Figure 1.

Pak1 is required for fusion during mating. (A) Fusion assay of bilateral ste20 and pak1 crosses. Top, media used to select prototrophic fusion products from ste20α x ste20a (top left) and α pak1 x a pak1 (top right) crosses. Bottom, wild-type control crosses corresponding to the marker matched bilateral ste20 cross (bottom left) and the bilateral pak1 cross (bottom right). (B) MFα pheromone gene expression in wild-type α strain and α cpk1, α pak1, and ste20α strains alone, α and α cpk1 strains cocultured with wild-type a, α pak1 cocultured with a pak1, and ste20α cocultured with ste20a. Cells were incubated on V8 medium for 24 h at room temperature, RNA was prepared, and MFα gene expression was assessed by Northern blot analysis with an MFα1 gene probe. C. neoformans ACT1 was used as a loading control.