FIGURE 11.

α-Tocopherol acts upstream of Tsa1 and Yap1 and has no protective effect toward H₂O₂. A, deletion mutants for Yap1 and Tsa1 were compared with their isogenic wild type strain (BY4741). Cells were grown to mid-log phase and serial diluted onto rich medium + 0.2% ethanol (control) or rich medium containing edelfosine (20 μg/ml), α-tocopherol (50 μm), or both combined. Plates were incubated for 3 days at 25 °C. B, strains lacking Tsa1 and Yap1 were grown to mid-log phase and then treated with the indicated concentrations of edelfosine and H₂O₂ in rich medium. 25 and 100 μm α-tocopherol is shown in combination with edelfosine (10 μg/ml) and H₂O₂ (1 mm), respectively. Similar curves were obtained for the isogenic wild type BY4741 (not shown) in all conditions. Results are presented as the mean ± S.D. of a representative experiment performed at least three times.