ae. tauschii, two SNP variants were detected at the Xwye838 locus and 11 haplotypes at the Gss locus. Two haplotypes with contrasting frequencies were found at each locus in wheat. Both wheat Xwye838 variants, but only one of the Gss haplotypes seen in wheat, were found among the Ae. tauschii lines. The other wheat Gss haplotype was not found in either Ae. tauschii or 70 lines of tetraploid Ae. cylindrica (genomes CCDD), which is known to hybridize with wheat. It is concluded that both T. aestivum and Ae. cylindrica originated recurrently, with at least two genetically distinct progenitors contributing to the formation of the D genome in both species.

Base Sequence↗
PubMed2005

A Bayesian approach for discriminating among alternative inheritance hypotheses in plant polyploids: the allotetraploid origin of genus Borderea (Dioscoreaceae).

Polyploidy is a common phenomenon occurring in a vast number of land plants. Investigations of patterns of inheritance and the origins of plants (i.e., autopolyploidy vs. allopolyploidy) usually involve cytogenetic and molecular studies of chromosome pairing, chromosome mapping, and marker segregation analysis through experimental crosses and progeny tests. Such studies are missing for most wild species, for which artificial crosses are difficult, not feasible, or unaffordable. We report here a Bayesian method to discriminate between alternative inheritance patterns in the two extant, tetraploid species of the monocot genus Borderea (Dioscoreaceae), which does not involve progeny array tests. Our approach is based on the screening of a large number of SSR genotypes, which were obtained from successful amplifications of 17 microsatellite regions in individuals of both B. chouardii and B. pyrenaica. We tested for tetrasomic vs. disomic modes of inheritance, using the Bayes factor test. Assignment of genotypes under both alternatives could be unequivocally done for 14 and 11 of the 17 studied microsatellite regions in B. chouardii and B. pyrenaica, respectively, totaling 9502 analyzed genotypes. The comparison of posterior probabilities for the two competing hypotheses across the surveyed loci clearly favored a disomic inheritance pattern. Linkage tests indicated that none of the studied SSR loci were in linkage disequilibrium, thus representing independent samples of the Borderea genome. These results, along with previous allozyme data, support the allotetraploid origin of this paleoendemic genus and reveal the lowest reported chromosome base number for the family of the yams.

Bayes Theorem↗
PubMed2006

Evolution of hypervariable microsatellites in apomictic polyploid lineages of Ranunculus carpaticola: directional bias at dinucleotide loci.

Microsatellites are widely used in genetic and evolutionary analyses, but their own evolution is far from simple. The mechanisms maintaining the mutational patterns of simple repeats and the typical stable allele-frequency distributions are still poorly understood. Asexual lineages may provide particularly informative models for the indirect study of microsatellite evolution, because their genomes act as complete linkage groups, with mutations being the only source of genetic variation. Here, we study the direction of accumulated dinucleotide microsatellite mutations in wild asexual lineages of hexaploid Ranunculus carpaticola. Whereas the overall number of contractions is not significantly different from that of expansions, the within-locus frequency of contractions, but not of expansions, significantly increases with allele length. Moreover, within-locus polymorphism is positively correlated with allele length, but this relationship is due solely to the influence of contraction mutations. Such asymmetries may explain length constraints generally observed with microsatellites and are consistent with stable, bell-shaped allele-frequency distributions. Although apomictic and allohexaploid, the R. carpaticola lineages show mutational patterns resembling the trends observed in a broad range of organisms, including sexuals and diploids, suggesting that, even if not of germline origin, the mutations in these apomicts may be the consequence of similar mechanisms.

Cell Lineage↗
PubMed2000

Morphological comparisons and hypotheses on the origin of polyploids in parthenogenetic Fasciola sp.

It is known that Fasciola sp. from Japan and the Republic of Korea consist of diploids (2n = 2x = 20), triploids (2n = 3x = 30), and mixoploids with diploid and triploid cells. Triploids are distributed over Asia and Hawaii. Abnormal spermatogenesis and parthenogenetic reproduction are the main characteristics of Fasciola sp. Here we measured 21 different morphological parameters of diploid and triploid flukes of Fasciola sp. obtained from Japan and the Republic of Korea. Statistical analysis showed that diploid and triploid flukes were morphologically different. No bivalents or trivalents could be detected in diploid and triploid flukes, respectively. Based on our findings, we speculate that parthenogenetic diploids, triploids, and mixoploids (2x/3x) of Fasciola sp. are genetically related to each other.

Animals↗
PubMed1976

Polyploidization in rat liver: the role of binucleate cells.

Liver cells were isolated from rats undergoing active formation of tetraploid cells and prelabelled in their DNA with 14C thymidine. Autoradiography of the isolated cells showed that binucleate diploid cells, a major component of the parenchymal cell population at this time, are also active in DNA synthesis. These cells probably pass through mitosis and generate mononucleate tetraploid cells, the dominant cell type of mature rat liver, since the frequency of binucleate tetraploid cells is very low at this stage in rat liver development. The biological significance of liver polyploidy is discussed and it is suggested that this lies in enhanced resistance to mutagenesis.

Animals↗