Two Putative Pheromone Receptors, but Not Their Cognate Pheromones, Regulate Female Fertility in the Atypical Mating Fungus .

fungi are a group of damaging phytopathogens with atypical mating type loci (harboring only but not ) and complex sexual behaviors. Sex pheromones and their cognate G-protein-coupled receptors are conserved regulators of fungal mating. These genes, however, lose function frequently among species, indicating a possibility that pheromone signaling is dispensable for sexual reproduction. We have identified two putative pheromone-receptor pairs (PPG1:PRE2, PPG2:PRE1) in , a species that exhibits plus-to-minus mating type switching and plus-minus-mediated mating line development. Here, we report the generation and characterization of gene-deletion mutants for all four genes in both plus and minus strain backgrounds. Single-gene deletion of or had no effect on sexual development, whereas their double deletion caused self-sterility in both the plus and minus strains. Moreover, double deletion of and caused female sterility in plus-minus outcrossing. Double deletion of and , however, did not inhibit perithecial differentiation or plus-minus-mediated enhancement of perithecial differentiation. Contrary to the results with and , double deletion of and had no effect on sexual compatibility, development, or fecundity. We concluded that and coordinately regulate mating by recognizing novel signal molecule(s) distinct from canonical Ascomycota pheromones. The contrasting importance between pheromone receptors and their cognate pheromones highlights the complicated nature of sex regulation in fungi.