Candida albicans MTLa2 regulates the mating response through both the a-factor and α-factor sensing pathways

The diploid fungal pathogen Candida albicans has three configurations at the mating type locus (MTL): heterozygous (a/alpha) and homozygous (a/a or alpha/alpha). C. albicans MTL locus encodes four transcriptional regulators (MTLa1, a2, alpha 1, and alpha 2). The conserved a1/alpha 2 heterodimer controls not only mating competency but also whiteopaque heritable phenotypic switching. However, the regulatory roles of MTLa2 and alpha 1 are more complex and remain to be investigated. MTLa/a cells often express a cell type-specific genes and mate as the a-type partner, whereas MTL alpha/alpha cells express alpha-specific genes and mate as the alpha-type partner. In this study, we report that the MTLa2 regulator controls the formation of mating projections through both the a- and alpha-pheromone-sensing pathways and thus results in the bi-mater feature of alpha cells of C. albicans. Ectopic expression of MTLa2 in opaque alpha cells activates the expression of not only MFA1 and STE3 (a-pheromone receptor) but also MF alpha 1 and STE2 (alpha-pheromone receptor). Inactivation of either the MFa-Ste3 or MF alpha-Ste2 pheromone-sensing pathway cannot block the MTLa2-induced development of mating projections. However, the case is different in MTL alpha 1ectopically expressed opaque a cells. Inactivation of the MF alpha-Ste2 but not the MFa-Ste3 pheromone-sensing pathway blocks MTL alpha 1-induced development of mating projections. Therefore, MTLa2 and MTL alpha 1 exhibit distinct regulatory features that control the mating response in C. albicans. These findings shed new light on the regulatory mechanism of bi-mating behaviors and sexual reproduction in C. albicans.

Automated summary

The fungal pathogen Candida albicans has three configurations at the mating type locus, with MTLa2 and MTL alpha 1 exhibiting distinct regulatory features in controlling mating response. MTLa2 controls the formation of mating projections through both a- and alpha-pheromone-sensing pathways, while MTL alpha 1 is involved in the development of mating projections. These findings shed new light on the regulatory mechanism of bi-mating behaviors and sexual reproduction in C. albicans.