Fig. 7: A model illustrating the role of B2 and B3 RAFs in ABA signaling in Arabidopsis.
From: Initiation and amplification of SnRK2 activation in abscisic acid signaling
Under unstressed conditions, PP2C binds to and inhibits SnRK2 protein to prevent the transphosphorylation by activated RAFs (left panel). In the presence of ABA, ABA receptor PYR/PYL/RCARs (PYL) complex binds to and inhibits PP2C and SnRK2 is released from PP2C-mediated inhibition. SnRK2 can then be quickly activated by RAFs. In the meantime, stress also activates RAFs by an unknown mechanism (middle panel). The activated SnRK2 can quickly trans-phosphorylate more SnRK2 proteins to amplify the activation and phosphorylate downstream substrates to mediate stress responses (right panel).
