Figure 7.

Schematic illustrating part of SA's antagonistic effects on the ABA signaling module. (a) In the absence of ABA, free PP2Cs prevents autophosphorylation‐dependent activation of SnRK2s by dephosphorylating them. (b) In the presence of ABA, PYR/PYL receptors tightly bind to PP2Cs, thereby preventing free PP2C‐mediated dephosphorylation of SnRK2s. Receptor‐mediated occlusion of PP2Cs allows autophosphorylation‐dependent activation of SnRK2s to relay the ABA signaling by phosphorylating downstream targets such as abscisic acid‐responsive element‐binding factor 2 (ABF2), which enables its binding to ABA‐responsive elements (ABRE) in the promoter region of ABA‐responsive genes. (c) SA suppresses ABA's enhancement of the interaction of PP2Cs with the PYR/PYL/RCAR receptor and the resulting autophosphorylation‐dependent activation of SnRK2s, which results in reduced ABA signaling. The length and thickness of the arrows indicate the equilibrium between free and receptor‐bound PP2Cs and between inactive, nonphosphorylated and active, autophosphorylated SnRK2s