The 30th International Conference on Arabidopsis Research (ICAR 2019)

393 / 2019-02-22 19:24:06

PMCK2 regulates plant innate immunity by protein phosphorylation

protein phosphorylation,flg22,plant immunity,signal transduction,BIK1

Plenary track > Biotic Stress

Receptor-like cytoplasmic kinases (RLCKs) serve as components to mediate the perception of diverse extracellular signals to downstream cytoplasmic signalling cascades. In plants, the RLCK BIK1 mediates FLS2/BAK1 signalling, but it is unclear how BIK1 activity and stability are controlled. Here, we show that the plasma membrane/cytoplasmic kinase 2 (PMCK2) is rapidly phosphorylated upon flg22 perception, which stabilizes and enables BIK1 activation by phosphorylation. pmck2 mutant exhibits compromised flg22-induced ROS burst and flg22-induced resistance to P. syringae. BIK1 stability is decreased in pmck2 before and after flg22 treatment and rescued by proteasome inhibitor MG132 treatment. Impaired flg22-induced immunity responses in pmck2 are completely restored by BIK1 transgene. Mechanistically, PMCK2 directly associates and phosphorylates BIK1. LC-MS/MS and transgenic lines show that the phosphorylation residues lie within the BIK1 kinase domain and are essential for BIK1 stability and activity. Furthermore, flg22-induced BIK1 hyper-phosphorylation is reduced in pmck2. PMCK2 phosphorylates and inactivates BIK1 phosphatase PP2C38 to enables full BIK1 activation. Notably, flg22-induced PMCK2 phosphorylation is dependent on BAK1 which promotes PMCK2 activation by phosphorylation. Thus, the study reveals that PMCK2 coordinates the transphosphorylation events in pattern recognition receptors (PRRs) complexes to maintain immunity homeostasis.