Magnaporthe Oryzae Effector MoSef1-mediated Immunosuppression And Its Degradation In Rice

Magnaporthe oryzae is a pathogenic fungus that causes the severe occurrence of rice blast and threatens the yield and safety of rice in the world.With the increasing world population,the demand for rice is increasing day by day.Therefore,controlling the outbreak of rice blast is the premise of safe production of rice.In the interaction between pathogens and plants,pathogens secrete a large number of effector molecules into the host to inhibit host immune response,and promote pathogens to infect host plants and achieve successful colonization.Previous studies in our laboratory found that MoSwa2 regulates the secretion of effector proteins that inhibit the immune response of host and promote the successful infection on rice by M.oryzae.In the mass spectrometric analysis of extracellular fluid proteins during appressorium formation of M.oryzae,it was found that the cofactor MoSwa2 could regulate the secretion of a series of extracellular redox proteins,and we successful identified an apoplast effector MoSef1 with oxidase activity,and its deletion mutation would lead to a significant decrease in virulence.The infected hyphae could not expand normally in rice leaf sheath cells and could not scavenge the reactive oxygen species produced by host cells.After predicting the protein domain of MoSef1,it was found that MoSEF1 encodes an extracellular berberine bridging enzyme protein(BBE-like),including an N-terminal signal peptide,three chitin-binding domains,a FAD-binding domain and a C-terminal BBE-binding domain.It has been reported that BBEs protein is related to polysaccharide oxidation in plants and fungi.In order to verify that MoSef1 can indeed oxidize polysaccharides,we performed MST assay,it is found that MoSef1 has the ability to binding β-1,3-glucan.Furthermore,the oxidation of β-glucan with different bond types was tested,and it was found that MoSef1 had the strongest oxidation ability to β-1,3-glucan.In addition,MoSef1 can oxidize β-1,3-glucan and weaken its ability to stimulate host immune response.The interaction between M.oryzae and rice has been in a state of "arms race" for a long time.Since MoSef1 can reduce the immune response of the host,the host may in turn inhibit the function of MoSef1 so as to improve the resistance.In this manuscript,the c DNA library of rice interacting with M.oryzae was screened by yeast two-hybrid,and a series of apoplast cysteine proteases interacting with MoSef1 were identified.The one-to-one interaction assay showed that ten of them could interact with MoSef1.At the same time,it was found that cysteine protease could cleave MoSef1,and inhibit the activity of MoSef1,so that rice could recognize cysteine-glucan normally,re-establish immune response and inhibit the infection of bacteria.Taken together,this study revealed the molecular mechanism of MoSef1,a new effector of M oryzae,inhibiting host immunity and promoting pathogen infection.And elucidated the molecular mechanism of rice improving disease resistance by interfering with MoSef1 activity via apoplast protease.The results are expected to expand scholar’s understanding of the interaction mechanism between plants and pathogens,and provide reference for the genetics and breeding of blast resistance and the research and development of new fungicides.