MFα1 , the Gene Encoding the α Mating Pheromone of Candida albicans

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Abstract
Candida albicans , the single most frequently isolated human fungal pathogen, was thought to be asexual until the recent discovery of the mating-type-like locus ( MTL ). Homozygous MTL strains were constructed and shown to mate. Furthermore, it has been demonstrated that opaque-phase cells are more efficient in mating than white-phase cells. The similarity of the genes involved in the mating pathway in Saccharomyces cerevisiae and C. albicans includes at least one gene ( KEX2 ) that is involved in the processing of the α mating pheromone in the two yeasts. Taking into account this similarity, we searched the C. albicans genome for sequences that would encode the α pheromone gene. Here we report the isolation and characterization of the gene MFα1 , which codes for the precursor of the α mating pheromone in C. albicans . Two active α-peptides, 13 and 14 amino acids long, would be generated after the precursor molecule is processed in C. albicans . To examine the role of this gene in mating, we constructed an mfα1 null mutant of C. albicans . The mfα1 null mutant fails to mate as MTLα , while MTL a mfα1 cells are still mating competent. Experiments performed with the synthetic α-peptides show that they are capable of inducing growth arrest, as demonstrated by halo tests, and also induce shmooing in MTL a cells of C. albicans . These peptides are also able to complement the mating defect of an MTLα kex2 mutant strain when added exogenously, thereby confirming their roles as α mating pheromones.