The FLS2-associated kinase BIK1 directly phosphorylates the NADPH oxidase RbohD to control plant immunity

Cell Host Microbe. 2014 Mar 12;15(3):329-38. doi: 10.1016/j.chom.2014.02.009.


The Arabidopsis immune receptor FLS2 senses the bacterial flagellin epitope flg22 to activate transient elevation of cytosolic calcium ions, production of reactive oxygen species (ROS), and other signaling events to coordinate antimicrobial defenses, such as stomatal closure that limits bacterial invasion. However, how FLS2 regulates these signaling events remains largely unknown. Here we show that the receptor-like cytoplasmic kinase BIK1, a component of the FLS2 immune receptor complex, not only positively regulates flg22-triggered calcium influx but also directly phosphorylates the NADPH oxidase RbohD at specific sites in a calcium-independent manner to enhance ROS generation. Furthermore, BIK1 and RbohD form a pathway that controls stomatal movement in response to flg22, thereby restricting bacterial entry into leaf tissues. These findings highlight a direct role of the FLS2 complex in the regulation of RbohD-mediated ROS production and stomatal defense.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / immunology*
  • Arabidopsis Proteins / metabolism*
  • NADPH Oxidases / metabolism*
  • Phosphorylation
  • Protein Kinases / metabolism*
  • Protein Processing, Post-Translational*
  • Protein Serine-Threonine Kinases / metabolism*
  • Reactive Oxygen Species / metabolism


  • Arabidopsis Proteins
  • Reactive Oxygen Species
  • respiratory burst oxidase homolog D, Arabidopsis
  • NADPH Oxidases
  • Protein Kinases
  • FLS2 protein, Arabidopsis
  • BIK1 protein, Arabidopsis
  • Protein Serine-Threonine Kinases