Abstract #56

Independent sorting-out of gene pairs formed by genome duplication in Kluyveromyces polysporus and Saccharomyces cerevisiae. Devin R. Scannell, A. Carolin Frank, Kevin P. Byrne, Gavin C. Conant, Kenneth H. Wolfe. Smurfit Institute, Dept. of Genetics, Trinity College Dublin, D2, Ireland.
   We have determined a draft sequence (7.8x coverage) of the genome of the yeast species Kluyveromyces polysporus. This species is descended from the same whole-genome duplication (WGD) event as S. cerevisiae but it appears to have separated from the S. cerevisiae lineage almost immediately after the WGD happened. Similar types of genes were retained in duplicate in the two genomes, with preferential retention of signal transduction and glucose metabolism genes, which confirms the role of natural selection in this process. We note however that while more protein kinases have been retained in duplicate than expected by chance in both species, the specific kinases often differ. For instance, the PRK1/ARK1 pair has been retained in duplicate in both species, but BUB1/MAD3 has been retained in duplicate by S. cerevisiae only and SNF1 has been retained in duplicate by K. polysporus only. Consistent with this, at loci where K. polysporus and S. cerevisiae each retained only one gene copy they show almost random choice of which copy to retain. Thus, the K. polysporus genome contains pairs of duplicated chromosomal regions that are superficially similar to those in S. cerevisiae, but whose gene composition is very different. Almost half of the genes that are single-copy in both species are paralogs, not orthologs.

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