MEKK2 inhibits activation of MAP kinases in Arabidopsis

Plant J. 2020 Jul;103(2):705-714. doi: 10.1111/tpj.14763. Epub 2020 Apr 28.

Abstract

The Arabidopsis MEKK1-MKK1/MKK2-MPK4 kinase cascade is monitored by the nucleotide-binding leucine-rich-repeat immune receptor SUMM2. Disruption of this kinase cascade leads to activation of SUMM2-mediated immune responses. MEKK2, a close paralog of MEKK1, is required for defense responses mediated by SUMM2, the molecular mechanism of which is unclear. In this study, we showed that MEKK2 serves as a negative regulator of MPK4. It binds to MPK4 to directly inhibit its phosphorylation by upstream MKKs. Activation of SUMM2-mediated defense responses induces the expression of MEKK2, which in turn blocks MPK4 phosphorylation to further amplify immune responses mediated by SUMM2. Intriguingly, MEKK2 locates in a tandem repeat consisting of MEKK1, MEKK2 and MEKK3, which was generated from a recent gene duplication event, suggesting that MEKK2 evolved from a MAPKKK to become a negative regulator of MAP kinases.

Keywords: Arabidopsis thaliana; MAP kinase; MEKK2; MPK4; SUMM2; plant immunity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / enzymology
  • Arabidopsis / immunology
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / metabolism*
  • Carrier Proteins / metabolism
  • Enzyme Activation
  • Gene Expression Regulation, Plant
  • MAP Kinase Kinase Kinase 2 / metabolism*
  • MAP Kinase Signaling System
  • Mitogen-Activated Protein Kinases / metabolism*

Substances

  • Arabidopsis Proteins
  • Carrier Proteins
  • SUMM2 protein, Arabidopsis
  • MPK11 protein, Arabidopsis
  • Mitogen-Activated Protein Kinases
  • MAP Kinase Kinase Kinase 2