Disruption of aldo-keto reductase genes leads to elevated markers of oxidative stress and inositol auxotrophy in Saccharomyces cerevisiae.

A large family of aldo-keto reductases with similar kinetic and structural properties but unknown physiological roles is expressed in the yeast Saccharomyces cerevisiae. Strains with one or two AKR genes disrupted have apparently normal phenotypes, but disruption of at least three AKR genes results in a heat shock phenotype and slow growth in inositol-deficient culture medium (Ino(-)). The present study was carried out to identify metabolic or signaling defects that may underlie phenotypes that emerge in AKR deficient strains. Here we demonstrate that pretreatment of a pentuple AKR null mutant with the anti-oxidative agent N-acetyl-cysteine rescues the heat shock phenotype. This indicates that AKR gene disruption may be associated with defects in oxidative stress response. We observed additional markers of oxidative stress in AKR-deficient strains, including reduced glutathione levels, constitutive nuclear localization of the oxidation-sensitive transcription factor Yap1 and upregulation of a set of Yap1 target genes whose function as a group is primarily involved in response to oxidative stress and redox balance. Genetic analysis of the Ino(-) phenotype of the null mutants showed that defects in transcriptional regulation of the INO1, which encodes for inositol-1-phosphate synthase, can be rescued through ectopic expression of a functional INO1. Taken together, these results suggest potential roles for AKRs in oxidative defense and transcriptional regulation.