A putative pheromone signaling pathway is dispensable for self-fertility in the homothallic ascomycete Gibberella zeae

Abstract

Gibberella zeae, a homothallic ascomycetous fungus, does not seek a partner for mating. Here, we focused on the role(s) of putative pheromone and receptor genes during sexual development in G. zeae. Orthologs of two pheromone precursor genes ( GzPPG1 and GzPPG2), and their cognate receptor genes ( GzPRE2 and GzPRE1) were transcribed during sexual development . The expression of these genes was controlled by the mating-type ( MAT) locus and a MAP kinase gene, but not in a MAT-specific manner. Targeted gene deletion and subsequent outcrosses generated G. zeae strains lacking these putative pheromone/receptor genes in various combinations (from single to quadruple deletions). All G. zeae deletion strains were similar to the self-fertile progenitor in both male- and female fertility and other traits. Sometimes, the deletions including Δ GzPPG1;Δ GzPRE2 caused increased numbers of immature perithecia. Taken together, it is clear that these putative pheromones/receptors play a non-essential role in the sexual development of G. zeae.