Tracking alternative versions of the galactose gene network in the genus Saccharomyces and their expansion after domestication
A. Pontes et al. "Tracking alternative versions of the galactose gene network in the genus Saccharomyces and their expansion after domestication" iScience 27:108987 (2024) [DOI:10.1016/j.isci.2024.108987]
When Saccharomyces cerevisiae grows on mixtures of glucose and galactose, galactose utilization is repressed by glucose, and induction of the GAL gene network only occurs when glucose is exhausted. Contrary to reference GAL alleles, alternative alleles support faster growth on galactose, thus enabling distinct galactose utilization strategies maintained by balancing selection. Here, we report on new wild populations of Saccharomyces cerevisiae harboring alternative GAL versions and, for the first time, of Saccharomyces paradoxus alternative alleles. We also show that the non-functional GAL version found earlier in Saccharomyces kudriavzevii is phylogenetically related to the alternative versions, which constitutes a case of trans-specific maintenance of highly divergent alleles. Strains harboring the different GAL network variants show different levels of alleviation of glucose repression and growth proficiency on galactose. We propose that domestication involved specialization toward thriving in milk from a generalist ancestor partially adapted to galactose consumption in the plant niche.
Whole-genome data has been deposited in DDBJ/ENA/GenBank and is publicly available as of the date of publication. Accession numbers are listed in the key resources table. The sequences of the GAL/PGM genes of the strains isolated in Taiwan have been deposited in GenBank and are publicly available as of the date of publication. Accession numbers are listed in the key resources table. This paper does not report original code.