RESEARCH ARTICLE An S-(Hydroxymethyl)Glutathione Dehydrogenase Is Involved in Conidiation and Full Virulence in the Rice Blast Fungus

Magnaporthe oryzae is a hemibiotrophic fungal pathogen that causes rice blast disease. A compatible interaction requires overcoming plant defense responses to initiate colonization during the early infection process. Nitric oxide (NO) plays important roles in defense re-sponses during host-pathogen interactions. Microbes generally protect themselves against NO-induced damage by using enzymes. Here, we characterized an S-(hydroxymethyl)- glu-tathione dehydrogenase gene inM. oryzae,MoSFA1, the homologs of which are involved in NOmetabolism by specifically catalyzing the reduction of S-nitrosoglutathione (GSNO) in yeasts and plants. As expected from the activities of S-(hydroxymethyl)glutathione dehydro-genase in formaldehyde detoxification and GSNO reduction,MoSFA1 deletion mutants were lethal in formaldehyde containing medium, sensitive to exogenous NO and exhibited a higher level of S-nitrosothiols (SNOs) than that of the wild type. Notably, the mutants showed severe reduction of conidiation and appressoria turgor pressure, as well as signifi-cantly attenuated the virulence on rice cultivar CO-39. However, the virulence ofMoSFA1 deletion mutants on wounded rice leaf was not affected. An infection assay on barley lea