Molecular analysis of CPRα, a MATα-specific pheromone receptor gene of Cryptococcus neoformans

The putative Cryptococcus neoformans pheromone receptor gene CPRalpha was isolated and studied for its role in mating and filamentation. CPRalpha is MATalpha specific and located adjacent to STE12alpha at the MATalpha locus. It encodes a protein which possesses high sequence similarity to the seven-transmembrane class of G-protein-coupled pheromone receptors reported for other basidiomycetous fungi. Strains containing a deletion of the CPRalpha gene exhibited drastic reductions in mating efficiency but were not completely sterile. Deltacpralpha cells displayed wild-type mating efficiency when reconstituted with the wild-type CPRalpha gene. Hyphal production on filament agar was not affected in the Deltacpralpha strain, indicating no significant role for CPRa in sensing environmental cues during haploid fruiting. The wild-type MATalpha CPRalpha strain produced abundant hyphae in response to synthetic MATa pheromone; however, the hyphal response to pheromone by Deltacpralpha cells was significantly reduced. Exposure of wild-type cells to synthetic MATa pheromone for 2 h induced MFalpha pheromone expression, whereas unexposed cells showed only basal levels of the MFalpha transcript. The Deltacpralpha cells, however, exhibited only basal levels of MFalpha message with or without pheromone exposure, suggesting that CPRalpha and MFalpha are components of the same signaling pathway.