The Deletion Mutant Construction And Biological Phenotype Analysis Of F-box Gene In Magnaporthe Oryzae

The filamentous ascomycete fungus Magnaporthe oryzae is one of the most destructive phytopathogen of rice plants, which severely threats the rice yield worldwide. Recently, the identification of the pathogenitic gene was accelerated due to the release of the fungus genome, and the investigation of interactions mechanism between the fungus and the rice plants makes it serve as an ideal model for studying molecular plant-pathogen interactions. In addition, understanding the fungus development and pathogenesis of M. oryzae on molecular level is a prerequisite to provide novel strategies for disease management and rice quality enhancement.We characterized an F-box protein Mofbox, a homolog of F-box in Saccharomyces cerevisiae in M. oryzae. The F-box possessed a typical F-box domain at the amino terminus and nuclear localization signal（KTKR）at the carboxyl terminus. The gene knocking out vector was constructed and transformed into M. oryzae, and two gene deletion mutants were obtained by the principle of homologous recombination. Studies on the biological characteristics showed that the mycelial growth rate of the Mofbox mutant reduced10.0%, compared with the wild type Guy11strain. The tolerance to NaCl, SDS and H₂O₂were decreased5.0%、6.0%and17.0%, but tolerance to CFW and CR were increased2.5%and4.1%respectively. Pathogenicity assay showed that the Mofbox mutants attenuated virulence on both barly and rice cultivar CO-39. A further investigation revealed55.0%and52.0%reduction of conidiation of the mutants, compared with the wild type Guy11respectively. The appressoria formation rate on hydrophobic surface was significantly reduced and turgor pressure in those appressoria also significantly declined, compared with the wild-type strain. Appressoria penetration assay on onion epidermal cells showed that the penetration rate of mutants has significantly reduced, with less penetration rate38.0%than the wild type strain. Meanwhile, among those penetrated appressoria, most invasive mycelium showed incapable of extending in onion epidermal cells. At the same time, the transcriptional level of Rho3、M ST11、M ST50、P MK1andMPG1gene participated in appressoria formation showed significantly decreased expression compared with the wild-type strain.In conclusion, the Mofbox protein has an important role in regulation of mycelium growth rate, sporulation, exogenous oxidative stress tolerance, appressoria formation and pathogenicity of M. oryzae.