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Raf-like protein kinase heterocomplexes directly regulate the plant plasma membrane H+-ATPase
Hinano Takase1, Aina Nagano1, Shota Yamauchi2
1Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Tokyo, Japan.
Science (New York, N.Y.)
|May 14, 2026
Summary
Plant plasma membrane proton pumps are activated by a sequential phosphorylation pathway involving C5-Raf and C7-Raf kinases. This conserved mechanism regulates growth and light-induced stomatal opening.
Area of Science:
- Plant Biology
- Molecular Plant Physiology
- Biochemistry
Background:
- Plasma membrane proton pumps (PM H+-ATPases) are crucial for plant cell function.
- C-terminal phosphorylation, specifically at Thr881 in Arabidopsis AHA1, regulates PM H+-ATPase activity.
Purpose of the Study:
- To elucidate the sequential protein phosphorylation pathway regulating PM H+-ATPase activation.
- To identify the protein kinases involved in Thr881 phosphorylation.
- To understand the physiological roles of this regulatory system in plant growth and stomatal opening.
Main Methods:
- Investigated protein kinase interactions and phosphorylation events.
- Utilized genetic and biochemical approaches in Arabidopsis.
- Examined the role of Raf-like kinases in regulating PM H+-ATPases.
Main Results:
- Discovered a heterocomplex of C5-Raf and C7-Raf kinases that phosphorylates Thr881 to activate PM H+-ATPases.
- Identified Raf36 (C5-Raf) as a regulator of plant growth via AHA phosphorylation.
- Demonstrated that HT1 (C5-Raf) and CBC1/2 (C7-Raf) phosphorylate AHA1T881, driving light-induced stomatal opening.
Conclusions:
- A conserved sequential phosphorylation pathway activates plant PM H+-ATPases.
- This system is vital for regulating plant growth and physiological responses like stomatal opening.
- Provides a mechanistic framework for PM H+-ATPase activation in diverse plant processes.
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