title: Pseudomonas syringae Effector AvrPphB Suppresses AvrB-Induced Activation of RPM1 but Not AvrRpm1-Induced Activation.
abstract: The Pseudomonas syringae effector AvrB triggers a hypersensitive resistance response in Arabidopsis and soybean plants expressing the disease resistance (R) proteins RPM1 and Rpg1b, respectively. In Arabidopsis, AvrB induces RPM1-interacting protein kinase (RIPK) to phosphorylate a disease regulator known as RIN4, which subsequently activates RPM1-mediated defenses. Here, we show that AvrPphB can suppress activation of RPM1 by AvrB and this suppression is correlated with the cleavage of RIPK by AvrPphB. Significantly, AvrPphB does not suppress activation of RPM1 by AvrRpm1, suggesting that RIPK is not required for AvrRpm1-induced modification of RIN4. This observation indicates that AvrB and AvrRpm1 recognition is mediated by different mechanisms in Arabidopsis, despite their recognition being determined by a single R protein. Moreover, AvrB recognition but not AvrRpm1 recognition is suppressed by AvrPphB in soybean, suggesting that AvrB recognition requires a similar molecular mechanism in soybean and Arabidopsis. In support of this, we found that phosphodeficient mutations in the soybean GmRIN4a and GmRIN4b proteins are sufficient to block Rpg1b-mediated hypersensitive response in transient assays in Nicotiana glutinosa. Taken together, our results indicate that AvrB and AvrPphB target a conserved defense signaling pathway in Arabidopsis and soybean that includes RIPK and RIN4.
authors.affiliation: Department of Biology, Indiana University, Bloomington, IN 47405, U.S.A.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Russell
authors.affiliation: Department of Biology, Indiana University, Bloomington, IN 47405, U.S.A.
authors.forename: Tom
authors.initials: T
authors.lastname: Ashfield
authors.affiliation: Department of Biology, Indiana University, Bloomington, IN 47405, U.S.A.
authors.forename: Roger W
authors.initials: RW
authors.lastname: Innes
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D047908:Intracellular Signaling Peptides and Proteins; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D010766:Phosphorylation; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D030821:Plants, Genetically Modified; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D044224:Pseudomonas syringae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction; D013025:Glycine max / Q000201:enzymology / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D014026:Nicotiana / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D019076:Transgenes
chemical_list: D029681:Arabidopsis Proteins; C100931:AvrB protein, Pseudomonas syringae; D001426:Bacterial Proteins; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; C453279:RIN4 protein, Arabidopsis; C095014:RPM1 protein, Arabidopsis; C500179:avrPphB protein, Pseudomonas syringae; D011494:Protein Kinases; C558451:RPM1-induced protein kinase, Arabidopsis