Analysis Of The Immune Activity And Virulence Function Of The PAMP PsXEG1 Secreted Byphytophthora Sojae

Root rot of soybean caused by Phytophthora sojae is one of the most destructivethreatsto soybean production in the world.This disease causes extremely significant economic losses every year and threats the yield of soybean all over the world.Because of therapid evolution ofP.sojae,most of the fungicides are not effective to control P.sojae.In this case,we need to find other ways to control the diseases.Inplant innate immunity,host receptors canrecognize conserved pathogen associated molecular patterns(PAMPs)and trigger defence responsesto defend themselves against microbial invasion.PAMPs were originally definedas highly conserved molecules that have an essential function in microbial fitness or survival within a class of microbes.Studies on the perceptionofoomycetes PAMP will provide the basis for understanding the plant resistance mechanism and finding out effectively disease resistance resources.Therefore,this study focus on the analysis of the immune activity and the virulence function of the PAMP PsXEG1 secreted by Phytophthora sojae.We found that the Glycoside Hydrolase 12 family can triger a series of denfense responses and thevirulence of PsXEGl depends on the hydrolytic enzyme activity.The main results are showed as follows:Analysis of the immune activity of Glycoside Hydrolase 12(GH12)proteins in oomycetes.In our previous work,we identified a novel PAMPin P.sojae named as XEG1.In order to analyze the immune activityofXEG1,we performed a series of studies.We find XEG1 can not only trigger cell death in Nicotiana benthamiana,but also induce the expression of defense-related genes,such asNbCyp71D20 and NbAcre31.XEG1 can also trigger ROS accumulation and callose depositionresponses.These responses are all typical PAMP-triggered immunities in plants.According to the bioinformatic analysis,XEG1 is an enzyme which can reduce sugars from both xyloglucan and(3-glucan.To study the phylogenetic distribution of XEG1 homologsin oomycete,we mined the genomes of 5 oomycete species.A total of 43 genesencoding homologous protein sequences were identified.The protein sequences of XEG1 and homologs containing GH12 domain predicted by the GenBank Conserved DomainDatabase,they all belong to the Glycoside Hydrolase 12 Family.To determine whether these diverse oomyceteGH12 proteins could trigger cell death in N.benthamiana,43 genes were testedby agroinfiltration.And we finda wide diversity of GH12 proteinsfrom different species could be recognized and trigger cell death in N.benthamiana.Analysis of the virulent function of PsXEGl in Phytophthora sojae.PsXEG1 belongs to the Glycoside Hydrolase 12 Family and hasthe hydrolytic enzyme activity whichcan degradexyloglucan and ?-glucan.In our previous work,we found PsXEG1 was expressed at high levels during very early infection stages,silencingof PsXEG1can reduceits virulence.As the CRISPR-Cas9 genome editing technology for P.sojae has been successful used,in order to further analysis the virulent mechanism of PsXEG1,we use the CRISPR-Cas9 system to knock out PsXEG1 and exchange PsXEG1 with GUS.Phenotypic analysis showed that knocking out PsXEG1 and exchanging PsXEGl with Gus does not affect the growth rate of P.sojae,but the pathogenicity of mutants are reduced compared with WT.When we exchange PsXEGl with PsXEG1E136D&E222D which does not have the hydrolase activity,we found the pathogenicity of mutants arealso reduced compared with WT.All in all,the virulence function of PsXEG1 depends onits hydrolytic enzyme activity.