Comparative genomics between S. cerevisiae and S. kudriavzevii.

Yeasts belonging to the genus Saccharomyces play an important role in human-driven fermentations. The species S. cerevisiae hasbeen widely studied because it is the dominant yeast in most fermentations and it has been widely used as a model eukaryoticorganism. Recently, other species of the Saccharomyces genus are gaining interest to solve the new challenges that thefermentation industry are facing. One of these species is S. kudriavzevii, which exhibits interesting physiological propertiescompared to S. cerevisiae, such as a better adaptation to grow at low temperatures, a higher glycerol synthesis and lowerethanol production. The aim of this study is to understand the molecular basis behind these phenotypic differences ofbiotechnological interest by using a species-based comparative genomics approach.In this work, we sequenced, assembled and annotated two new genomes of S. kudriavzevii.We used a combination of differentstatistical methods to identify functional divergence, signatures of positive selection and acceleration of substitution rates atspecific amino acid sites of proteins in S. kudriavzevii when compared to S. cerevisiae, and vice versa.Our results showed that most functionally divergent proteins between these two species are involved in cellular response toosmotic and oxidative stress, proteins belonging to sphingolipid metabolic pathway, and riboflavin biosynthesis. Genes of theriboflavin biosynthesis are also among those genes with a significant higher rate of nucleotide substitution. Finally, we provide alist of candidate genes in which positive selection could be acting during the evolution of the S. kudriavzevii clade. Three of thosecandidates (FBA1, ZIP1 and RQC2) showed accelerated evolutionary rates as well.