MoNFR, encoding a putative NADPH-ferrihemoprotein reductase, is required for the pathogenicity of Magnaporthe oryzae

Abstract A wild type Magnaporthe oryzae CY2 with normal growth and sporulation but weak pathogenicity is not virulent to more than over 1000 rice cultivars. Based on the transformant library of M. oryzae CY2 by Agrobacterium tumefaciens-mediated transformation (ATMT), we screened a transformant T23 with normal infectious hyphae and pathogenicity to rice line IRBL-19. Co-segregation and southern blotting suggested that T-DNA is inserted with single copy, and pathogenicity may require the mutated gene MoNFR. Bioinformatics analysis predicted that the gene MoNFR encoded a putative NADPH-ferrihemoprotein reductase with an indole amine 2,3-dioxgyenase (IDO) domain, a flavin adenine dinucleotide binding domain (FAD_binding domain), a nicotinamide adenine dinucleotide binding domain (NAD_binding domain) and a cytochrome-b5 domain. Vectors were constructed to knock-out the target gene. Two mutants with MoNFR disruptant were obtained from the wild type strain CY2 by targeted gene replacement with hygromycin B phosphotransferase (HPH) gene. Compared with strain T23 and CY2, the MoNFR mutants showed no significant difference in colony morphology, growth rate and mycelium color but conidia produced in culture were 4.5–5 times more and higher percentage of appressorial and infectious hyphae formation was observed on onion epidermis. They retain the pathogenicity to IRBL-19, and are similar in virulence to strain T23. These results indicate that MoNFR plays a key role in the pathogenicity of M. oryzae.