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

Tracy R. Rosebrock, Lirong Zeng, Jennifer J. Brady, Robert B. Abramovitch, Fangming Xiao, Gregory B. Martin

Research output: Contribution to journalArticlepeer-review

256 Scopus citations


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 (AvrPtoB1-387) 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 AvrPtoB1-387and 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 AvrPtoB1-387and not to full-length AvrPtoB. Thus, by acquiring an E3 ligase domain, AvrPtoB has thwarted a highly conserved host resistance mechanism.

Original languageEnglish (US)
Pages (from-to)370-374
Number of pages5
Issue number7151
StatePublished - Jul 19 2007
Externally publishedYes

ASJC Scopus subject areas

  • General


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