FIG. 3.

The SPI1 gene is required for S. cerevisiae adaptation and growth under 2,4-D stress as indicated by a comparison of susceptibilities by spot assays or growth curves (A) and cell viabilities (B) of wild-type (WT; •, ▪) and Δspi1 (○, □) strains in the absence (•, ○) or presence (▪, □) of 2,4-D (0.45 mM; pH 3.5). Values are representative of the many growth experiments carried out. Cell suspensions used to prepare the spots or to inoculate the liquid media were cultivated in the absence of herbicide until a standardized OD₆₀₀ of 0.5 ± 0.05 was attained, in mid-exponential phase. The cell suspensions used to prepare the spots in lanes B were 1/4 dilutions of the cell suspensions (OD₆₀₀ = 0.05 ± 0.005) in lanes A.