FIGURE 1: Intracellular proline regulates the yeast replicative lifespan. (A and D) Lifespan of yeast cells with increased or decreased proline levels. The data for the wild-type strain (WT; BY4741) was the same as Figure 1A and 1D. The results of other mutants, which were analyzed independently, and WT were combined. (B, C, E and F) Intracellular proline levels in the indicated strains at log and stationary phases compared with that in WT at log phase. The values are the means and standard deviation of results from three independent experiments. *, p < 0.05; **, p < 0.01, versus WT calculated with the Dunnett's test.