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

Isheng J. Tsai, Douda Bensasson, Austin Burt, Vassiliki Koufopanou

    Research output: Contribution to journalArticlepeer-review

    Abstract

    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 ≈94% 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. © 2008 by The National Academy of Sciences of the USA.
    Original languageEnglish
    Pages (from-to)4957-4962
    Number of pages5
    JournalProceedings of the National Academy of Sciences of the United States of America
    Volume105
    Issue number12
    DOIs
    Publication statusPublished - 25 Mar 2008

    Keywords

    • Inbreeding
    • Linkage disequilibrium
    • Mating systems
    • Nucleotide polymorphism
    • Sex

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