High-throughput FACS-based mutant screen identifies a gain-of-function allele of the Fusarium graminearum adenylyl cyclase causing deoxynivalenol over-production

Fusarium head blight and crown rot, caused by the fungal plant pathogen Fusarium graminearum, impose a major threat to global wheat production. During the infection, plants are contaminated with mycotoxins such as deoxynivalenol (DON), which can be toxic for humans and animals. In addition, DON is a major virulence factor during wheat infection. However, it is not fully understood how DON production is regulated in F. graminearum. In order to identify regulators of DON production, a high-throughput mutant screen using Fluorescence Activated Cell Sorting (FACS) of a mutagenised TRI5-GFP reporter strain was established and a mutant over-producing DON under repressive conditions identified. A gain-of-function mutation in the F. graminearum adenylyl cyclase (FAC1), which is a known positive regulator of DON production, was identified as the cause of this phenotype through genome sequencing and segregation analysis. Our results show that the high-throughput mutant screening procedure developed here can be applied for identification of fungal proteins involved in diverse processes.