SST2, a Regulator of G-Protein Signaling for theCandida albicansMating Response Pathway

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Abstract
Candida albicanscontains a functional mating response pathway that is similar to the well-studied system ofSaccharomyces cerevisiae. We have characterized aregulator ofGproteinsignaling (RGS) homolog inC. albicanswith sequence similarity to theSST2gene ofSaccharomyces cerevisiae. Disruption of this gene, which had been designatedSST2, causes an opaqueMTLa/MTLaderivative of strain SC5314 to show hypersensitivity to theC. albicansα-factor. This hypersensitivity generates an enhanced cell cycle arrest detected in halo assays but reduces the overall mating efficiency of the cells. Transcriptional profiling of the pheromone-regulated gene expression in thesst2mutant shows a pattern of gene induction similar to that observed in wild-type cells, but the responsiveness is heightened. This involvement of an RGS in the sensitivity to pheromone is consistent with the prediction that the mating response pathway inC. albicansrequires the activation of a heterotrimeric G protein.