Molecular Mechanism Of Inhibition Of MdPR10-mediated Immune Response In Malus Domestic By VmEp1,An Effector Protein Of Apple Valsa Canker

Apple Valsa canker,induced by the fungus Valsa mali,is a serious concern for the apple industry.The fungus exclusively attacks the bark of the established trees,causing necrosis and resulting in a serious reduction in fruit quality and yield.An in-depth study and understanding of the pathogenesis of the fungus is an important approach to develop integrated prevention and control technologies for apple Valsa canker.Preliminary laboratory studies revealed that the V.mali effector Vm Ep1 promotes pathogen infestation by targeting the apple PR10 protein and inhibiting PR10-mediated plant immunity.However,the molecular mechanism by which Vm Ep1 affects PR10 protein function is unclear.In this study,we used the apple LRR-only protein MdLRR2 to verify the interaction between MdLRR2 and MdPR10 using yeast two-hybrid assay,luciferase complementation assay and micro-scale thermophoresis,investigated the mechanism by which Vm Ep1 interferes with the protein interaction between MdLRR2 and MdPR10.The main conclusions are as follows:MdLRR2 is a positive regulator of plant disease resistance.Overexpression of MdLRR2 significantly up-regulated the expression of immune-related genes such as salicylic acid,reactive oxygen species and phyto-defensins,promoted the accumulation of plant callose,and thus enhancing plant resistance to the apple Valsa canker.MdLRR2 has protein interactions with MdPR10.MdLRR2 enhances MdPR10-mediated disease resistance by increasing the RNase activity of MdPR10 through interactions with MdLRR2.Vm Ep1 competes with MdLRR2 to bind MdPR10.By competing with MdLRR2 to bind MdPR10,Vm Ep1 interferes with the interaction of MdLRR2 with MdPR10,thereby affecting the RNase activity of MdRP10 and MdPR10-induced callose accumulation as well as plant disease resistance.In summary,the effector protein Vm Ep1 inhibited the PR10-mediated plant immune response by interfering with the protein interaction between MdLRR2 and MdPR10,which affected the RNase activity of MdPR10 protein.