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Mol Biol Evol. 2015 Jan;32(1):184-92. doi: 10.1093/molbev/msu295. Epub 2014 Oct 27.

Population genomics reveals chromosome-scale heterogeneous evolution in a protoploid yeast.

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Department of Genetics, Genomics and Microbiology, Université de Strasbourg/CNRS, UMR7156, Strasbourg, France.
Sorbonne Universités, UPMC Université Paris 06, UMR 7238, Biologie Computationnelle et Quantitative, Paris, France CNRS, UMR7238, Biologie Computationnelle et Quantitative, Paris, France
Department of Genetics, Genomics and Microbiology, Université de Strasbourg/CNRS, UMR7156, Strasbourg, France


Yeast species represent an ideal model system for population genomic studies but large-scale polymorphism surveys have only been reported for species of the Saccharomyces genus so far. Hence, little is known about intraspecific diversity and evolution in yeast. To obtain a new insight into the evolutionary forces shaping natural populations, we sequenced the genomes of an expansive worldwide collection of isolates from a species distantly related to Saccharomyces cerevisiae: Lachancea kluyveri (formerly S. kluyveri). We identified 6.5 million single nucleotide polymorphisms and showed that a large introgression event of 1 Mb of GC-rich sequence in the chromosomal arm probably occurred in the last common ancestor of all L. kluyveri strains. Our population genomic data clearly revealed that this 1-Mb region underwent a molecular evolution pattern very different from the rest of the genome. It is characterized by a higher recombination rate, with a dramatically elevated A:T → G:C substitution rate, which is the signature of an increased GC-biased gene conversion. In addition, the predicted base composition at equilibrium demonstrates that the chromosome-scale compositional heterogeneity will persist after the genome has reached mutational equilibrium. Altogether, the data presented herein clearly show that distinct recombination and substitution regimes can coexist and lead to different evolutionary patterns within a single genome.


chromosome evolution; population genomics; yeast

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