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The CPK8-AHA1 phosphorylation module dampens plasma membrane H+-ATPase activity to confer drought tolerance
Xiao Liu1, Dongmin Zhang1, Yongqing Yang1
1State Key Laboratory of Plant Environmental Resilience (SKLPER), College of Biological Sciences, China Agricultural University, Beijing 100193, China.
Plant Physiology
|March 7, 2026
Summary
Plant drought tolerance is enhanced by CALCIUM-DEPENDENT KINASE 8 (CPK8) phosphorylating the plasma membrane proton (H+)-ATPase. This mechanism fine-tunes stomatal closure, reducing water loss during drought stress.
Area of Science:
- Plant Physiology
- Molecular Biology
- Biochemistry
Background:
- Plasma membrane (PM) proton (H+)-ATPase regulates plant growth and stress responses.
- PM H+-ATPase inhibition promotes stomatal closure, reducing water loss in drought conditions.
- The mechanism by which calcium (Ca2+) signals modulate PM H+-ATPase activity is not fully understood.
Purpose of the Study:
- To elucidate the mechanism by which Ca2+ signals regulate PM H+-ATPase activity.
- To identify the specific kinase involved in modulating PM H+-ATPase activity.
- To investigate the role of this regulatory pathway in plant drought tolerance.
Main Methods:
- Co-immunoprecipitation assays to confirm physical interaction between CPK8 and AHA1.
- In vitro kinase assays to determine the phosphorylation site and effect on AHA1 activity.
- Analysis of plant phenotypes (transpirational water loss, leaf temperature) in CPK8 overexpression and ost2-2D mutant lines under drought stress.
- Monitoring Ca2+ signals and CPK8 activation during drought stress.
Main Results:
- Arabidopsis CALCIUM-DEPENDENT KINASE 8 (CPK8) physically interacts with and phosphorylates PLASMA MEMBRANE PROTON ATPASE 1 (AHA1) at Ser-899.
- CPK8-mediated phosphorylation significantly inhibits AHA1 H+-ATPase activity.
- CPK8 overexpression ameliorated excessive water loss in ost2-2D mutants and increased leaf temperature.
- Drought-induced Ca2+ signals activate CPK8, modulating PM H+-ATPase activity.
Conclusions:
- CPK8 acts as a key regulator of PM H+-ATPase activity through phosphorylation.
- This CPK8-AHA1 pathway is crucial for fine-tuning stomatal closure in response to drought stress.
- The findings reveal a novel mechanism for optimizing plant drought tolerance.
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