Population genomics of Saccharomyces eubayanus and the origin of lager-brewing yeast

HITTINGER, C; BONTRAGER, M; GONCALVES, P; SAMPAIO, JP; LIBKIND, DIEGO

Princenton

Encuentro; Yeast Genetics & Molecular Biology Meeting; 2012

The lager-brewing yeast Saccharomyces pastorianus has been long known to be an allopolyploid hybrid of S. cerevisiae and a cold-adapted species belonging to the S. bayanus species complex. Recently, we discovered the missing contributor of lager yeast in Patagonia and described this species as S. eubaynaus. Comparisons of the genome sequence of S. eubayanus to the lager yeast genome sequence of revealed that the non-S. cerevisiae portion of its genome was 99.56 % identical and helped identify domestication genes involved in sugar and sulfur metabolism. S. eubayanus was also found to be genetically distinct from the other non-hybrid species of the S. bayanus species complex, S. uvarum, with 6.89% divergence and strong post-zygotic isolation. We have isolated over 200 additional strains of S. eubayanus and S. uvarum in Argentina along a longitudinal transect from Tierra del Fuego northwards for over 1,500 km. Preliminary analysis of dozens of genome sequences of S. eubayanus and S. uvarum show that both species are genetically more diverse than S. cerevisiae. Highly divergent strains of each species can even be found within the same national park, suggesting they may have unusually large effective populations sizes and/or considerable cryptic niche-partitioning. Comparisons to lager-brewing strains will help identify the genetic targets of domestication and determine how standing natural variation affected the evolution of lager yeast.