Molecular Mechanism Of Plant Resistance Induced By Ralstonia Solanacearum Elicitor PopA

Bacterial wilt disease is a soil-borne disease caused by Ralstonia solanacearum pathogen.A severe loss of production has been caused by this disease due to the lack of effective control strategy.R.solanacearum infects a wide range of hosts,entering into xylem through the root.R.solanacearum occupies the vascular in adis of the rich extracellular polysaccharides,leading to a block of water transportation and finally causing the wilt symptoms on plant.The type Ⅲ secretion system is a key virulence factor,determining the pathogenicity on hosts.The harpin-like protein PopA is secreted by type Ⅲ secretion system,acting as an elicitor to induce HR responses in petunia and tobacco plants.Furthermore,PopA is processed into three different sizes by pathogen: full length PopA(PopA1),PopA2,and PopA3.This thesis aims to clone and characterize PopA-interacting proteins and their roles in recognizing PopA to trigger defense reaction.Transient expression of PopA on N.benthamiana leaves induced the yellowing phenotype,coupled with the activation of defense response.Through yeast two-hybrid and luciferase complementation experiments,the mitochondrial ATP synthase F1 subunit α(ATPA)was identified as PopA-interacting protein from tobacco.RFP-PopA1 was located at cell membrane and cytoplasm,meanwhile GFP-ATPA was localized in the cell membrane,cytoplasm,and nucleus,as well as in mitochondria.RFP-PopA1 and GFP-ATPA were co-localized at the cell membrane and cytoplasm.A bimolecular fluorescence complementation revealed that ATPA interacted with Rip X at both the cell membrane and cytoplasm in vivo.Out of expected,gene silencing of atpA promoted resistance to R.solanacearum.Transient expression of PopA repressed the transcriptional expression of atpA gene.This thesis examined the defense induction of PopA in N.benthamiana and cloned the interacting protein ATPA.Gene silencing demonstrated that atpA is involved in plant susceptibility.These results reported the molecular mechanism in association with defense induction by PopA,which will provide a clue for plant defense breeding.