Large genome deletions reveal gene effects on ethanol tolerance in Saccharomyces cerevisiae

The yeast Saccharomyces cerevisiae, which is a model system for biological research, has been widely used as an industrial host. Using the mazF-mediated deletion system, we made large deletions, including both terminal and internal regions of the chromosome. We obtained 12 deletion strains with different sizes of the deleted genome region(s), varying from 20 kb to 80 kb. Each deletion removed a cluster of nonessential genes, as deduced by an online prediction program. Phenotype analysis of the mutants with large deletions showed that genome regions YOR124C/YOR134W and YOL020W/YOL011W appeared to be related to ethanol tolerance and high salinity sensitivity, respectively. The loss of CAT5, ADE2, or RGA1 reduced the ethanol tolerance of yeast. Dispensable genes or interactions among non-essential genes were involved in the functional effects of genome deletions.