FIGURE 1.

Loss of Oma1 affects cellular tolerance to mitochondrial stress stimuli. A, survival of WT and oma1Δ cells. Synchronized cultures were grown to mid-log phase and acutely treated with 1 mm H₂O₂ or chronically exposed to 45 μm CCCP. Samples were diluted to 300 cells and plated for survival onto glucose (YPD) plates, and the number of colony forming units was assessed after 2 days of incubation at 28 °C. The error bars indicate S.D. (n = 5); *, p < 0.05; **, p < 0.005 (unpaired t test, one-way analysis of variance). B, WT, oma1Δ, sod2Δ, and oma1Δ sod2Δ strains were grown to stationary phase in complete medium containing 2% glucose. Cells were serially diluted and spotted onto plates containing 2% glucose (YPD), galactose (YPGal), or glycerol/lactate (YPGL) as a sole carbon source. Pictures were taken after 2 (glucose plates) or 4 (galactose or glycerol/lactate plates) days of incubation at 28 °C. Gly., glycerol; Lac., lactate. C, aconitase activity in mitochondria isolated from the respective strains grown to logarithmic or stationary phase (mean values ± S.D., n = 3 biological replicates). The bottom panel shows actual data and p values for respective stationary phase cultures. *, WT versus indicated mutants; #, sod2Δ versus sod2Δ oma1Δ cells; unpaired t test, one-way analysis of variance. D, steady-state levels of aconitase (Aco1) and porin (loading control) in the strains described above. The TCA-precipitated whole cell extracts were subjected to SDS-PAGE and analyzed by immunoblotting with the respective antibodies. E, top panel, visualization of Htt-103Q-GFP in WT and oma1Δ cells. Synchronized cells bearing an empty YIp vector or an integrative plasmid with GAL1 promoter-driven Htt-103Q-GFP were pregrown in YPGL + 0.2% glucose. The cultures were then transferred into galactose-containing medium and incubated for 6 h at 28 °C to induce Htt-103Q-GFP expression and assessed by confocal microscopy. The scale bars indicate 5 μm. Bottom panel, immunoblot analysis of Htt-103Q-GFP levels in WT and oma1Δ cells. DIC, differential interference contrast.