Unveiling genetic anchors in Saccharomyces cerevisiae: QTL mapping identifies IRA2 as a key player in ethanol tolerance and beyond

Abstract

Ethanol stress inSaccharomyces cerevisiaeis a well-studied phenomenon, but pinpointing specific genes or polymorphisms governing ethanol tolerance remains a subject of ongoing debate. Naturally found in sugar-rich environments, this yeast has evolved to withstand high ethanol concentrations, primarily produced during fermentation in the presence of suitable oxygen or sugar levels. Originally a defense mechanism against competing microorganisms, yeast-produced ethanol is now a cornerstone of brewing and bioethanol industries, where customized yeasts require high ethanol resistance for economic viability. However, yeast strains exhibit varying degrees of ethanol tolerance, ranging from 8% to 20%, making the genetic architecture of this trait complex and challenging to decipher. In this study, we introduce a novel QTL mapping pipeline to investigate the genetic markers underlying ethanol tolerance in an industrial bioethanolS. cerevisiaestrain. By calculating missense mutation frequency in a prominent QTL region within a population of 1011S. cerevisiaestrains, we uncovered rare occurrences in geneIRA2. Following molecular validation, we confirmed the significant contribution of this gene to ethanol tolerance, particularly in concentrations exceeding 12% of ethanol.IRA2pivotal role in stress tolerance due to its participation in the Ras-cAMP pathway was further supported by its involvement in other tolerance responses, including thermotolerance, low pH tolerance, and resistance to acetic acid. Understanding the genetic basis of ethanol stress inS. cerevisiaeholds promise for developing robust yeast strains tailored for industrial applications.