Suppression of plant-generated reactive oxygen species is required for successful infection by the rice blast fungus.

Magnaporthe oryzae is a filamentous ascomycete that continuously threatens global rice production. The infection cycle of this pathogen commences with the attachment of conidia to rice plants, followed by the formation and maturation of a specialized infection structure-the appressorium. Melanized appressoria generate immense turgor pressure, which allows the fungus to break through the plant cuticle and cell wall by means of a penetration peg. These stages occur within the first twenty-four hours after which time the penetration peg gives rise to and subsequent primary and secondary infection hyphae. Upon infection, the plant recognizes the pathogen, triggering a series of defense responses and signaling events including the secretion of reactive oxygen species (ROS). In a recent paper, we showed that barley plants generate ROS and cell wall appositions (CWAs) around infection sites and that a fungal gene we termed MoHYR1 is necessary for ameliorating these defense reactions and ensuring successful infection and colonization. When this gene is deleted from the M. oryzae genome, the plant oxidative responses are stronger and disease is reduced.