Machanisms Of Development And Pathogenesis Regulated By O-mannosyltransferase MoPmt4 In Magnaporthe Oryzae

Rice blast is one of the most devastating diseases in rice cultivation.It is caused by the infection of the ascomycete fungus Magnaporthe oryzae.At present,due to its economic importance and the genetic tractability of fungi and host,the pathogenic system of M.oryzae has become an ideal model organism for studying fungal-plant interactions.The genetic map and the draft of the whole genome sequence of M.oryzae have been clarified.These results provide a convenient way to study the relationship between between rice and M.oryzae.At present,three Pmt genes encoding O-mannosytransferase protein（PMT）have been identified in M.oryzae.Among them,MoPmt2 is classified into the Pmt2 subfamily and plays an important role in fungal growth and development and pathogenicity to rice.However,the biological functions of other Pmt proteins remain unclear.In the previous study,we have obtained the deletion mutants of the other two Pmt genes MoPmtl（MGG₀2954）and MoPmt4（MGG₀4427）.The virality of the Pmt4 subfamily member MoPmt4 was found to be decreased.In order to clarify its regulatory mechanism,the biological phenotype and the process of infection and pathogenesis were studied in detail in this research.The main results are as follows:This study found that MoPmt4 can complement the Pmt activity lacking in the S.cerevisiae ogm4 mutant strain.MoPmt4 expressed the highest amount in the conidia stage,followed by the initial 24 h of infection,and then gradually decreased.Phenotypic analysis showed that the loss of MoPmt4 gene can lead to growth retardation,increased mycelial branching,and vegetative propagation defects.The number of conidia in the MoPmt4 mutant increased,and the tolerance of conidia to H2O2 was reduced.MoPmt4 is involved in the regulation of conidial germination and attachment cell development of M.oryzae and plays a key role in regulating intracellular glycogen and lipid metabolism.After treatment with different penetrants,the MoPmt4 mutant increased the percentage of adherent endoplasmic wall separation,and the cell wall morphology was observed under transmission electron microscopy,indicating that the loss of MoPmt4 caused damage to CWI（cell wall integrity）of M.oryzae.Plant infection test results showed that the MoPmt4 deletion mutant reduced the ability of ROS to degrade and promoted infection by inhibiting host-generated ROS.A co-expression strain of RFP-HEEL and MoPmt4-eGFP was constructed,and co-localization of MoPmt4 with endoplasmic reticulum Marker was observed,indicating that the protein is localized in the endoplasmic reticulum.The deletion mutant of the domain was constructed,and the PMT domain in MoPmt4 was identified to play a decisive role in the growth and pathogenicity of M.oryzae.In summary,O-mannosylation protein mediated by MoPmt4 plays an important role in the growth and development,CWI and virus-producing effects of M.oryzae.The results provide a theoretical basis for finding new fungicide targets for inhibiting Magnaporthe oryza and designing new rice blast control strategies.