We show that the dominant activated allele of the yeast RAS gene, RAS2 ala18,val19, led to redox imbalance in exponential-phase cells and to excretion of almost all of the cellular glutathione into the medium when the cells reached early-stationary phase. The mitochondria of the mutant stained strongly with dihydrorhodamine 123 (DHR) and the cells displayed a very short mother cell-specific lifespan. Adding 1 mM reduced glutathione (GSH) to the medium partly restored the lifespan. The corresponding RAS2 + rho-zero strain also displayed a short lifespan, excreted nearly all of its GSH, and stained positively with DHR. Adding 1 mM GSH completely restored the lifespan of the RAS2 + rho-zero strain to that of the wild-type cells. The double mutant RAS2 ala18,val19 rho-zero cells showed the same lifespan as the RAS2 ala18,val19 cells, and the effect of glutathione in restoring the lifespan was the same, indicating that both mutations shorten lifespan through a similar mechanism. In the RAS2 ala18,val19 mutant strain and its rho-zero derivative we observed for the first time a strong electron spin resonance (ESR) signal characteristic of the superoxide radical anion. The mutant cells were, therefore, producing superoxide in the absence of a complete mitochondrial electron transport chain, pointing to the existence of a possible non-mitochondrial source for ROS generation. Our results indicate that oxidative stress resulting from a disturbance of redox balance can play a major role in mother cell-specific lifespan determination of yeast cells. © 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.
Heeren, G., Jarolim, S., Laun, P., Rinnerthaler, M., Stolze, K., Perrone, G. G., … Breitenbach, M. (2004). The role of respiration, reactive oxygen species and oxidative stress in mother cell-specific ageing of yeast strains defective in the RAS signalling pathway. FEMS Yeast Research, 5(2), 157–167. https://doi.org/10.1016/j.femsyr.2004.05.008