Figure 8.

Ste20 and Pak1 are not interchangeable. (A) ste20α ura5 and α pak1 ura5 strains were transformed with plasmids expressing either STE20α or PAK1. Each strain also was transformed with a control plasmid. ste20 (left) and pak1 (right) bilateral crosses were prepared with each transformant and analyzed for filament production. Representative crosses were photographed at 100 and 400× (insets) magnification to visualize filamentation and basidiospore production. (B) ste20α transformants were assessed for growth at 37°C. Cells were grown overnight at 30 and 37°C and photographed at 1000× magnification with DIC optics. At 37°C ste20α mutants bearing vector alone or the PAK1 plasmid exhibited a cytokinesis defect, resulting in long chains of connected and elongated cells. Introduction of the STE20α gene complemented the cytokinesis defect, resulting in a wild-type budding yeast cell morphology.