A pheromone receptor gene, pre‐1, is essential for mating type‐specific directional growth and fusion of trichogynes and female fertility in Neurospora crassa

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Abstract
Summary: Neurospora crassa is a heterothallic filamentous fungus with two mating types, mat a and mat A. Its mating involves differentiation of female reproductive structures (protoperithecia) and chemotropic growth of female‐specific hyphae (trichogynes) towards a cell of the opposite mating type in a pheromone‐mediated process. In this study, we characterize the pre‐1 gene, encoding a predicted G‐protein‐coupled receptor with sequence similarity to fungal pheromone receptors. pre‐1 is most highly expressed in mat A strains under mating conditions, but low levels can also be detected in mat a strains. Analysis of pre‐1 deletion mutants showed that loss of pre‐1 does not greatly affect vegetative growth, heterokaryon formation or male fertility in either mating type. Protoperithecia from Δpre‐1 mat A mutants do not undergo fertilization; this defect largely stems from an inability of their trichogynes to recognize and fuse with mat a cells. Previous work has demonstrated that the Gα subunit, GNA‐1, and the Gβ protein, GNB‐1, are essential for female fertility in N. crassa. Trichogynes of Δgna‐1 and Δgnb‐1 mutants displayed severe defects in growth towards and fusion with male cells, similar to that of Δpre‐1 mat A strains. However, the female sterility defect of the Δpre‐1 mat A mutant could not be complemented by constitutive activation of gna‐1, suggesting additional layers of regulation. We propose that PRE‐1 is a pheromone receptor coupled to GNA‐1 that is essential for the mating of mat A strains as females, consistent with a role in launching the pheromone response pathway in N. crassa.