Protective role of mitochondrial superoxide dismutase against high osmolarity, heat and metalloid stress inSaccharomyces cerevisiae

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Abstract
Superoxide dismutases, both cytosolic Cu,Zn-SOD encoded bySOD1 and mitochondrial Mn-SOD encoded bySOD2, serveSaccharomyces cerevisiae cells for defense against the superoxide radical but the phenotypes ofsod1Δ andsod2Δ mutant strains are different. Compared with the parent strain and thesod1Δ mutant, thesod2Δ mutant shows a much more severe growth defect at elevated salt concentrations, which is partially rescued by 2 mmol/L glutathione. The growth of all three strains is reduced at 37 °C, thesod2Δ showing the highest sensitivity, especially when cultured in air. Addition of 1 mmol/L glutathione to the medium restores aerobic growth of thesod1Δ mutant but has only a minor effect on the growth of thesod2Δ strain at 37 °C. Thesod2Δ strain is also sensitive to AsIII and AsV and its sensitivity is much more pronounced under aerobic conditions. These results suggest that, unlike the Sod1p protein, whose major role is oxidative stress defense, Sod2p also plays a role in protectingS. cerevisiae cells against other stresses — high osmolarity, heat and metalloid stress.