Arabidopsis heterotrimeric G proteins regulate immunity by directly coupling to the FLS2 receptor

Elife. 2016 Apr 4;5:e13568. doi: 10.7554/eLife.13568.


The Arabidopsis immune receptor FLS2 perceives bacterial flagellin epitope flg22 to activate defenses through the central cytoplasmic kinase BIK1. The heterotrimeric G proteins composed of the non-canonical Gα protein XLG2, the Gβ protein AGB1, and the Gγ proteins AGG1 and AGG2 are required for FLS2-mediated immune responses through an unknown mechanism. Here we show that in the pre-activation state, XLG2 directly interacts with FLS2 and BIK1, and it functions together with AGB1 and AGG1/2 to attenuate proteasome-mediated degradation of BIK1, allowing optimum immune activation. Following the activation by flg22, XLG2 dissociates from AGB1 and is phosphorylated by BIK1 in the N terminus. The phosphorylated XLG2 enhances the production of reactive oxygen species (ROS) likely by modulating the NADPH oxidase RbohD. The study demonstrates that the G proteins are directly coupled to the FLS2 receptor complex and regulate immune signaling through both pre-activation and post-activation mechanisms.

Keywords: a. thaliana; cell biology; heterotrimeric G proteins; oxidative burst; phosphorylation; plant biology; plant immunity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, Bacterial / immunology
  • Arabidopsis / immunology*
  • Arabidopsis Proteins / metabolism*
  • Flagellin / immunology
  • Heterotrimeric GTP-Binding Proteins / metabolism*
  • Protein Binding
  • Protein Kinases / metabolism*
  • Reactive Oxygen Species / metabolism
  • Signal Transduction


  • Antigens, Bacterial
  • Arabidopsis Proteins
  • Reactive Oxygen Species
  • Flagellin
  • Protein Kinases
  • FLS2 protein, Arabidopsis
  • Heterotrimeric GTP-Binding Proteins

Grant support

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.