Arabidopsis E3 ligase KEG associates with and ubiquitinates MKK4 and MKK5 to regulate plant immunity  

作　　者：Chenyang Gao Pengwei Sun Wei Wang Dingzhong Tang 

机构地区：[1]State Key Laboratory of Ecological Control of Fujian-Taiwan Crop Pests,Key Laboratory of Ministry of Education for Genetics,Breeding and Multiple Utilization of Crops,Plant Immunity Center,Fujian Agriculture and Forestry University,Fuzhou 350002,China [2]Institute of Genetics and Developmental Biology,the Chinese Academy of Sciences,Beijing 100101,China [3]College of Life Sciences,University of Chinese Academy of Sciences,Beijing 100049,China

出　　处：《Journal of Integrative Plant Biology》2021年第2期327-339,共13页植物学报（英文版）

基　　金：supported by grants from the National Natural Science Foundation of China (31761133017 and 31525019) to D.T。

摘　　要：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 finetune immune responses by regulating the homeostasis of key MAPK cascade members via ubiquitination and degradation.

关 键 词：MAPK cascade plant immunity KEG EDR1 MKK4 MKK5 ARABIDOPSIS powdery mildew 

分 类 号：S432.2[农业科学—植物病理学]