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Results for “polyploid establishment”

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At least 19 recordsLinked to original sources
PubMed2005

The effect of self-fertilization, inbreeding depression, and population size on autopolyploid establishment.

The minority cytotype exclusion principle describes how random mating between diploid and autotetraploid cytotypes hinders establishment of the rare cytotype. We present deterministic and stochastic models to ascertain how selfing, inbreeding depression, unreduced gamete production, and finite population size affect minority cytotype exclusion and the establishment of autotetraploids. Results demonstrate that higher selfing rates and lower inbreeding depression in autotetraploids facilitate establishment of autotetraploid populations. Stochastic effects due to finite population size increase the probability of polyploid establishment and decrease the mean time to tetraploid fixation. Our results extend the minority cytotype exclusion principle to include important features of plant reproduction and demonstrate that variation in mating system parameters significantly influences the conditions necessary for polyploid establishment.

Computer Simulation↗
PubMed2003

Outcrossing rate and inbreeding depression in the herbaceous autotetraploid, Campanula americana.

Polyploidy in angiosperms is frequently associated with an increase in self-compatibility. Self-fertilization can enhance polyploid establishment, and theory predicts reduced inbreeding depression in polyploids relative to diploids. Therefore, we may expect mating systems that promote self-fertilization or mixed-mating in polyploid species. However, few studies have measured polyploid mating systems and inbreeding depression. We report the outcrossing rate and inbreeding depression for Campanula americana, a self-compatible protandrous herb. Allozyme genotypes suggest that C. americana is an autotetraploid with tetrasomic inheritance. We found that the multilocus outcrossing rate, t(m)=0.938, did not differ from unity. This result was unexpected since previous work demonstrated that pollinators frequently move from male- to female-phase flowers on the same plant, that is, geitonogamy. Self and outcross pollinations were conducted for three populations. Offspring were germinated in controlled conditions and grown to maturity in pots in nature. Inbreeding depression was not significant for most seed and germination characters. However, all later life traits except flowering date differed between inbred and outcrossed individuals resulting in a 26% reduction in cumulative fitness for inbred plants. Limited early- and moderate later-life inbreeding depression suggest that it is buffered by the higher levels of heterozygosity found in an autotetraploid. C. americana appears to have a flexible mating system where within flower protandry and/or cryptic self-incompatibility result in a high outcrossing rate when pollinators are abundant, but self-compatibility and limited inbreeding depression maintain reproductive success when mates are limited.

Campanulaceae↗
PubMed1999

Evolutionary consequences of diploid-polyploid hybrid zones in wild species.

Hybrid zones between cytotypes with different ploidy levels are particularly interesting for studying the ecology and the evolution of reproductive interactions between closely related taxa. Diploid-polyploid hybrid zones differ fundamentally from those between diploids in that they reflect certain conditions that are characteristic of the early stage of polyploid establishment, and allow tests of hypotheses relating to the dynamics and evolution of polyploid complexes. Recent theoretical and empirical studies have provided important data on the evolution of isolating mechanisms in diploid-polyploid contact zones, but have also shown that introgression might counteract the evolution of isolating mechanisms.

Journal Article↗
PubMed2005

Methods for genome-wide analysis of gene expression changes in polyploids.

Polyploidy is an evolutionary innovation, providing extra sets of genetic material for phenotypic variation and adaptation. It is predicted that changes of gene expression by genetic and epigenetic mechanisms are responsible for novel variation in nascent and established polyploids (Liu and Wendel, 2002; Osborn et al., 2003; Pikaard, 2001). Studying gene expression changes in allopolyploids is more complicated than in autopolyploids, because allopolyploids contain more than two sets of genomes originating from divergent, but related, species. Here we describe two methods that are applicable to the genome-wide analysis of gene expression differences resulting from genome duplication in autopolyploids or interactions between homoeologous genomes in allopolyploids. First, we describe an amplified fragment length polymorphism (AFLP)--complementary DNA (cDNA) display method that allows the discrimination of homoeologous loci based on restriction polymorphisms between the progenitors. Second, we describe microarray analyses that can be used to compare gene expression differences between the allopolyploids and respective progenitors using appropriate experimental design and statistical analysis. We demonstrate the utility of these two complementary methods and discuss the pros and cons of using the methods to analyze gene expression changes in autopolyploids and allopolyploids. Furthermore, we describe these methods in general terms to be of wider applicability for comparative gene expression in a variety of evolutionary, genetic, biological, and physiological contexts.

Arabidopsis↗
PubMed2003

Octaploid Meth-A cells are established from a highly polyploidized cell population.

Tetraploid Meth-A cells were polyploidized by demecolcin, an inhibitor of spindle fibre formation in M phase, and then released from the drug 1, 2, 3 and 4 days after the addition. Octaploid cells were successfully established from cell populations including hexadecaploid cells produced by 2, 3 and 4 days of exposure to demecolcin. One-day-treated cells were polyploidized octaploid cells, but they returned to tetraploid cells. All of the octaploid Meth-A cells showed essentially the same features. The octaploid Meth-A cells had eight homologous chromosomes and double the DNA content of the parent tetraploid cells. The doubling time of octaploid Meth-A cells was 30.2 h, somewhat longer than the 28.3 and 24.0 h of tetraploid and diploid cells, respectively. The fractions of cells in the G1, S and G2/M phases were essentially the same in diploid, tetraploid and octaploid Meth-A cells. The cell volume of octaploid Meth-A cells was about two times that of the tetraploid cells. It was concluded that octaploid Meth-A cells were established from transient hexadecaploid cells produced by the polyploidization of tetraploid cells that had been established from diploid cells.

Animals↗
PubMed2001

Establishment of a tetraploid Meth-A cell line through polyploidization by demecolcine but not by staurosporine, K-252A and paclitaxel.

Polyploid cells are made by DNA reduplication without cell division, however, it is not easy to establish polyploid mammalian cell lines. It is worth studying the difference in cell character between hyperploid and parent cell lines. Meth-A cells were polyploidized by demecolcine, K-252a, staurosporine and paclitaxel. The cell-cycle responses of highly polyploid Meth-A cells after the removal of the drugs were examined by flow cytometry (FCM). Meth-A cells were highly polyploidized by these drugs. The polyploid Meth-A cells gradually decreased in ploidy after the drug release. A tetraploid Meth-A cell line was established only from the demecolcine-induced polyploid Meth-A cells. The duration of G1, S and G2/M phases of the tetraploid cell line were mostly the same as those of the parent diploid cells, except that the G2/M phase was 1.5 h longer. The chromosome number of tetraploid Meth-A cell line was about twice of the diploidy. A tetraploid Meth-A cell line was established.

Animals↗
PubMed2001

Fecundity and offspring ploidy in matings among diploid, triploid and tetraploid Chamerion angustifolium (Onagraceae): consequences for tetraploid establishment.

Models of polyploid evolution indicate that tetraploids are more likely to establish within diploid populations when they are formed recurrently through the union of unreduced (n=2n) gametes. To account for the coexistence of diploids and tetraploids in populations of Chamerion angustifolium, diploid, triploid and tetraploid plants were crossed in all possible combinations and fecundity and ploidy using flow cytometry of the resulting progeny were measured. Combined with previous data on cytotype fitness, these data were used in a simulation to examine the impact of unreduced gametes on tetraploid evolution. Seed set per fruit was highest in 2x x 2x crosses (69%), intermediate in 4x x 4x, 2x x 4x and 3x x 4x crosses (range, 11-35%) and lowest in 3x x 2x and 3x x 3x crosses (range, 1-10%). Offspring were diploid (94%) or triploid (6%) in 2x x 2x crosses, diploid (17.5%), triploid (56%) or tetraploid (26.5%) in 3x x 2x crosses, and triploid (53%) and tetraploid (44%) in all others (4x x 4x, 3x x 4x, 2x x 4x), indicating that some gametes are unreduced, particularly in triploids. Forty-two percent of offspring, from three different crosses, had DNA contents greater than tetraploids. Computer simulations based on these results showed that unreduced gamete formation via triploids in C. angustifolium can promote the coexistence of diploids and tetraploids, but, due to law triploid fitness, is insufficient to overcome tetraploid minority disadvantage.

Computer Simulation↗
PubMed1987

Establishment and characterization of a polyploid mouse myeloid leukemia cell line useful for in-vivo examination of cell proliferation kinetics.

A near-tetraploid cell line (LL-1) was established from mouse myeloid leukemia Ml cells. This paper reports characterization of the LL-1 cells and the in-vivo detection of the leukemia cells transplanted in syngeneic mice. The LL-1 cells are myeloblastic and grow well in suspension culture. Morphological analysis showed that the nucleus of LL-1 cells was almost twice as large as that of the parent line cells. The modal chromosome number of LL-1 cells was 75, and the DNA index determined by flow cytometry was 2.3. The cells were unresponsive to the inducer of differentiation of M1 cells. Transplantation experiments showed that the LL-1 cells were leukemogenic in syngeneic SL mice: ten mice inoculated i.p. with LL-1 cells (4 X 10(6)) all died of leukemia within 6 weeks. The cells in the peritoneal cavity were collected at appropriate times during progression of the leukemia. On microscopic examination the LL-1 cells were clearly distinguishable from normal host cells in the peritoneal cavity by the size of their nucleus. Counts showed that their number decreased markedly during the first 2 weeks after their transplantation, and then increased about ten times in a week. By 4 or 5 weeks after transplantation these LL-1 cells filled the peritoneal cavity. These large-sized leukemia cells that grow in syngeneic mice will be useful for investigating the mechanisms of in-vivo responses of leukemia cells to various therapeutic treatments.

Animals↗
PubMed1999

Population cytotype structure in the polyploid galax urceolata (Diapensiaceae)

The geographical distributions of diploid and polyploid Galax urceolata overlap in the Blue Ridge Mountains, USA. As part of an investigation into the evolutionary forces governing the establishment of polyploids and their coexistence with diploids, we examined the population frequencies of diploids, triploids and tetraploids in the area of overlap. Ploidy was inferred from estimates of DNA content, using flow cytometry, for 1570 individuals sampled from 42 populations. Across the entire sampling area, diploids and tetraploids were most abundant (55% and 34% of individuals, respectively), whereas triploids were least abundant (11%). Cytotype frequencies differed significantly among the northern, central and southern regions of the range (G = 649.02, d.f. = 4, P < 0.0001), with diploids most frequent in the north-east and least frequent in the south-west. Twenty-six per cent of the populations contained three cytotypes, 33% contained two, and 40% had a single cytotype. Populations with two cytotypes occurred in all possible cytotype combinations, but when triploids were present, they were always in the minority. Uniform populations were either diploid (81%) or tetraploid (19%), but never triploid. Overall, populations are predominantly diploid or tetraploid but rarely evenly mixed, suggesting disruptive selection for chromosome number in G. urceolata. The contribution of ecological sorting and frequency-dependent mating success to the distribution of polyploids and diploids is discussed.

Journal Article↗
PubMed2006

Pollinator-mediated assortative mating in mixed ploidy populations of Chamerion angustifolium (Onagraceae).

Establishment of polyploid individuals within diploid populations is theoretically unlikely unless polyploids are reproductively isolated, pre-zygotically, through assortative pollination. Here, we quantify the contribution of pollinator diversity and foraging behaviour to assortative pollen deposition in three mixed-ploidy populations of Chamerion angustifolium (Onagraceae). Diploids and tetraploids were not differentiated with respect to composition of insect visitors. However, foraging patterns of the three most common insect visitors (all bees) reinforced assortative pollination. Bees visited tetraploids disproportionately often and exhibited higher constancy on tetraploids in all three populations. In total, 73% of all bee flights were between flowers of the same ploidy (2x-2x, 4x-4x); 58% of all flights to diploids and 83% to tetraploids originated from diploid and tetraploid plants, respectively. Patterns of pollen deposition on stigmas mirrored pollinator foraging behaviour; 73% of all pollen on stigmas (70 and 75% of pollen on diploid and tetraploid stigmas, respectively) came from within-ploidy pollinations. These results indicate that pollinators contribute to high rates of pre-zygotic reproductive isolation. If patterns of fertilization track pollen deposition, pollinator-plant interactions may help explain the persistence and spread of tetraploids in mixed-ploidy populations.

Alberta↗
PubMed2026

Ancient polyploidization waves as evolutionary shields for angiosperms.

Chen et al. identified 132 whole-genome duplications (WGDs) clustered around environmental crises. We highlight how, over longer evolutionary timescales, ancient WGDs convergently retained MADS-box, MYB, WRKY and HSF transcription factors, building stress-adaptation networks. These insights guide climate-resilient crop improvement through comparative genomics and CRISPR engineering.

MADS-box↗
PubMed1999

The influence of triploidy on gene expression in the silkworm, bombyx mori

In Bombyx mori, it is well established that polyploids are easily induced when newly laid eggs are exposed to a variety of conditions, such as high or low temperature, centrifugal force, or chemicals like colchicine. To investigate gene dosage effects by varying the ploidy, the transcription levels of six genes expressed in various tissues were analysed in the diploid and two different genetically produced triploids (PPC and CCP). In the PPC triploid, the transcription level per cell of two genes was directly proportional to the structural gene dosage, whereas two other genes showed the mRNA level expected if compensation occurred. In the CCP triploid, three genes displayed dose-dependent levels of expression, whereas one gene showed the same expression level as the diploid strains. In both triploids, exceptional cases showed a negative correlation of expression with ploidy or a positive correlation greater than expected from the structural gene dosage. Interestingly, the transcription levels of most tested genes were significantly different from the strains which were used as parents of the triploids, and also widely divergent expression patterns were found for some genes in the diploid offspring. In this study, the cause of the unexpected expression patterns observed in the euploid series is discussed in relation to the difference between the two parental strains in expression level of genes and in trans-acting regulatory effects on their target genes.

Journal Article↗
PubMed2004

Evolutionary dynamics and preferential expression of homeologous 18S-5.8S-26S nuclear ribosomal genes in natural and artificial glycine allopolyploids.

Polyploidy is an important evolutionary process in plants, but much remains to be learned about the evolution of gene expression in polyploids. Evolution and expression of the 18S-5.8S-26S ribosomal gene family was investigated at homeologous loci in the Glycine subgenus Glycine perennial soybean polyploid complex, which consists of several diploid genomes that have formed allopolyploids in various combinations, often recurrently. A semiquantitative PCR method targeting the internal transcribed spacer (ITS) of the 18S-5.8S-26S nuclear ribosomal DNA (nrDNA) was used to survey the ratio between homeologous repeats in polyploid genomes and to test for preferential expression of homeologous nrDNA loci. Most natural polyploids possess one predominant nrDNA homeolog in their genome. Analysis of F2 segregation in an artificial cross suggested that in some plants, most or all repeats at one homeologous locus have been lost, whereas in other plants two loci remain, but both have been homogenized by concerted evolution. In most natural allopolyploids harboring a relatively balanced ratio of homeologs, one homeolog was expressed preferentially, but in the majority of plants, low levels of transcription could be detected from the other homeolog. Individuals within some tetraploid taxa varied as to which homeolog was expressed preferentially. In some plants, the degree of preferential expression also varied among tissues. Preferential expression was absent in synthetic polyploids and in some artificial diploid hybrids, suggesting that nucleolar dominance is not necessarily a direct result of hybridization or polyploidization. The establishment of preferential expression in Glycine allopolyploids appears to be either stochastic within lineages or genotype specific.

DNA, Ribosomal↗
PubMed1993

Hepatic nuclear ploidy distribution of dietary-restricted mice.

Hepatic parenchymal cells in most adult mammals are polyploid, with most of the cells in the quiescent or low-proliferation state. Polyploidization has been related to carcinogenesis and aging, and both end points are significantly affected by dietary restriction (DR). Direct measures of hepatic nuclear polyploidization in DR B6C3F1 mice have not been examined. We examined the effect of DR on distributions of nuclear ploidy in both sexes and on different age groups of B6C3F1 mice. Differences between young and old male mice and between old male and female mice were also compared. Hepatic nuclear ploidy values were measured by flow cytometry. The DNA histograms were analyzed for the percentage of nuclei having different classes of DNA content by gating channels between the areas under the peaks of diploid, tetraploid, and octaploid. The results indicate that 1 or 26 months of DR started at 4 months of age did not alter hepatic nuclear ploidy distributions in young and old mice. Our data suggest that in the male mouse, polyploidization is established by 5 months of age for hepatic nuclei and that ploidy classes are affected by sex at 30 months of age. For females, effects in the octaploid nuclei are seen as a result of DR.

Age Factors↗
PubMed2002

Establishment of a triploid V79 cell line from tetraploid cells obtained through polyploidization using K-252a.

Triploid V79 cells were established from tetraploid cells. Diploid V79 cells were polyploidized by K-252a, an inhibitor of protein kinases, and then released from the drug for 10 days. At that time, the cell population was a mixture of diploid and tetraploid cells. Triploid cells were obtained through the cloning of tetraploid cells. They had 33 chromosomes (1.5 times the diploid number) and showed a karyotype of three homologueous chromosomes. The duration of the G1, S and G2/M phases was almost the same as for diploid cells. The cell volume of triploid V79 cells was about two times that of the diploid cells. An explanation for the diploid-tetraploid-triploid transition is proposed.

Animals↗
PubMedDate not supplied

Novel flowering time variation in the resynthesized polyploid Brassica napus.

Recent molecular data using resynthesized polyploids of Brassica napus established that genome changes can occur rapidly after polyploid formation. In this study we present data that de novo phenotypic variation for flowering time also occurs rapidly after polyploidization. Two initial polyploid plants were developed by reciprocal crosses of B. rapa and B. oleracea followed by chromosome doubling to establish two lineages, each of which was expected to be homozygous and homogeneous. Several sublineages of each lineage were advanced by self-pollination. The range in days to flower of the sixth generation plants was 39-75 and 43-64 for the two lineages. Analysis of seventh generation progeny indicated that the variation was heritable. Lines were selected and self-pollinated to the eighth generation and also testcrossed to a natural B. napus cultivar; the testcross plants were then self-pollinated. Differences in flowering time were also inherited in these advanced generations. Days to flower was significantly correlated with leaf number in each generation. The rapid evolution of new phenotypic variation, like that observed in this model system, may have contributed to the success and diversification of natural polyploid organisms.

Brassica↗
PubMed2001

Polyploidy alters advertisement call structure in gray treefrogs.

Whole-genome duplication is believed to have played a significant role in the early evolution and diversification of vertebrate animals. The establishment of newly arisen polyploid lineages of sexually reproducing animals requires assortative mating between polyploids. Here, we show that genome duplication can directly alter a phenotypic trait mediating mate choice in the absence of genotypic change. Our results suggest that the direct effect of polyploidy on behaviour is a consequence of increased cell size.

Animals↗