Nature and distribution of large sequence polymorphisms in Saccharomyces cerevisiae

To obtain a better understanding of the genome-wide distribution and the nature of large sequence polymorphisms (LSPs) in Saccharomyces cerevisiae, we hybridized genomic DNA of 88 haploid or homozygous diploid S. cerevisiae strains of diverse geographic origins and source substrates onto high-density tiling arrays. On the basis of loss of hybridization, we identified 384 LSPs larger than 500 bp that were located in 188 non-overlapping regions of the genome. Validation by polymerase chain reaction-amplification and/or DNA sequencing revealed that 39 LSPs were due to deletions, whereas 74 LSPs involved sequences diverged far enough from the S288c reference genome sequence as to prevent hybridization to the microarray features. The LSP locations were biased toward the subtelomeric regions of chromosomes, where high genetic variation in genes involved in transport or fermentation is thought to facilitate rapid adaptation of S. cerevisiae to new environments. The diverged LSP sequences appear to have different allelic ancestries and were in many cases identified as Saccharomyces paradoxus introgressions.