A mitochondrial superoxide dismutase (SOD2) is the first line of antioxidant defense against mitochondrial superoxide. Even though the involvement of SOD2 in lifespan has been studied extensively in several organisms, characterization of the aging process has not been performed for the sod2 mutant (sod2?) of a prominent model Schizosaccharomyces pombe. In this study, we measured the chronological lifespan of sod2? cells by their ability to survive in long-term culture. SOD2 deficiency drastically decreased cell viability in the stationary phase. The mutation frequency of nuclear DNA in sod2? was elevated in the stationary phase, and cellular proteins and nuclear DNA were extensively degraded, concurrent with cell death. The sod2 gene in wild-type cells could be induced by an increase in endogenous oxidative stresses, after which SOD2 activity was substantially elevated during the stationary phase. Culture in a lower glucose concentration (calorie restriction) prominently extended the sod2? lifespan. Therefore, S. pombe SOD2 plays a critical role in longevity through its upregulation in the non-dividing phase.
