Figure 2.

Activated STE5 alleles cause G₁ arrest and induce morphological changes. (A) A ste4Δ ste5Δ strain carrying an empty vector or the same vector expressing either wild-type Ste5-GST or the indicated activated mutant derivatives (as GST fusions), under the control of the GAL1 promoter were pregrown in SCRaf to an A_{600 nm} = 0.2, and then galactose (2% final concentration) was added to induce expression of the proteins. At the indicated times, triplicate samples of the cultures were removed and cell number was determined as described in MATERIALS AND METHODS; values plotted represent the average (SD was <10%). (B) Samples of the cultures shown in A were removed 6 h after addition of galactose, fixed for 30 min in 5% formaldehyde at room temperature, washed in PBS, stained for 30 min at room temperature with Calcofluor, spotted on glass slides, mounted with a coverslip, and examined under the fluorescence microscope, as described in MATERIALS AND METHODS.