Mol Plant , IF:12.084 , 2019 Jan , V12 (1) : P59-70 doi: 10.1016/j.molp.2018.10.008
RECEPTOR-LIKE KINASE 902 Associates with and Phosphorylates BRASSINOSTEROID-SIGNALING KINASE1 to Regulate Plant Immunity.
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, Fujian 350002, China; University of Chinese Academy of Sciences, Beijing 100039, China; Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.; Provincial Key Laboratory of Eco-Industrial Green Technology, College of Ecology and Resources Engineering, Wuyi University, Wuyishan, Fujian 354300, China.; 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, Fujian 350002, China; Fujian Key Laboratory of Crop by Design, Fujian Agriculture and Forestry University, Fuzhou 350002, China.; 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, Fujian 350002, China; Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China. Electronic address: dztang@genetics.ac.cn.
Plants employ receptor-like kinases (RLKs) and receptor-like proteins for rapid recognition of invading pathogens, and RLKs then transmit signals to receptor-like cytoplasmic kinases (RLCKs) to activate immune responses. RLKs are under fine regulation mediated by subcellular trafficking, which contributes to proper activation of plant immunity. In this study, we show that Arabidopsis thaliana RECEPTOR-LIKE KINASE 902 (RLK902) plays important roles in resistance to the bacterial pathogen Pseudomonas syringae, but not to the fungal powdery mildew pathogen Golovinomyces cichoracearum. RLK902 localizes at the plasma membrane and associates with ENHANCED DISEASE RESISTANCE 4 (EDR4), a protein involved in clathrin-mediated trafficking pathways. EDR4 and CLATHRIN HEAVY CHAIN 2 (CHC2) regulate the subcellular trafficking and accumulation of RLK902 protein. Furthermore, we found that RLK902 directly associates with the RLCK BRASSINOSTEROID-SIGNALING KINASE1 (BSK1), a key component of plant immunity, but not with other members of the FLAGELLIN SENSING 2 immune complex. RLK902 phosphorylates BSK1, and its Ser-230 is a key phosphorylation site critical for RLK902-mediated defense signaling. Taken together, our data indicate that EDR4 regulates plant immunity by modulating the subcellular trafficking and protein accumulation of RLK902, and that RLK902 transmits immune signals by phosphorylating BSK1.
PMID: 30408577
New Phytol , IF:8.512 , 2019 Jan , V221 (2) : P908-918 doi: 10.1111/nph.15437
BES1 hinders ABSCISIC ACID INSENSITIVE5 and promotes seed germination in Arabidopsis.
State Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing, 100193, China.
Proper regulation of seed germination is essential for the successful propagation of a plant. The transcription factor ABSCISIC ACID INSENSITIVE5 (ABI5) of the abscisic acid (ABA) signaling pathway plays a central role in the inhibition of seed germination. ABI5 is precisely regulated by the core ABA signaling components and multiple other factors. However, the complex regulatory network of ABI5 remains largely unknown. In this study, we determined the biochemical interaction between ABI5 and the BRINSENSITIVE1 (BRI1)-EMS-SUPPRESSOR1 (BES1) transcription factor of the brassinosteroid (BR) signaling pathway, as well as the function of BES1 regulating ABI5 during seed germination in Arabidopsis. BES1 directly interacts with ABI5 both in vitro and in vivo. The bZIP domain of ABI5, which is responsible for DNA binding, is critical for ABI5 binding to BES1. The interaction of BES1 with ABI5 significantly suppressed the binding of ABI5 to the promoter regions of downstream genes, which resulted in their reduced expression and consequently facilitated seed germination. This study shed new light on the coordination of multiple signaling pathways during seed germination. In particular, BES1 directly binds to ABI5, which interferes with its transcriptional activity and suppresses ABA signaling output.
PMID: 30230549
PLoS Genet , IF:5.174 , 2019 Jan , V15 (1) : Pe1007904 doi: 10.1371/journal.pgen.1007904
BRASSINOSTEROID-SIGNALING KINASE 3, a plasma membrane-associated scaffold protein involved in early brassinosteroid signaling.
Howard Hughes Medical Institute, Salk Institute for Biological Studies, La Jolla, California, United States of America.; Plant Biology Laboratory, Salk Institute for Biological Studies, La Jolla, California, United States of America.; Department of Plant and Microbial Biology, University of Minnesota, Saint Paul, Minnesota, United States of America.; Laboratoire Reproduction et Developpement des Plantes, Universite de Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRA, Lyon, France.; Donald Danforth Plant Science Center, Saint Louis, Missouri, United States of America.
Brassinosteroids (BRs) are steroid hormones essential for plant growth and development. The BR signaling pathway has been studied in some detail, however, the functions of the BRASSINOSTEROID-SIGNALING KINASE (BSK) family proteins in the pathway have remained elusive. Through forward genetics, we identified five semi-dominant mutations in the BSK3 gene causing BSK3 loss-of-function and decreased BR responses. We therefore investigated the function of BSK3, a receptor-like cytoplasmic kinase, in BR signaling and plant growth and development. We find that BSK3 is anchored to the plasma membrane via N-myristoylation, which is required for its function in BR signaling. The N-terminal kinase domain is crucial for BSK3 function, and the C-terminal three tandem TPR motifs contribute to BSK3/BSK3 homodimer and BSK3/BSK1 heterodimer formation. Interestingly, the effects of BSK3 on BR responses are dose-dependent, depending on its protein levels. Our genetic studies indicate that kinase dead BSK3K86R protein partially rescues the bsk3-1 mutant phenotypes. BSK3 directly interacts with the BSK family proteins (BSK3 and BSK1), BRI1 receptor kinase, BSU1 phosphatase, and BIN2 kinase. BIN2 phosphorylation of BSK3 enhances BSK3/BSK3 homodimer and BSK3/BSK1 heterodimer formation, BSK3/BRI1 interaction, and BSK3/BSU1 interaction. Furthermore, we find that BSK3 upregulates BSU1 transcript and protein levels to activate BR signaling. BSK3 is broadly expressed and plays an important role in BR-mediated root growth, shoot growth, and organ separation. Together, our findings suggest that BSK3 may function as a scaffold protein to regulate BR signaling. The results of our studies provide new insights into early BR signaling mechanisms.
PMID: 30615605