Originally published as Genetics Published Articles Ahead of Print on December 28, 2006.

Genetics, Vol. 175, 1479-1487, March 2007, Copyright © 2007
doi:10.1534/genetics.106.065292

Genetic Dissection of Ethanol Tolerance in the Budding Yeast Saccharomyces cerevisiae

X. H. Hu*,1, M. H. Wang*,1, T. Tan*, J. R. Li*, H. Yang*, L. Leach{dagger}, R. M. Zhang* and Z. W. Luo*,{dagger},2

* Laboratory of Population and Quantitative Genetics, Department of Biostatistics, State Key Laboratory of Genetic Engineering, Institute of Biomedical Sciences, School of Life Sciences, Fudan University, Shanghai 200433, China and {dagger} School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom

2 Corresponding author: Laboratory of Population and Quantitative Genetics, Institute of Genetics, Fudan University, 220 Handan Rd., Shanghai 200433, China.
E-mail: z.luo{at}bham.ac.uk

Uncovering genetic control of variation in ethanol tolerance in natural populations of yeast Saccharomyces cerevisiae is essential for understanding the evolution of fermentation, the dominant lifestyle of the species, and for improving efficiency of selection for strains with high ethanol tolerance, a character of great economic value for the brewing and biofuel industries. To date, as many as 251 genes have been predicted to be involved in influencing this character. Candidacy of these genes was determined from a tested phenotypic effect following gene knockout, from an induced change in gene function under an ethanol stress condition, or by mutagenesis. This article represents the first genomics approach for dissecting genetic variation in ethanol tolerance between two yeast strains with a highly divergent trait phenotype. We developed a simple but reliable experimental protocol for scoring the phenotype and a set of STR/SNP markers evenly covering the whole genome. We created a mapping population comprising 319 segregants from crossing the parental strains. On the basis of the data sets, we find that the tolerance trait has a high heritability and that additive genetic variance dominates genetic variation of the trait. Segregation at five QTL detected has explained ~50% of phenotypic variation; in particular, the major QTL mapped on yeast chromosome 9 has accounted for a quarter of the phenotypic variation. We integrated the QTL analysis with the predicted candidacy of ethanol resistance genes and found that only a few of these candidates fall in the QTL regions.