FIGURE 4.

Knock-out PTC7 mutant presents impaired antioxidant defenses. A, analysis of PTC7 gene expression. Quantitative analysis of PTC7 expression was performed using quantitative RT-PCR in wild-type yeast. Data are expressed as relative expression compared with 2% (w/v) YPD or untreated yeast. a, p < 0.01 significant differences. Error bars represent S.D. Cd²⁺, cadmium sulfate; TBP, tert-butyl peroxide; LNA, linolenic acid. n = 3 in all experiments. B, cell viability was monitored under induced oxidative stress. Yeast were grown in YPD or YPG. After 5 days, cells were spotted by serial dilutions (1:10) from A_{660 nm} = 0.5 onto YPD plates containing the indicated concentrations of oxidative stress agents. Plates were incubated at 30 °C for 3 days and imaged. C, quantification of protein carbonylation. Yeast were grown for 7 days to monitor the evolution of protein carbonylation content. Fresh yeast extracts (50 μg) were harvested at marked times (days) and analyzed. Carbonylation content is normalized (relative units) to wild-type levels at day 1. Error bars represent S.D. a, p < 0.05 compared with WT. n = 3 in all experiments. a.u., arbitrary units.