High Resolution QTL Mapping of Ethanol Tolerance in Saccharomyces cerevisiae Using Advanced Intercross Lines and Selective DNA Pooling

Roni Haas ronime@tx.technion.ac.il ¹ Guy Horev ² Ehud Lipkin ³ Inbar Kesten ¹ Keren Buhnik-Rosenblau ¹ Morris Soller ³ Yechezkel Kashi ¹

¹Faculty of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Haifa, Israel
²Bioinformatics Knowledge Unit, Technion-Israel Institute of Technology, Haifa, Israel
³Department of Genetics, The Hebrew University of Jerusalem, Jerusalem, Israel

Ethanol, the end product of fermentation in Saccharomyces cerevisiae, is the main biofuel used worldwide. Since ethanol is toxic to the yeast cell, ethanol production is inhibited by its accumulation. Therefore, understanding the genetic basis of ethanol tolerance is important for the development of improved yeast strains with higher ethanol tolerance and yields. However, up to now, genomic elements affecting ethanol tolerance have only been mapped at low resolution, hindering their identification.

Here, we used Advanced Intercrossed Line (AIL) design, to perform high resolution mapping of QTLs affecting ethanol tolerance in yeast.

Selective DNA Pooling (SDP) and whole-genome sequencing were used in F6 of a cross between two widely separated S. cerevisiae haploid strains. Fifty and 95 QTLs affecting growth and survival, respectively, were identified by applying uniquely developed statistical methods.

The median size of a QTL Region (QTLR) was 12.1 Kb (growth) and 10.5 Kb (survival). These QTLRs are much narrower than previous reports. Importantly, some QTLRs included only a single gene. The mapping revealed significantly enriched biological processes important for ethanol tolerance in S. cerevisiae.