Identification of Pseudomonas syringae type III effectors that can suppress programmed cell death in plants and yeast

Plant J. 2004 Feb;37(4):554-65. doi: 10.1046/j.1365-313x.2003.01982.x.

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.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Apoptosis / genetics
  • Apoptosis / physiology*
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Gene Expression Regulation, Bacterial
  • Gene Expression Regulation, Plant
  • Immunity, Innate / genetics
  • Molecular Sequence Data
  • Mutation
  • Plant Diseases / genetics
  • Plant Diseases / microbiology
  • Plant Proteins / genetics
  • Plasmids / genetics
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / physiology
  • Proto-Oncogene Proteins c-bcl-2*
  • Pseudomonas syringae / pathogenicity*
  • Rhizobium / genetics
  • Rhizobium / growth & development
  • Sequence Deletion
  • Signal Transduction / genetics
  • Signal Transduction / physiology
  • Tobacco / genetics
  • Tobacco / metabolism*
  • Tobacco / microbiology
  • Virulence
  • Yeasts / genetics
  • Yeasts / physiology*
  • bcl-2-Associated X Protein

Substances

  • Bacterial Proteins
  • Plant Proteins
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • avrPto protein, Pseudomonas syringae
  • bcl-2-Associated X Protein
  • pathogenesis-related proteins, plant

Associated data

  • GENBANK/AY208295
  • GENBANK/AY208296
  • GENBANK/AY208297
  • GENBANK/AY208298
  • GENBANK/AY321312