CASEIN KINASE1-LIKE PROTEIN2 Regulates Actin Filament Stability and Stomatal Closure via Phosphorylation of Actin Depolymerizing Factor.
The opening and closing of stomata are crucial for plant photosynthesis and transpiration. Actin filaments undergo dynamic reorganization during stomatal closure, but the underlying mechanism for this cytoskeletal reorganization remains largely unclear. In this study, we identified and characterized Arabidopsis thaliana casein kinase 1-like protein 2 (CKL2), which responds to abscisic acid (ABA) treatment and participates in ABA- and drought-induced stomatal closure. Although CKL2 does not bind to actin filaments directly and has no effect on actin assembly in vitro, it colocalizes with and stabilizes actin filaments in guard cells. Further investigation revealed that CKL2 physically interacts with and phosphorylates actin depolymerizing factor 4 (ADF4) and inhibits its activity in actin filament disassembly. During ABA-induced stomatal closure, deletion of CKL2 in Arabidopsis alters actin reorganization in stomata and renders stomatal closure less sensitive to ABA, whereas deletion of ADF4 impairs the disassembly of actin filaments and causes stomatal closure to be more sensitive to ABA Deletion of ADF4 in the ckl2 mutant partially recues its ABA-insensitive stomatal closure phenotype. Moreover, Arabidopsis ADFs from subclass I are targets of CKL2 in vitro. Thus, our results suggest that CKL2 regulates actin filament reorganization and stomatal closure mainly through phosphorylation of ADF.
Key Laboratory of Plant Stress, Life Science College, Shandong Normal University, Jinan 250014, China State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
Shuangshuang
S
Zhao
Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Science, Beijing 100093, China.
Yuxiang
Y
Jiang
State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
Yang
Y
Zhao
Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Science, Beijing 100093, China Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China.
Shanjin
S
Huang
State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
Ming
M
Yuan
Key Laboratory of Plant Stress, Life Science College, Shandong Normal University, Jinan 250014, China guoyan@cau.edu.cn zhaoyx@sdnu.edu.cn.
Yanxiu
Y
Zhao
State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China guoyan@cau.edu.cn zhaoyx@sdnu.edu.cn.
Yan
Y
Guo
D000040:Abscisic Acid / Q000494:pharmacology; D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism*; D051339:Actin Depolymerizing Factors / Q000235:genetics / Q000378:metabolism; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D055864:Droughts; D010766:Phosphorylation / Q000187:drug effects / Q000235:genetics; D054046:Plant Stomata / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics
C542432:ADF4 protein, Arabidopsis; D051339:Actin Depolymerizing Factors; D029681:Arabidopsis Proteins; D000040:Abscisic Acid