Research Paper Volume 10, Issue 9 pp 2407—2427

Figure 1. Mild transient heat shock leads to replicative lifespan extension triggered by enhanced respiratory activity. (A) Mean and maximum replicative lifespan (RLS) is extended in yeast that undergo a 3-hour heat shock at 34^oC early in their life (1-3 generations). Control cells were kept constantly at 30^oC. The number of curated cells is 81 for WT and 73 for WT HS. Significance of the results was tested with log-rank (Mantel–Cox) test. P value is <0.0001. (B) Differential gene expression measured by RNA sequencing (RNA-Seq) reveals changes in cellular metabolic activity, most prominently repression of glycolysis and activation of respiration. Heat map displays RNA-Seq-derived differential expression (contrasted to control) of selected genes, grouped according to their respective metabolic pathways. Gray X signs indicate statistically insignificant fold changes. Gene names are indicated on the left of each heat map. (C) qPCR measurement of differential gene expression confirms repression of glycolysis and activation of respiration, as well as reveals activation of the pentose phosphate pathway and glutathione recycling. Color of the squares on the heat map corresponds to the mean value of the log fold change from three biological and three technical replicates. UBC6 was used for normalization. (D) Oxygen consumption is increased at heat shock in WT yeast, but remains unchanged in the respiration deficient petite strain and in HAP4Δ strains. Oxygen uptake was measured polarographically using an oxygraph equipped with a Clark-type electrode. Data on the graph are mean ± SEM from three biological and three technical replicates. P values were calculated using ANOVA plus post hoc. ***P < 0.001; **P < 0.01; *P < 0.05. (E) Mean and maximum replicative lifespan (RLS) remain unchanged in petite strain under heat shock. Control cells were kept constantly at 30^oC. The number of curated cells is 80 for petite and 89 for petite HS. P value is >0.05 (Mantel-Cox). (F) Mean and maximum replicative lifespan (RLS) remain unchanged in HAP4Δ strain under heat shock. Control cells were kept constantly at 30^oC. The number of curated cells is 76 for HAP4Δ and 92 for HAP4Δ HS. P value is >0.05 (Mantel-Cox).