Glutathione, but not transcription factor Yap1, is required for carbon source-dependent resistance to oxidative stress in Saccharomyces cerevisiae

Resistance of haploid yeast to hydrogen peroxide and to tert-butylhydropero xide strongly increases when 4% glucose is replaced by glycerol or ethanol as the carbon source of the complex medium. Using a GSH1-promoter-lacZ-fusi on reporter construct we could demonstrate that GSH1 is one of the genes th at are up-regulated during the shift from fermentative to oxidative metabol ism. A gsh1 mutant did not exhibit respiratory growth resistance to H2O2, w hereas it was only slightly impaired in acquiring resistance against t-BOOH in the same experimental conditions. An isogenic Delta yap1 mutant, althou gh more sensitive to oxidative stress than the wild-type (WT), could increa se resistance to both peroxides by a similar factor as observed for the WT when shifted from 4% glucose to a non-fermentable carbon source. This indic ates that in this case induction of resistance to oxidative stress is indep endent from Yap1 and from the Yap1-mediated stress response via the STRE mo tif.