Functional analysis of Candida albicans genes encoding SH3-domain-containing proteins.

Postgenomic gene-function analyses with Candida albicans are hindered by its constitutive diploidy and the lack of a sexual cycle. Rapid generation of mutant strains can be achieved using PCR-based techniques for directed gene alterations. Here, we report the analyses of nine C. albicans genes that encode Src Homology 3-domain proteins. Phenotypic analyses included the potential of the mutants to form hyphal filaments, maintain a polarized actin cytoskeleton or the ability to generate large vacuoles in the germ cells and in subapical compartments. The C. albicans homologs of the Saccharomyces cerevisiae BBC1, BOI2, BUD14, FUS1, HSE1, PIN3, RVS167, RVS167-2 and SHO1 were all found to be nonessential. Deletion of RVS167 resulted in a strain with a decreased ability to form hyphal filaments. The number of cortical actin patches was increased in Deltarvs167 strains and their distribution was depolarized in both mother and daughter yeast cells and along the hyphae during filamentous growth stages. Polarization of patches could be restored upon reintroduction of the wild-type gene. Deletion of BOI2 was found to generate a defect in vacuolar fusion in hyphae. In contrast to a deletion in the Deltawal1 gene, Deltaboi2 cells formed abundant hyphae, indicating that fragmented vacuoles do not inhibit filamentation. Placing BOI2 under control of the MAL2-promoter allowed the regulation of this phenotype depending on the growth conditions.