Transcriptome-Based Discovery of Fusarium graminearum Stress Responses to FgHV1 Infection

Fusarium graminearum hypovirus 1 (FgHV1), which is phylogenetically related to Cryphonectria hypovirus 1 (CHV1), is a virus in the family Hypoviridae that infects the plant pathogenic fungus F. graminearum. Although hypovirus FgHV1 infection does not attenuate the virulence of the host (hypovirulence), it results in defects in mycelial growth and spore production. We now report that the vertical transmission rate of FgHV1 through asexual spores reached 100%. Using RNA deep sequencing, we performed genome-wide expression analysis to reveal phenotype-related genes with expression changes in response to FgHV1 infection. A total of 378 genes were differentially expressed, suggesting that hypovirus infection causes a significant alteration of fungal gene expression. Nearly two times as many genes were up-regulated as were down-regulated. A differentially expressed gene enrichment analysis identified a number of important pathways. Metabolic processes, the ubiquitination system, and especially cellular redox regulation were the most affected categories in F. graminearum challenged with FgHV1. The p20, encoded by FgHV1 could induce H₂O₂ accumulation and hypersensitive response in Nicotiana benthamiana leaves. Moreover, hypovirus FgHV1 may regulate transcription factors and trigger the RNA silencing pathway in F. graminearum.