Figure 1.

Differential sensitivity of yeast strains to the cytotoxic effect of PR-5 proteins. (Upper) Cells of strains GRF167 (○, □) and BWG7a (▪, •) were incubated in YPD medium with (□, ▪) and without (○, •) 50 μg/ml of purified tobacco osmotin for the time lengths indicated. Subsequently, cells were diluted and plated, and the number of viable counts was determined after incubation at 30°C for 2 days. (Lower) Approximately 10⁷ cells per ml of walled cells (□, ▪) and spheroplasts (○, •) of strain BWG7a were incubated at 30°C for 1 hr in YPD or 0.8 M sorbitol, respectively, containing the indicated concentrations of tobacco osmotin (▪, •) and the osmotin-like protein A9 (○, □) purified from cultured cell suspensions of A. nummularia. Viable counts were determined as indicated above and are shown normalized to the value without added proteins.