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

Yashitola Jamir, Ming Guo, Hye Sook Oh, Tanja Petnicki-Ocwieja, Shaorong Chen, Xiaoyang Tang, Martin B. Dickman, Alan Collmer, James R. Alfano

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207 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)554-565
Number of pages12
JournalPlant Journal
Issue number4
StatePublished - Feb 1 2004



  • Avr proteins
  • Bacterial plant pathogens
  • Innate immunity
  • Plant defense
  • Programmed cell death
  • Type III effectors

ASJC Scopus subject areas

  • Genetics
  • Plant Science
  • Cell Biology

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