Functional Characterization Of Five Effectors In Phytophthora And Rastonia Solanacearum

To successfully infect and colonize host plant,pathogen secretes a series of effectors into the plant cells that promote its infection.These effectors play an important role during plant-pathogen interactions.Using Phytophthora capsici and Ralstonia solanacearum effectors as materials,in this study we aimed at elucidating virulence function and mechanism of these effectors,the results will help us understand mechanims of pathogen virulence.The main results are as follows:Identification and functional analysis of P.capsici effectors associating with four plant immune regulators.Salicylic acid(SA)is a key regulator of plant immunity,and NPR1,NPR3,NPR4,EDS1 play an important role in the SA signaling pathway.However,it is unclear whether effectors secreted by the oomycete pathogens target these proteins.In this study,using four plant immune regulators mentioned above as baits,their interacting RxLR effectors were identified from P.capsici,and we found that NPR1 potentially interacts with 16 effectors,NPR3 or NPR4 potentially interacts with PcAvh41,EDS1 potentially interacts with PcAvh103.Next their interactions were confirmed by yeast two-hybrid assay.We found that the P.capsici effector RxLR48 interacts with NPR1,and effector PcAvhl03 interacts with EDS1.Overexpression of RxLR48 and PcAvh103 in Nicotiana benthamiana enhances P.capsici infection respectively,indicating that both effectors contribute to virulence through targeting NPR1 and EDS1.In RxLR48-expressing Arabidopsis protoplasts,the transcription level of FRK1 was significantly reduced,suggesting that RxLR48 is able to suppress PTI signaling.Our research revealed the virulence functions and mechanisms of these two effectors,providing clues for understanding oomycete pathgenesis.Identification of plant targets and functional characterization of three R.solanacearum effectors.R.solanacearum strain GMI1000 secretes more than 70 effectors.However,the function of most effectors is unclear.Previous studies have shown that three effectors of GMI1000,Rip10,Rip11 and Rip12 induce hypersensitive response(HR)on N.benthamiana.In this study,we used these three effectors as baits,and screened for their interacting proteins in N.benthamiana.In total,5,4,and 108 candidate proteins were obtained,respectively.Furthermore,we confirmed that Rip 10 interacts with a BTB/POZ-domain containing protein;Ripll interacts with SGT1 and KLCR2;Rip12 interacts with 21 proteins,and most of them were proteases.The Ripll associated BTB/POZ domain-contianing protein,which we called it NbBTB,is uncharacterized protein.Overexpression of NbBTB in N.benthamiana enhanced resistance to P.parasitica,and silencing the NbBTB significantly reduced plant resistance to P.parasitica.Therefore,NbBTB positively regulates plant resistance.Moreover,We found that NbBTB not only promotes ROS burst,but also enchances Rip22-and Rip35-induced HR on N.benthamiana,further confirming that NbBTB plays an important role in plant immunity.However,its function mechanism needs further studies.