Arabidopsis group C Raf-like protein kinases negatively regulate abscisic acid signaling and are direct substrates of SnRK2

Yoshiaki Kamiyama, Misaki Hirotani, Shinnosuke Ishikawa, Fuko Minegishi, Sotaro Katagiri, Conner J. Rogan, Fuminori Takahashi, Mika Nomoto, Kazuya Ishikawa, Yutaka Kodama, Yasuomi Tada, Daisuke Takezawa, Jeffrey C. Anderson, Scott C. Peck, Kazuo Shinozaki, Taishi Umezawa

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17 Citations (Scopus)


The phytohormone abscisic acid (ABA) plays a major role in abiotic stress responses in plants, and subclass III SNF1-related protein kinase 2 (SnRK2) kinases mediate ABA signaling. In this study, we identified Raf36, a group C Raf-like protein kinase in Arabidopsis, as a protein that interacts with multiple SnRK2s. A series of reverse genetic and biochemical analyses revealed that 1) Raf36 negatively regulates ABA responses during postgermination growth, 2) the N terminus of Raf36 is directly phosphorylated by SnRK2s, and 3) Raf36 degradation is enhanced in response to ABA. In addition, Raf22, another C-type Raf-like kinase, functions partially redundantly with Raf36 to regulate ABA responses. A comparative phosphoproteomic analysis of ABA-induced responses of wild-type and raf22raf36-1 plants identified proteins that are phosphorylated downstream of Raf36 and Raf22 in planta. Together, these results support a model in which Raf36/Raf22 function mainly under optimal conditions to suppress ABA responses, whereas in response to ABA, the SnRK2 module promotes Raf36 degradation as a means of alleviating Raf36-dependent inhibition and allowing for heightened ABA signaling to occur.

Original languageEnglish
Article numbere2100073118
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number30
Publication statusPublished - Jul 27 2021
Externally publishedYes


  • Abscisic acid
  • Arabidopsis thaliana
  • Raf-like kinase
  • SnRK2

ASJC Scopus subject areas

  • General


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