MEKK2 inhibits activation of MAP kinases in Arabidopsis. (28th April 2020)

• Record Type: Journal Article
• Authors: Nitta, Yukino; Qiu, Yichun; Yaghmaiean, Hoda; Zhang, Qian; Huang, Jianhua; Adams, Keith; Zhang, Yuelin
• Is Part Of: Plant journal. Volume 103:Number 2(2020)
• Page Start: 705
• Page End: 714
• Publication Date: 2020-04-28
• Subjects: Arabidopsis thaliana -- MAP kinase -- MEKK2 -- MPK4 -- plant immunity -- SUMM2; Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.14763
• Languages: English
• ISSNs: 0960-7412

Abstract

SUMMARY: 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. Significance Statement: Arabidopsis MEKK2 amplifies the defense response mediated by the plant immune receptor SUMM2 through inhibition of MAP kinase activation. MEKK2 evolved from a recent gene duplication event at the MEKK1 locus followed by a striking function divergence.