Figure 2.

Heat-induced death of cit1 null cells is mediated by ROS. (A) Observation of ROS accumulation in the cells exposed to heat stress. Yeast strains (wild type, Δcit1, Δcit2, and Δcit1Δcit2) grown in SCD were incubated at 30 or 50°C for 10 min. The cells were then stained with DCFH-DA and examined by fluorescence microscopy. Bar, 10 μm. (B) Percentage of ROS-accumulating cells after exposure to heat stress. DCFH-DA–positive cells were counted in fluorescence images and total cells in corresponding differential interference contrast (DIC) images. (C) Effect of Tiron on the temperature-dependent survival rate of yeast cells. Cells of the strains listed above were incubated at 50°C for 30 min with or without the addition of 10 mM Tiron, and aliquots of the sample were then taken. Surviving cells were evaluated by CFU assays carried out in triplicate.