A Candida albicans RAS-related gene (CaRSRl) is involved in budding, cell morphogenesis and hypha development

Abstract

Summary: Candida albicans, the most important human fungal pathogen, is a dimorphic fungus that can grow either as a yeast or as a hyphal form in response to medium conditions. A RAS-related C. albicans gene (CaRSRl) was isolated as a suppressor of a cdc24b bud-emergence mutation of the baker's yeast, Saccharomyces cerevisiae. The deduced protein encoded by CaRSRl is 248 amino acids long and 56% identical to that encoded by the 5. cerevisiae RSRl (BUDI) gene. Disruption of CaRSRl in C. albicans indicated that CaRSRl is involved in both yeast and hypha development. In the yeast phase, CaRSRl is required for normal (polar) bud site selection and is involved in cell morphogenesis; in the yeast-mycelial transition it is involved in germ tube emergence; and in the development of the hyphae it is involved in cell elongation. The disruption of CaRSRl leads to reduced virulence in both heterozygote and homozygote disruptants in a dose-dependent manner. The reduced virulence can be attributed to the reduced germination and shorter hyphae resulting from the disruption of CaRSRl.