Genome evolution: Lessons from Genolevures

Abstract

In the past years, yeast genome-sequencing programs have been widely developed. Two of them, namely Genolevures I and II, were devoted to the exploration of hemiascomycetous yeasts. The first one covered 13 species with partial random sequencing (0.2-0.4X coverage). The second one led to the complete genome sequence (8-11X coverage) of four species. The overall evolution of genome structures and the phylogeny could already be deduced from the partial sequencing data, while their mechanisms needed the analysis of complete genome. The main results that came out of these projects are that evolution superimposes stochastic discrete events to the continuous mutation flow. Concerning functional aspects, examination of partial sequences revealed only general trends. Here, we performed a detailed analysis of the genes involved in central metabolism and in the anaerobiosis/aerobiosis pathways on the complete genome of three representative yeasts, Saccharomyces cerevisiae, Kluyveromyces lactis, and Yarrowia lipolytica. This comparison revealed subtle and relevant differences in gene content, which explain in a satisfactory way the known physiological specificities of these three species. This analysis outlines the need for high quality and complete genome sequence when comparing biological processes and functions.