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BPH1 negatively regulates ABA signaling via AtSAP9 degradation
Og-Geum Woo1, Arim Kim1, Dong Hye Seo2,3,4
1Department of Biology Education, Pusan National University, Busan, 46241, Korea.
Plant Molecular Biology
|October 20, 2025
Summary
BPH1 represses abscisic acid (ABA) signaling by targeting AtSAP9 for degradation. This study identifies BPH1 as a CRL3 substrate receptor that degrades AtSAP9, a positive regulator of ABA responses, via the ubiquitin-proteasome system.
Area of Science:
- Plant molecular biology
- Plant hormone signaling
- Abscisic acid (ABA) pathway
Background:
- BPH1 is known to repress abscisic acid (ABA)-mediated cellular responses.
- Understanding the precise mechanism of BPH1 action in ABA signaling is crucial.
Purpose of the Study:
- To investigate the binding partners of BPH1 to elucidate its mechanism in ABA signaling.
- To identify and characterize the interaction between BPH1 and Arabidopsis stress-associated protein 9 (AtSAP9).
Main Methods:
- Yeast two-hybrid and bimolecular fluorescence complementation (BiFC) assays to confirm protein interaction.
- Cell-free degradation assays and in planta experiments to assess protein stability.
- Ubiquitin-proteasome system analysis.
Main Results:
- Arabidopsis stress-associated protein 9 (AtSAP9), a positive regulator of ABA signaling, was identified as a BPH1-binding protein.
- BPH1 directly interacts with AtSAP9, leading to decreased AtSAP9 protein stability.
- BPH1 promotes the degradation of AtSAP9 via the ubiquitin-proteasome system, thereby repressing ABA signaling.
Conclusions:
- BPH1 functions as a repressor of ABA signaling by targeting AtSAP9 for degradation.
- This repression is mediated through the ubiquitin-proteasome system, highlighting a novel regulatory mechanism in ABA signaling.
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