Genetic Basis of Variation in Heat and Ethanol Tolerance in Saccharomyces cerevisiae

Saccharomyces cerevisiae has the capability of fermenting sugar to produce concentrations of ethanol that are toxic to most organisms. Other Saccharomyces species also have a strong fermentative capacity, but some are specialized to low temperatures, whereas S. cerevisiae is the most thermotolerant. Although S. cerevisiae has been extensively used to study the genetic basis of ethanol tolerance, much less is known about temperature dependent ethanol tolerance. In this study, we examined the genetic basis of ethanol tolerance at high temperature among strains of S. cerevisiae. We identified two amino acid polymorphisms in SEC24 that cause strong sensitivity to ethanol at high temperature and more limited sensitivity to temperature in the absence of ethanol. We also identified a single amino acid polymorphism in PSD1 that causes sensitivity to high temperature in a strain dependent fashion. The genes we identified provide further insight into genetic variation in ethanol and temperature tolerance and the interdependent nature of these two traits in S. cerevisiae.