FgPKS7 is an essential player in mating-type-mediated regulatory pathway required for completing sexual cycle in Fusarium graminearum

Abstract

Secondary metabolism is intimately linked to developmental processes in filamentous fungi. In a previous study, we revealed that several polyketide synthase (PKS) genes, including FgPKS7, are specifically induced during formation of the sexual fruiting body (perithecium) in the cereal pathogen Fusarium graminearum. The function of PKS7, which is essential for perithecial development and hyphal growth, is interchangeable between two phylogenetically related species, F. graminearum and F. asiaticum, but not conserved in the more distantly related species F. fujikuroi and F. neocosmosporiellum. FgPKS7 is under the control of global or upstream regulators including the mating-type (MAT) locus and regulates numerous downstream genes that are transcriptionally specific to and functionally essential for sexual development, several other PKS genes, and ABC transporter genes for azole resistance in F. graminearum. FgPKS7 is an essential element for proper sexual development and participates in a regulatory network controlled by the MAT locus. Although the chemical identity of FgPKS7 remains unclear, FgPKS7 is likely involved in chemical reaction(s) for synthesis of metabolite(s) that control or promote perithecial maturation in F. graminearum. This study provides in-depth insights into the direct role of secondary metabolites in sexual development of filamentous fungi.