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

Superoxide dismutases, both cytosolic Cu,Zn-SOD encoded by SOD1 and mitochondrial Mn-SOD encoded by SOD2, serve Saccharomyces cerevisiae cells for defense against the superoxide radical but the phenotypes of sod1 Delta and sod2 Delta mutant strains are different. Compared with the parent strain and the sod1 Delta mutant, the sod2 Delta 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 degrees C, the sod2 Delta showing the highest sensitivity, especially when cultured in air. Addition of 1 mmol/L glutathione to the medium restores aerobic growth of the sod1 Delta mutant but has only a minor effect on the growth of the sod2 Delta strain at 37 degrees C. The sod2 Delta strain is also sensitive to As-III and As-V 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 protecting S. cerevisiae cells against other stresses - high osmolarity, heat and metalloid stress.