Maintaining basal B‐RAF kinase activity for abscisic acid signaling via reciprocal phosphoregulation of a single serine residue
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ABSTRACT The phytohormone abscisic acid (ABA) regulates plant responses to environmental stresses, development, and immunity. Under unfavorable conditions, ABA forms a complex with its receptor proteins Pyrabactin Resistance 1 (PYR1)/PYR1‐likes (PYLs)/Regulatory Component of ABA Receptors (RCARs), inhibiting Clade A Protein Phosphatases Type 2C (PP2Cs) and releasing Sucrose Non‐Fermenting‐1‐Related Protein Kinase 2s (SnRK2s) from PP2C‐mediated inhibition. Rapidly Accelerated Fibrosarcoma (RAF) kinases from the B1, B2, and B3 subgroups phosphorylate and reactivate SnRK2s, initiating ABA responses. While ABA does not significantly activate B‐RAFs, their basal activity is essential for initiating ABA signaling. However, the mechanisms sustaining this basal B‐RAF activity are not fully understood. In this study, we revealed that Clade A PP2Cs interact with and dephosphorylate a certain number of B3 subgroup RAFs at a conserved serine residue, corresponding to Ser619 in RAF3, within the phosphate‐binding loop. A phosphomimicking mutation at this residue, RAF3 S619D , failed to bind ATP and exhibited diminished kinase activity in vitro and in vivo . Ser619 in RAF3 is an autophosphorylation site, phosphorylated by recombinant RAF3‐KD but not by its substrate SnRK2.6. The RAF3 S619A mutant, abolishing Ser619 autophosphorylation, displayed increased kinase activity in vitro . The B‐RAF high‐order mutant OK 100 ‐B3 carrying RAF3 S619A showed enhanced ABA sensitivity compared with those with wild‐type RAF3. Thus, PP2C‐mediated dephosphorylation and the autophosphorylation of this unique serine residue dynamically regulate ATP binding affinity and tightly control RAF3 activity during various ABA signaling phases. This intricate mechanism ensures rapid RAF–SnRK2 cascade activation during stress while promptly desensitizing RAFs once stress signaling commences.
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Le contrôle bibliographique ouvert
DOI retrouvé dans Crossref DOI retrouvé ; titre concordant.
- Titre Crossref
- Maintaining basal B‐RAF kinase activity for abscisic acid signaling via reciprocal phosphoregulation of a single serine residue
- Date Crossref
- 08/08/2025
- Éditeur
- Wiley
- Type
- journal-article
Ce recoupement confirme des métadonnées liées au DOI. Il ne confirme ni la méthode ni les conclusions de l’étude, et il ne compte pas comme une seconde source scientifique indépendante.
Où se fait cette recherche
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Chinese Academy of Sciences Shanghai Center for Plant Stress Biology pays non établi dans la noticeOrganisme public
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Southern University of Science and Technology Institute of Advanced Biotechnology pays non établi dans la noticeUniversité ou école supérieure
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Center for Excellence in Molecular Plant Sciences pays non établi dans la noticeUniversité ou école supérieure
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University of Chinese Academy of Sciences pays non établi dans la noticeUniversité ou école supérieure
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Henan University Key Laboratory of Plant Stress Biology pays non établi dans la noticeUniversité ou école supérieure
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and School of Medicine Institute of Advanced Biotechnology pays non établi dans la noticeUniversité ou école supérieure
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These authors contributed equally to this article pays non établi dans la noticeInstitution
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School of Life Sciences Key Laboratory of Plant Stress Biology pays non établi dans la noticeUniversité ou école supérieure
Shanghai Center for Plant Stress Biology — Chinese Academy of Sciences, Institute of Advanced Biotechnology — Southern University of Science and Technology et Center for Excellence in Molecular Plant Sciences, avec 5 autres affiliations.
Une affiliation ne permet pas de déduire la nationalité d’un auteur.