S-adenosyl-L-homocysteine hydrolase FgSah1 is required for fungal development and virulence in Fusarium graminearum

The S-adenosyl-L-homocysteine hydrolase (Sah1) plays a crucial role in methylation and lipid metabolism in yeast and mammals, yet its function remains elusive in filamentous fungi. In this study, we characterized Sah1 in the phytopathogenic fungus F. graminearum by generating knockout and knockout-complemented strains of FgSAH1. We found that the FgSah1-GFP fusion protein was localized to the cytoplasm, and that deletion of FgSAH1 resulted in defects in vegetative growth, asexual and sexual reproduction, stress responses, virulence, lipid metabolism, and tolerance against fungicides. Moreover, the accumulations of S-adenosyl-L-homocysteine (AdoHcy) and S-adenosyl-L-methionine (AdoMet) (the methyl group donor in most methyl transfer reactions) in ΔFgSah1 were seven- and ninefold higher than those in the wild-type strain, respectively. All of these defective phenotypes in ΔFgSah1 mutants were rescued by target gene complementation. Taken together, these results demonstrate that FgSah1 plays essential roles in methylation metabolism, fungal development, full virulence, multiple stress responses, lipid metabolism, and fungicide sensitivity in F. graminearum. To our knowledge, this is the first report on the systematic functional characterization of Sah1 in F. graminearum.