Structural Basis of ABA Perception by PYR/PYL/RCAR Receptors - Abscisic Acid: Metabolism, Transport and Signaling - page 113

Chapter 7
Structural Basis of ABA Perception by
PYR/PYL/RCAR Receptors

Lun Jiang, Xingliang Zhang and Zhongzhou Chen

Abstract Abscisic acid (ABA) has been found to play an important role in the
adaptive responses to the abiotic and biotic stresses, such as drought and high
salinity, as well as the regulation of plant development, such as seed germina-
tion. Recent studies have identified several ABA receptors, including chloro-
plast envelope-localized receptor (the H subunit of chloroplast Mg 2 + -chelatase),
three plasma membrane-localized receptors (G protein-coupled receptor 2 and
two GPCR-type G proteins), and cytosol/nucleus-localized pyrabactin resistant-
like (PYLs) (or named regulatory component of ABA receptor (RCAR)), among
which PYLs are mostly known and confirmed by many groups. In the ABA
signaling pathway, PYLs change their conformations upon binding to the ABA
molecule, and then directly bind to and inhibit the downstream A-group protein
phosphatases 2C (PP2Cs). PYLs/PP2Cs heterodimer blocks substrates binding to
PP2Cs, and thus releases the downstream transcription factors sucrose-non-fer-
mentation kinase subfamily 2 (SnRK2s) whose kinase activity is formerly inhib-
ited by PP2Cs through physical interaction and dephosphorylation, finally allows
the plants to adapt to the stress conditions. This chapter will focus on the struc-
tural basis of ABA perception by PYR/PYL/RCAR receptors, elucidate its molec-
ular mechanisms and provide some structural details for further design of ABA
analogues.

Keywords PYR/PYL/RCAR receptors · Crystal structures · Ternary complexes ·
Chemical regulation