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The RCAR12-CAP1-OST1 module controls ABA-mediated stomatal closure in Arabidopsis
Xiaoyi Li1, Qian Zhang1, Jiangjie Kang1
1Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, China.
Plos Genetics
|April 28, 2026
Summary
Cyclase-associated protein 1 (CAP1) regulates plant drought responses. ABA signaling disrupts CAP1 interactions, leading to actin stabilization and stomatal closure, crucial for drought tolerance in Arabidopsis.
Area of Science:
- Plant Biology
- Molecular Biology
- Biochemistry
Background:
- Phytohormone abscisic acid (ABA) is vital for plant drought stress responses, notably inducing stomatal closure.
- Stomatal closure requires significant actin cytoskeleton reorganization, but the link between ABA perception and cytoskeletal dynamics is not fully understood.
Purpose of the Study:
- To investigate the role of Arabidopsis cyclase-associated protein 1 (CAP1) in ABA-induced stomatal closure and drought responses.
- To elucidate the molecular mechanisms by which CAP1 modulates the actin cytoskeleton during ABA signaling.
Main Methods:
- Yeast two-hybrid assays and co-immunoprecipitation to study protein interactions.
- Actin filament depolymerization assays to assess CAP1 activity.
- Phosphorylation assays and in vitro binding assays to analyze OST1-mediated phosphorylation of CAP1.
- Analysis of stomatal aperture in response to ABA treatment.
Main Results:
- Arabidopsis CAP1 acts as a negative regulator in ABA-induced drought responses by modulating actin network organization.
- CAP1 interacts with RCAR12, suppressing actin filament disassembly; ABA disrupts this interaction, restoring CAP1's depolymerization activity.
- ABA-activated OPEN STOMATA 1 (OST1) phosphorylates CAP1, weakening its interaction with ADF4 and inhibiting the ADF4-CAP1 complex, leading to F-actin stabilization and stomatal closure.
Conclusions:
- CAP1 orchestrates ABA-induced stomatal closure under drought stress in Arabidopsis.
- CAP1 serves as a key molecular link, coupling ABA signaling pathways to the dynamic reorganization of the actin cytoskeleton for drought adaptation.
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