Functional Analysis Of Six RxLR Effectors In Phytophthora Capsici And One CRN Effector In Phytophthora Sojae

The Phytophthora can infect almost all kinds of dicotyledonous plants resulting in destructive damage to agriculture,forestry and ecological environment.Phytophthora capsici and Phytophthora sojae play important roles in such kind of pathogens which will secrete a large number of effectors to promote further infection.RxLR and CRN are the major effectors.In this study,we analyzed the function of six PcRxLR effectors and a PsCRN effector and preliminary revealed the roles of these effectors played in pathogenesis.The main results are as follows:Identification and functional analysis of homologous genes of RxLR242 in P.capsici:Interactions between a single RxLR effector in P.capsici and hosts or non-hosts are rarely reported.It has reported that RxLR242 can induce cell death and RxLR242-silenced transformants can increase pathogenicity of P.capsici in N.benthamiana that as a host,and can infect N.tabacum that as a nonhost.Here we identified fourteen homologous genes of RxLR242,but only encoding seven homologous proteins of RxLR242.Then transient expressed the seven proteins in N.benthamiana and N.tabacum.We found that five can induce cell death but two not.At the same time,through the analysis of the protein sequences,we found that the activity differentiation in cell death inducing is probably due to NO.101 amino acid mutant from leucine to arginine happened.Further study showed that two no cell death inducing proteins could suppress those five proteins from inducing cell death.Results show that RxLR242 is polymorphic in different P.capsici strains.There is a cell death inducing activity differentiation in RxLR242 homologues proteins because of a single amino acid mutations.No cell death induing proteins can suppress activities of those can induce cell death.Functional analysis of five RxLR effectors in P.capsici:It is not clear yet that the roles of these P.capsici.effectors in virulence.Result of transient expression in tobaco showed RxLR22,RxLR25 and RxLR103 could induce cell death,Identification by yeast two-hybrid system,it revealed RxLR103,RxLR48,RxLR172 interacted with defense-related proteins.To detect the contribution of the five RxLR effectors genes to P.capsici virulence,stable silencing of these effectors genes in P.capsici was carried out by polyethylene glycol(PEG)-mediated transformation method with the sense construct the five effectors genes.Pathogenicity analysis and hyphal colonization test showed that the virulence of P.capsici was significantly reduced after silencing these 5 genes.All data indicated that five RxLR effectors played a significant virulent role during infection.PsCRN161 may improve plants toleration to biotic and abiotic stresses by up-regulating defense-related genes:Based on previous study PsCRN161 located in nucleus.of P.sojae has cell death suppression activity.The resistance,tolerance to salinity and drought stresses of PsCRN161 transgenic plants was enhanced.But the mechanisms is not clear,To elucidate preliminarily the mechanisms,digital gene expression(DGE)analysis showed that defense-related genes including ABC transporters,Cyt P450 and receptor-like kinases(RLKs)were significantly up-regulated in PsCRN161-transgenic plants compared with GFP(green fluorescent protein)lines which implyed that PsCRN161 may increase the tolerance to biotic and abiotic stresses by up-regulating defense-related genes.