Identificationof The Components Required For XEG1-mediated Plant Immunity

Root rot of soybean caused by Phytophthora sojae is the most destructive disease to soybean production in the world.The disease causes extremely significant economic losses every year and threats the yield of soybean all over the world.P.sojae is an oomycete pathogen,which is phylogenetically distant from fungal pathogens but is related to diatoms.Controlling the diseases caused by oomycetes is usually not effective when using chemicals.In addition,the rapid evolution of avirulence genes in P.sojae leads to the loss of effective disease resistance in the breeding cultivars.Therefore,effectively control of the soybean root rot disease is still a big challengefor researchers.In plant-pathogen interactions,plants defend themselves against pathogen invasion by detecting conserved,secreted molecules,called pathogen-associated molecular patterns(PAMPs).PAMPs have an essential function in microbial fitness or survival within a class of microbes.In previous study,we identified a novel apoplastic elicitor(XEG1)from the soybean pathogen Phytophthora sojae.Exploration of the perception behind them will provide the basis for understanding the plant resistance mechanism and facilitate disease resistance breeding.Therefore,this study focus on the mechanism of the plant recognition of XEG1.The main results and conclusions are showed as follows:Co-receptors BAK1 and SOBIR1 are required for XEG1-triggered plant immunity.Previous study we identified a novel apoplastic elicitor(XEG1)from the soybean pathogen Phytophthora sojae.In this study,we want to kown whether XEG1 can induce plant immunity.XEG1 can induce cell death in N.benthamiana,but can not trigger cell death in NbBAK1-silenced N.benthamiana and triggers weaker cell death in NbSOBIR1-silenced N.benthamiana.These results show that BAK1 and SOBIR1 are involved in XEG1-triggered cell death.In addition,the defense-related gene expression can be inhibited in NbBAK1-silenced or NbSOBIR1-silenced N.benthamiana and inthebak1-3 or sobir1-12mutants of Arabidopsis.In summary,the co-recepters BAK1 and SOBIR1 participatein XEG1-induced cell death and the defense-related gene expression.Screening of the potential XEG1 targets in N.benthamiana using LC-MS.Many extracellular signals are detected by cell surface receptors and further transmitted inside the cell by forming receptor complexes.Previous study reveals that the LRR-receptor-like kinases BAK1 and SOBIR1 are essential components in plant pattern recognition receptor complexes.As we all known,during infecting plants,Phytophthora sojae can secret XEG1 which can be detected by plant pattern recognition receptorto trigger plant defense response in order to protect themselves against pathogens.We have proven that BAK1 and SOBIR1 are participated in induction of plant immunity by XEG1 in Nicotiana benthamiana.We have found that co-receptor SOBIR1 can interact with XEG1 by Co-IP in Nicotiana benthamiana.So we use BAK1 and SOBIR1 as baits in order to find the XEG1 potential targets in N.benthamiana using LC-MS(Mass spectrometry).The protein,isolated from leaves of N.bentha,miana,was purified by mixing total protein lysates with anti-GFP beads,and the bead-bound proteins were analyzed by MS.From the MS results,we finally got a series of putative BAK1-,SOBIR1-binding proteins.Several BAK1 potential targets were identified,such as a protein kinase which we called R2.Physical interactions of BAK1 with R2 were detected by Co-IP in vivo.We find R2 can not interact with BAK1,the reason may be that they do not have interaction between each other,but also may be R2 does not express or express very low.