Specific Threonine Phosphorylation of a Host Target by Two Unrelated Type III Effectors Activates a Host Innate Immune Receptor in Plants

Cell Host Microbe. 2011 Feb 17;9(2):125-36. doi: 10.1016/j.chom.2011.01.009.

Abstract

The Arabidopsis NB-LRR immune receptor RPM1 recognizes the Pseudomonas syringae type III effectors AvrB or AvrRpm1 to mount an immune response. Although neither effector is itself a kinase, AvrRpm1 and AvrB are known to target Arabidopsis RIN4, a negative regulator of basal plant defense, for phosphorylation. We show that RIN4 phosphorylation activates RPM1. RIN4(142-176) is necessary and, with appropriate localization sequences, sufficient to support effector-triggered RPM1 activation, with the threonine residue at position 166 being critical. Phosphomimic substitutions at T166 cause effector-independent RPM1 activation. RIN4 T166 is phosphorylated in vivo in the presence of AvrB or AvrRpm1. RIN4 mutants that lose interaction with AvrB cannot be coimmunoprecipitated with RPM1. This defines a common interaction platform required for RPM1 activation by phosphorylated RIN4 in response to pathogenic effectors. Conservation of an analogous threonine across all RIN4-like proteins suggests a key function for this residue beyond the regulation of RPM1.

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

  • Arabidopsis / genetics
  • Arabidopsis / immunology*
  • Arabidopsis / metabolism
  • Arabidopsis / microbiology
  • Arabidopsis Proteins / chemistry
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / immunology*
  • Arabidopsis Proteins / metabolism*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Carrier Proteins / chemistry
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Host-Pathogen Interactions
  • Intracellular Signaling Peptides and Proteins
  • Phosphorylation
  • Plant Diseases / immunology*
  • Plant Diseases / microbiology
  • Protein Binding
  • Protein Structure, Tertiary
  • Pseudomonas syringae / genetics
  • Pseudomonas syringae / metabolism*
  • Threonine / metabolism*

Substances

  • Arabidopsis Proteins
  • AvrB protein, Pseudomonas syringae
  • AvrRpm1 protein, Pseudomonas syringae
  • Bacterial Proteins
  • Carrier Proteins
  • Intracellular Signaling Peptides and Proteins
  • RIN4 protein, Arabidopsis
  • RPM1 protein, Arabidopsis
  • Threonine