Molecular Mechanism Of Momyo2 In Development And Pathogenicity Of Magnaporthe Oryzae

Rice blast disease caused by Magnaporthe oryzae is known as ‘cancer’ on rice and is a devastating fungal diseases in rice cultivation.To date,control measures of rice blast disease majorly focuse on resistant rice cultivars.Under natural conditions,due to the variable pathogenicity of the pathogenic bacteria,which will lead to the new rice disease-resistant varieties will be invalid in the short term of promotion.Therefore,the prevention and cure of Magnaporthe oryzae is still a major problem in rice production.And to learn about the growth and development of the pathogen as well as the pathogenesis of this fungi is the premise to prevent and cure the disease.This paper mainly studies the funcation of during the growth and the pathogenesis of Magnaporthe oryzae.The result is as followed:In this study,a mutant（A115）was identified to show reduced virulence from a T-DNA insertional mutagenesis library.Southern blot analysis revealed that A115 mutant contained a singlecopy（> 10 kb）insertion of hygromycin cassettes in the genome.TAIL-PCR was used to identify flanking sequences of T-DNA insertion in A115 mutant.Sequence analysis revealed an insertion of T-DNA into the second exon of MGG₀3060（GenBank XP₀03720621）.Amino acid sequence analysis of MGG₀3060 revealed several conserved domains,including an N-terminal SH3-like fold,N-terminal myosin motor domain（ATPase activity）,IQ motif（light chain and calmodulin binding site）and a coiled-coil tail（cellular localization）,which are characteristic structures identified in class II myosins in most fungi.Therefore,MGG₀3060 was designated as Momyo2.The results showed that Momyo2 gene is recruited to form a constricted contractile ring toward the middle of the septum.According to qRT-PCR,Momyo2 is highly expressed during early infectious stage.When this gene was disrupted,the resultant mutant isolates were attenuated in virulence on rice and barley.These were likely caused by defective mycelial growth and frequent emergence of branch hyphae and septum.The Momyo2 mutants were also defective in conidial and appressorial development,characterized by abnormal conidia and appressoria.Furthermore,impairments in conidial germination,glycogen metabolites,tolerance to exogenous stresses and scavenging of host-derived reactive oxygen species were associated with defects on appressorium mediated penetration,and therefore attenuated the virulence of Momyo2 mutants.Taken together,these results suggest that Momyo2 plays pleiotropic roles in fungal development,and is required for the full pathogenicity of Magnaporthe oryzae.