WetA Is Required for Conidiogenesis and Conidium Maturation in the Ascomycete Fungus Fusarium graminearum

Abstract

ABSTRACTFusarium graminearum, a prominent fungal pathogen that infects major cereal crops, primarily utilizes asexual spores to spread disease. To understand the molecular mechanisms underlying conidiogenesis inF. graminearum, we functionally characterized theF. graminearumortholog ofAspergillus nidulanswetA, which has been shown to be involved in conidiogenesis and conidium maturation. Deletion ofF. graminearumwetAdid not alter mycelial growth, sexual development, or virulence, but thewetAdeletion mutants produced longer conidia with fewer septa, and the conidia were sensitive to acute stresses, such as oxidative stress and heat stress. Furthermore, the survival rate of aged conidia from theF. graminearumwetAdeletion mutants was reduced. ThewetAdeletion resulted in vigorous generation of single-celled conidia through autophagy-dependent microcycle conidiation, indicating that WetA functions to maintain conidial dormancy by suppressing microcycle conidiation inF. graminearum. Transcriptome analyses demonstrated that most of the putative conidiation-related genes are expressed constitutively and that only a few genes are specifically involved inF. graminearumconidiogenesis. The conserved and distinct roles identified for WetA inF. graminearumprovide new insights into the genetics of conidiation in filamentous fungi.