A bacterial E3 ubiquitin ligase targets a host protein kinase to disrupt plant immunity

Nature. 2007 Jul 19;448(7151):370-4. doi: 10.1038/nature05966.

Abstract

Many bacterial pathogens of plants and animals use a type III secretion system to deliver diverse virulence-associated 'effector' proteins into the host cell. The mechanisms by which these effectors act are mostly unknown; however, they often promote disease by suppressing host immunity. One type III effector, AvrPtoB, expressed by the plant pathogen Pseudomonas syringae pv. tomato, has a carboxy-terminal domain that is an E3 ubiquitin ligase. Deletion of this domain allows an amino-terminal region of AvrPtoB (AvrPtoB(1-387)) to be detected by certain tomato varieties leading to immunity-associated programmed cell death. Here we show that a host kinase, Fen, physically interacts with AvrPtoB(1-387 )and is responsible for activating the plant immune response. The AvrPtoB E3 ligase specifically ubiquitinates Fen and promotes its degradation in a proteasome-dependent manner. This degradation leads to disease susceptibility in Fen-expressing tomato lines. Various wild species of tomato were found to exhibit immunity in response to AvrPtoB(1-387 )and not to full-length AvrPtoB. Thus, by acquiring an E3 ligase domain, AvrPtoB has thwarted a highly conserved host resistance mechanism.

Publication types

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

MeSH terms

  • Phenotype
  • Plant Diseases / immunology*
  • Plant Diseases / microbiology
  • Proteasome Endopeptidase Complex / metabolism
  • Protein Binding
  • Protein Kinases / metabolism*
  • Pseudomonas syringae / enzymology*
  • Pseudomonas syringae / immunology
  • Solanum lycopersicum / classification
  • Solanum lycopersicum / enzymology
  • Solanum lycopersicum / immunology*
  • Solanum lycopersicum / microbiology*
  • Ubiquitin / metabolism*
  • Ubiquitin-Protein Ligases / chemistry
  • Ubiquitin-Protein Ligases / metabolism*

Substances

  • Ubiquitin
  • Ubiquitin-Protein Ligases
  • Protein Kinases
  • Proteasome Endopeptidase Complex