The Role Of MoPEX1 In Morphogenesis And Pathogenicity Of Magnaporthe Oryzae And Identification And Functional Analysis Of MoSom1 PKA Phosphorylation Site

Rice blast caused by Magnaporthe oryzae,is one of the most serious diseases of rice worldwide,which can destroy 40%to 50%of the rice harvest,even 100%.Therefore,in-depth study and analysis of pathogenic molecular mechanism of Magnaporthe oryzae is not only benefit for the development of new fungicides,but also serving a guiding significance for other plant-pathogenic fungi.Here,we report the identification of MoPEX1 in the infection-related morphogenesis and pathogenicity of Magnaporthe oryzae and the functional analysis of PKA phosphorylation sites of MoSoml.The results are listed as follows:1.MoPEXl is essential for infection-related morphogenesis and pathogenicity by the rice blast fungus Magnaporthe oryzae.Peroxisomes are required for pathogenicity in many phytopathogenic fungi,but the relationships between fungal pathogenicity and peroxisomal function are not fully understood.Here,we report the identification of a T-DNA insertional mutant C445 of Magnaporthe oryzae,which is defective in pathogenicity.Bioinformatics analysis revealed that the T-DNA in C445 was integrated at position 4280958+ on supercontig 18 of chromosome I,536 bp downstream of the predicted translational start site,in the second exon of MGG 09299.MGG₀9299 putatively encodes a protein homologous to Peroxin 1?Pexl?,and was thus assigned as MoPEX1 in the present work.Targeted gene deletion mutants of MoPEX1 were nonpathogenic and were impaired in vegetative growth,conidiation,and appressorium formation.?Mopexl mutants formed abnormal,less pigmented,and nonfunctional appressoria,but they were unable to penetrate plant cuticle.The ?Mopexl mutants were defective in the utilization of fatty acids?e.g.,olive oil and Tween-20?.Moreover,deletion of MoPEXl significantly impaired the mobilization and degradation of lipid droplets during appressorium development.Interestingly,deletion of MoPEX1 blocked the import of peroxisomal matrix proteins.Analysis of an M.oryzae strain expressing GFP-MoPEX1 and RFP-PTS1 fusions revealed that MoPex1 localizes to peroxisomes.Yeast two hybrid?Y2H?experiments showed that MoPexl physically interacts with MoPex6,a peroxisomal matrix protein important for fungal morphogenesis and pathogenicity.Taken together,we conclude that MoPEXl plays important roles in peroxisomal function and is required for infection-related morphogenesis and pathogenicity in M.oryzae.2.Phosphorylation of the 227th serine residue of Mosoml is essential for pathogenicity of the rice blast fungus.Bioinformatics analysis of MoSoml revealed that there were eight predicted PKA phosphorylation sites in MoSoml,and deletion and site-directed mutagenesis analyses showed that ?Mosom1/MoSOAM1S227V and ?Mosom1/MoSOM1s227Y mutants were non-pathogenic.In this study,we functionally analyzed the phenotype of the?Mosom1/MOSOM1s227v and ?Mosom1/MoSOM1S227Y mutants:?Mosom1/MoSOM1S227V and ?Mosom1/MoSOM1S227Y mutants lost the ability to infect the unwounded and abraded leaves of barley and rice and were ubable to produce conidia.These results indicated that the phosphorylation of serine residues at position 227 of MoSoml is essential for pathogenicity of the rice blast fungus.