title: Identification of Pseudomonas syringae type III effectors that can suppress programmed cell death in plants and yeast.
abstract: The Pseudomonas syringae pv. tomato DC3000 type III secretion system (TTSS) is required for bacterial pathogenicity on plants and elicitation of the hypersensitive response (HR), a programmed cell death (PCD) that occurs on resistant plants. Cosmid pHIR11 enables non-pathogens to elicit an HR dependent upon the TTSS and the effector HopPsyA. We used pHIR11 to determine that effectors HopPtoE, avirulence AvrPphEPto, AvrPpiB1Pto, AvrPtoB, and HopPtoF could suppress a HopPsyA-dependent HR on tobacco and Arabidopsis. Mixed inoculum and Agrobacterium-mediated transient expression experiments confirmed that suppressor action occurred within plant cells. These suppressors, with the exception of AvrPpiB1Pto, inhibited the expression of the tobacco pathogenesis-related (PR) gene PR1a. DC3000 suppressor mutants elicited an enhanced HR consistent with these mutants lacking an HR suppressor. Additionally, HopPtoG was identified as a suppressor on the basis of an enhanced HR produced by a hopPtoG mutant. Remarkably, these proteins functioned to inhibit the ability of the pro-apoptotic protein, Bax to induce PCD in plants and yeast, indicating that these effectors function as anti-PCD proteins in a trans-kingdom manner. The high proportion of effectors that suppress PCD suggests that suppressing plant immunity is one of the primary roles for DC3000 effectors and a central requirement for P. syringae pathogenesis.
authors.affiliation: Plant Science Initiative and Department of Plant Pathology, University of Nebraska, Lincoln, NE 68588-0660, USA.
authors.forename: Yashitola
authors.initials: Y
authors.lastname: Jamir
authors.forename: Ming
authors.initials: M
authors.lastname: Guo
authors.forename: Hye-Sook
authors.initials: HS
authors.lastname: Oh
authors.forename: Tanja
authors.initials: T
authors.lastname: Petnicki-Ocwieja
authors.forename: Shaorong
authors.initials: S
authors.lastname: Chen
authors.forename: Xiaoyang
authors.initials: X
authors.lastname: Tang
authors.forename: Martin B
authors.initials: MB
authors.lastname: Dickman
authors.forename: Alan
authors.initials: A
authors.lastname: Collmer
authors.forename: James R
authors.initials: JR
authors.lastname: Alfano
mesh_terms: D017209:Apoptosis / Q000235:genetics / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D018506:Gene Expression Regulation, Plant; D007113:Immunity, Innate / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics; D010957:Plasmids / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2; D044224:Pseudomonas syringae / Q000472:pathogenicity*; D012231:Rhizobium / Q000235:genetics / Q000254:growth & development; D017384:Sequence Deletion; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D014774:Virulence; D015003:Yeasts / Q000235:genetics / Q000502:physiology*; D051028:bcl-2-Associated X Protein
chemical_list: D001426:Bacterial Proteins; D010940:Plant Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; C081695:avrPto protein, Pseudomonas syringae; D051028:bcl-2-Associated X Protein; C053376:pathogenesis-related proteins, plant