ABA signaling mediated by PYR/PYL/RCAR in plants

Abscisic acid (ABA) is a phytohormone that plays critical roles in numerous developmental stages as well as in adaptive responses to biotic and abiotic stresses. Recent breakthroughs in the field of ABA signaling have indicated that there are three major components, PYR/PYL/RCAR (an ABA receptor), type 2C protein phosphates (PP2C, a negative regulator), and SNF1-related protein kinase 2 (SnRK2, a positive regulator). Further results show that these three proteins construct a double negative regulatory system, PYR/PYL/RCAR-| PP2C-| SnRK2, to regulate ABA signal responses in plant cells. Moreover, the combination patterns of these components in vivo are restricted by spatio-temporal and biochemical determinants and the combinational variation in the ABA signalosome is specific to different ABA signal responses. This review summarizes recent advances of study on the molecular basis and regulatory mechanism of PYR/PYL/RCAR-mediated ABA signaling pathway and PYR/PYL/RCAR-PP2C-SnRK2 complex-mediated ABA signal regulation network in plants. The perspectives related to this study are proposed.