Analysis of the essentiality of ROM2 genes in the pathogenic yeasts Candida glabrata and Candida albicans using temperature-sensitive mutants.

To analyse the essentiality of the ROM2 genes originating from the pathogenic yeasts Candida glabrata and Candida albicans by using temperature-sensitive (ts) mutants. Based on the general concepts that ts mutations are generated by virtue of point mutation within essential genes, we have previously established a novel method (termed 'ETS system' for screening and identification of essential genes using ts mutants of C. glabrata). According to this ETS system, the present study successfully identified a putative C. glabrata ROM2 homologue as an essential gene that complements its point mutation (Cys-1275/Tyr substitution). The C. albicans ROM2 mutant (Cys-1281/Tyr), constructed patterned after this point mutation, also displayed ts phenotype. Both ts mutants recovered colony-forming ability, with concomitant suppression of lysis phenotype, at the elevated temperature in the presence of 1 mol l(-1) sorbitol as an osmotic stabilizer. Sequence alignment revealed that human genome possesses relatively low homology against Rom2 homologues, which are highly conserved among yeast species. ROM2 genes of C. glabrata and C. albicans are essential for viability, probably involved in cell wall integrity. ROM2 genes essential for both Candida species may be a potentially useful antifungal targets from chemotherapeutic viewpoint.