Maintaining Basal B-RAF Kinase Activity and ABA signaling via Single Serine Dephosphorylation and Autophosphorylation

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 PYR1/PYLs/RCARs, inhibiting A clade PP2C phosphatases and releasing SnRK2s from PP2C-mediated inhibition. 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 A clade PP2Cs interact with and dephosphorylate B3 subgroup RAFs at a conserved serine residue, corresponding to Ser619 in RAF3, within the phosphate-binding loop. A phosphomimicking mutation at this residue, RAF3S619D, failed to bind ATP and exhibited diminished kinase activity in vitro and in vivo.

INSTRUMENT(S):

ORGANISM(S): Arabidopsis Thaliana (mouse-ear Cress)

TISSUE(S): Whole Body

SUBMITTER: chen zhu  

LAB HEAD: Pengcheng Wang

PROVIDER: PXD053394 | Pride | 2025-11-10

REPOSITORIES: Pride