Fig. 7. Overexpression of Cdc42 or the PAK homolog Cla4 rescues the osmosensitive phenotype caused by a ste20Δ mutation. Strain DR76 (ssk2Δ ssk22Δ ste20Δ) was transformed with the galactose promoter containing pYES2 (Vector), wild-type CDC42 inserted into pYES2 (Cdc42) or a high copy-number plasmid, pCC1079 (Chen et al., 1997) containing the wild-type CLA4 gene under its own promoter (Cla4). Transformants were streaked onto YPGal or on YPGal containing 1.5 M sorbitol and incubated at 30°C.