Role Of Class Ⅰ Myosin Protein Momyo1 In Development And Pathogenicity Of Magnaporthe Oryzae

In eukaryotes organisms,myosin provides the necessary impetus for a series of physiological processes,including organelle movement,cytoplasmic flow,macromolecular transport,cell division and mitosis.Previously,three members of myosin were identified in Magnaporthe oryzae,with class-II and class-V myosins playing important roles in intracellular transport,fungal growth and pathogenicity.However,the biological roles of the class-I myosin protein remain unclear.Here,we firstly analyse the transcription profiles of class-I myosin-encoding gene at different developmental stages,and according to q RT-PCR,Momyo1 is highly expressed during conidial development and infectious stage.Next,two independent strategies were adopted to investigate the roles of Momyo1.The first attempt to generate a target gene deletion of Momyo1,proved unsuccessful,indicating that class-I myosin is essential for viability of M.oryzae.Secondly,conditional gene silencing of Momyo1 by RNA interference was employed and three silent mutants were obtained.Biological phenotypic analysis indicated that hyphae branch significant increase and the hyphae dry weight of mutants severely decreased in the mutants.Furthermore,the mutants lost the ability to generate conidia.q RT-PCR exhibited significantly down-regulated expression of conidiation associated genes,such as ACR1,Mossadh,Mohox2,Mo Stu A,FLBA,FLBC,FLBD and FLUG in the Momyo1 mutants.Pathogenicity test revealed that the mutants lost virulence on rice and barley.Microscopy examination indicated that the mutants could not form appressorium-like structures on the surface of rice leaves.Subsequent q RT-PCR revealed that the expression of six genes,such as Hox7,Pmk1,Pth11,Mac1,Mst11 and Mst50 involved in appressorium-like structures-like structures development significantly decreased in the mutants,compared to the wild-type Guy11.Beside of these phenotypes,the Momyo1 mutants also showed impairment in colony pigmentation,cell wall integrity,hyphal surface hydrophobicity,cell wall autolysis,extracellular enzyme activities and endocytosis.Furthermore,we identified that Momyo1 can physically interact with the actin cytoskeleton organization protein Mo She4,indicating that Momyo1 may affect cell morphology,endocytosis via breaking down the cytoskeleton of M.oryzae.Overall,our findings provide a novel insight into the regulatory mechanism of Momyo1 that is involved in fungal growth,cell wall integrity,endocytosis,and virulence of M.oryzae.