The Lipoxygenase Lox1 Is Involved in Light- and Injury-Response, Conidiation, and Volatile Organic Compound Biosynthesis in the Mycoparasitic Fungus Trichoderma atroviride

The necrotrophic mycoparasiteTrichoderma atrovirideis a biological pest control agent frequently applied in agriculture for the protection of plants against fungal phytopathogens. One of the main secondary metabolites produced by this fungus is 6-pentyl-alpha-pyrone (6-PP). 6-PP is an organic compound with antifungal and plant growth-promoting activities, whose biosynthesis was previously proposed to involve a lipoxygenase (Lox). In this study, we investigated the role of the single lipoxygenase-encoding genelox1encoded in theT. atroviridegenome by targeted gene deletion. We found that light inhibits 6-PP biosynthesis butlox1is dispensable for 6-PP production as well as for the ability ofT. atrovirideto parasitize and antagonize host fungi. However, we found Lox1 to be involved inT. atrovirideconidiation in darkness, in injury-response, in the production of several metabolites, including oxylipins and volatile organic compounds, as well as in the induction of systemic resistance against the plant-pathogenic fungusBotrytis cinereainArabidopsis thalianaplants. Our findings give novel insights into the roles of a fungal Ile-group lipoxygenase and expand the understanding of a light-dependent role of these enzymes.