Molecular-Genetic Biodiversity in a Natural Population of the Yeast<i>Saccharomyces cerevisiae</i>From “Evolution Canyon”: Microsatellite Polymorphism, Ploidy and Controversial Sexual Status

Ezov, Tal Katz; Boger-Nadjar, E.; Frenkel, Zeev; Katsperovski, I.; Kemeny, Stav; Nevo, Eviatar; Korol, Abraham B.; Kashi, Yechezkel

doi:10.1534/genetics.106.062745

Cited by 92 publications

(92 citation statements)

References 95 publications

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“…14 and unpublished observations). By contrast, S. cerevisiae strains are often heterothallic [i.e., unable to undergo mating type switching (39)]. Haplo-selfing presumably results from a failure to mate during spore germination, for example if one or more of the meiotic products are inviable, resulting in a ''lonely spore'', or if the spores are separated before germination.…”

Section: Discussionmentioning

confidence: 99%

Population genomics of the wild yeast Saccharomyces paradoxus : Quantifying the life cycle

Tsai

Bensasson

Burt

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

296

321

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Most microbes have complex life cycles with multiple modes of reproduction that differ in their effects on DNA sequence variation. Population genomic analyses can therefore be used to estimate the relative frequencies of these different modes in nature. The life cycle of the wild yeast Saccharomyces paradoxus is complex, including clonal reproduction, outcrossing, and two different modes of inbreeding. To quantify these different aspects we analyzed DNA sequence variation in the third chromosome among 20 isolates from two populations. Measures of mutational and recombinational diversity were used to make two independent estimates of the population size. In an obligately sexual population these values should be approximately equal. Instead there is a discrepancy of about three orders of magnitude between our two estimates of population size, indicating that S. paradoxus goes through a sexual cycle approximately once in every 1,000 asexual generations. Chromosome III also contains the mating type locus (MAT), which is the most outbred part in the entire genome, and by comparing recombinational diversity as a function of distance from MAT we estimate the frequency of matings to be Ϸ94% from within the same tetrad, 5% with a clonemate after switching the mating type, and 1% outcrossed. Our study illustrates the utility of population genomic data in quantifying life cycles. mating systems ͉ inbreeding ͉ sex ͉ nucleotide polymorphism ͉ linkage disequilibrium M icrobial life cycles are often difficult to study because the organisms involved are so small. Laboratory studies can reveal what a species is capable of doing, but give little information on the frequencies of different modes of reproduction in nature. Instead, we must look at patterns of DNA sequence variation to infer the reproductive system. Pioneered by studies in bacteria, genealogical analyses have been very fruitful in uncovering sex where sexual stages had not been seen, and cryptic species where only one taxon had been recorded (1-4). Quantifying the different aspects of the life cycle, however, has been difficult. Population genomic data now allow accurate measures of mutational and recombinational diversity, and theory predicts that these parameters can be used to estimate the frequencies of different modes of reproduction in the life cycle, including frequencies of sex, outcrossing, and various forms of inbreeding.The bakers' yeast Saccharomyces cerevisiae has long been a model system in genetics and cell biology; more recently, together with its undomesticated relatives Saccharomyces paradoxus and Saccharomyces cariocanus, it is also becoming a focus of studies in ecology and evolution (5-7). Laboratory studies indicate that when conditions are good the primary mode of reproduction is vegetative budding of diploid cells. Starvation induces meiosis, each diploid cell producing a tetrad of haploid spores of two different mating types (a and ␣), enclosed within an ascus (8). When conditions improve, the spores germinate and are constitutively ready to...

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Section: Discussionmentioning

confidence: 99%

Population genomics of the wild yeast Saccharomyces paradoxus : Quantifying the life cycle

Tsai

Bensasson

Burt

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

296

321

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“…Triploid yeast strains have been observed in the wild (Ezov et al 2006) and have been generated in the lab by forced matings between haploids and diploids (Pomper et al 1954). Since diploids of the MATa/MATa genotype do not mate, it is likely that the forced matings selected for rare diploids that had become homozygous for MATa or MATa as a consequence of a mitotic recombination at the mating-type locus on chromosome III.…”

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confidence: 99%

Meiotic Chromosome Segregation in Triploid Strains of Saccharomyces cerevisiae

2010

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Meiosis in triploids results in four highly aneuploid gametes because six copies of each homolog must be segregated into four meiotic products. Using DNA microarrays and other physical approaches, we examined meiotic chromosome segregation in triploid strains of Saccharomyces cerevisiae. In most tetrads with four viable spores, two of the spores had two copies of a given homolog and two spores had only one copy. Chromosomes segregated randomly into viable spores without preferences for generating near haploid or near diploid spores. Using single-nucleotide polymorphisms, we showed that, in most tetrads, all three pairs of homologs recombined. Strains derived from some of the aneuploid spore colonies had very high frequencies of mitotic chromosome loss, resulting in genetically diverse populations of cells.

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“…Natural variation for ploidy exists in Saccharomyces cerevisiae, with haploids, diploids, and tetraploids endemic to the same microsite, suggesting that ploidy variation could play an adaptive role (Ezov et al 2006). The ploidy state flexibility of yeast allows the study of strains that are genetically identical except for ploidy, a useful tool for directly plumbing the effects of WGD in evolving populations (Galitski et al 1999).…”

Section: Fungimentioning

confidence: 99%

Genome management and mismanagement—cell-level opportunities and challenges of whole-genome duplication

Yant

Bomblies

2015

Genes Dev.

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Whole-genome duplication (WGD) doubles the DNA content in the nucleus and leads to polyploidy. In whole-organism polyploids, WGD has been implicated in adaptability and the evolution of increased genome complexity, but polyploidy can also arise in somatic cells of otherwise diploid plants and animals, where it plays important roles in development and likely environmental responses. As with whole organisms, WGD can also promote adaptability and diversity in proliferating cell lineages, although whether WGD is beneficial is clearly context-dependent. WGD is also sometimes associated with aging and disease and may be a facilitator of dangerous genetic and karyotypic diversity in tumorigenesis. Scaling changes can affect cell physiology, but problems associated with WGD in large part seem to arise from problems with chromosome segregation in polyploid cells. Here we discuss both the adaptive potential and problems associated with WGD, focusing primarily on cellular effects. We see value in recognizing polyploidy as a key player in generating diversity in development and cell lineage evolution, with intriguing parallels across kingdoms.

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Molecular-Genetic Biodiversity in a Natural Population of the YeastSaccharomyces cerevisiaeFrom “Evolution Canyon”: Microsatellite Polymorphism, Ploidy and Controversial Sexual Status

Cited by 92 publications

References 95 publications

Population genomics of the wild yeast Saccharomyces paradoxus : Quantifying the life cycle

Population genomics of the wild yeast Saccharomyces paradoxus : Quantifying the life cycle

Meiotic Chromosome Segregation in Triploid Strains of Saccharomyces cerevisiae

Genome management and mismanagement—cell-level opportunities and challenges of whole-genome duplication

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