Hinano Takase, Aina Nagano, Shota Yamauchi, Yuki Hayashi, Koji Takahashi, Yoshiaki Kamiyama, Kota Yamashita, Sotaro Katagiri, Yangdan Li, Saashia Fuji, Kyoka Tahara, Minoru Noguchi, Yoshiki Kawaguchi, Shunsuke Adachi, Yutaka Kodama, Ryuichi Nishihama, Atsushi Takemiya, Toshinori Kinoshita, Taishi Umezawa
The plasma membrane proton pump [PM H + -adenosine triphosphatase (PM H + -ATPase)] is essential in plants. C-terminal phosphorylation events regulate proton pump activity, such as Thr 881 phosphorylation in Arabidopsis AHA1. We discovered a sequential protein phosphorylation pathway in which two distinct types of Raf-like protein kinases, C5-Raf and C7-Raf, form a heterocomplex that phosphorylates Thr 881 to activate PM H + -ATPases. This regulatory system is highly conserved across lineages from liverworts to angiosperms. In Arabidopsis , a C5-Raf Raf36 regulates plant growth through the phosphorylation of multiple Arabidopsis H + -ATPases (AHAs). Additionally, another C5-Raf HT1 functions with C7-Rafs CBC1/2 to phosphorylate AHA1 T881 , thereby generating a driving force for light-induced stomatal opening. Our findings provide a framework for understanding PM H + -ATPase activation in various physiological processes, particularly in elucidating the complete mechanistic understanding of light-induced stomatal opening.