Arabidopsis E3 ligase KEG associates with and ubiquitinates MKK4 and MKK5 to regulate plant immunity. Issue 2 (30th September 2020)

• Record Type: Journal Article
• Authors: Gao, Chenyang; Sun, Pengwei; Wang, Wei; Tang, Dingzhong
• Other Names: Dong Suomeng guestEditor.; Lozano‐Duran Rosa guestEditor.
• Is Part Of: Journal of integrative plant biology. Volume 63:Issue 2(2021)
• Page Start: 327
• Page End: 339
• Publication Date: 2020-09-30
• Subjects: MAPK cascade -- plant immunity -- KEG -- EDR1 -- MKK4 -- MKK5 -- Arabidopsis -- powdery mildew; Plants -- Periodicals; Plants -- China -- Periodicals; Electronic journals; 580.5
• DOI: 10.1111/jipb.13007
• Languages: English
• ISSNs: 1672-9072

Abstract

Abstract: Mitogen‐activated protein kinase (MAPK) cascades are highly conserved signaling modules that regulate plant immune responses. The Arabidopsis thaliana Raf‐like MAPK kinase kinase ENHANCED DISEASE RESISTANCE1 (EDR1) is a key negative regulator of plant immunity that affects the protein levels of MKK4 and MKK5, two important MAPK cascade members, but the underlying mechanism is poorly understood. Here, genome‐wide phosphorylation analysis demonstrated that the E3 ligase KEEP ON GOING (KEG) is phosphorylated in the edr1 mutant but not the wild type, suggesting that EDR1 negatively affects KEG phosphorylation. The identified phosphorylation sites in KEG appear to be important for its accumulation. The keg‐4 mutant, a previously identified edr1 suppressor, enhances susceptibility to the powdery mildew pathogen Golovinomyces cichoracearum . In addition, MKK4 and MKK5 protein levels are reduced in the keg‐4 mutant. Furthermore, we demonstrate that MKK4 and MKK5 associate with full‐length KEG, but not with truncated KEG‐RK or KEG‐RKA, and that KEG ubiquitinates and mediates the degradation of MKK4 and MKK5. Taken together, these results indicate that MKK4 and MKK5 protein levels are regulated by KEG via ubiquitination, uncovering a mechanism by which plants fine‐tune immune responses by regulating the homeostasis of key MAPK cascade members via ubiquitination and degradation. Abstract : The regulation of MAPK signaling is essential for plant growth, development and defense. The E3 ligase KEEP ON GOING (KEG) negatively regulates MKK4/MKK5 accumulation via ubiquitination, thus playing a crucial role in defense responses in the enhanced disease resistance1 mutant.