Structural insights into PYR/PYL/RCAR ABA receptors and PP2Cs

Abscisic acid (ABA) plays an essential function in plant physiology since it is required for biotic and abiotic stress responses as well as control of plant growth and development. A new family of soluble ABA receptors, named PYR/PYL/RCAR, has emerged as ABA sensors able to inhibit the activity of specific protein phosphatases type-2C (PP2Cs) in an ABA-dependent manner. The structural and functional mechanism by which ABA is perceived by these receptors and consequently leads to inhibition of the PP2Cs has been recently elucidated. The module PYR/PYL/RCAR-ABA-PP2C offers an elegant and unprecedented mechanism to control phosphorylation signaling cascades in a ligand-dependent manner. The knowledge of their three-dimensional structures paves the way to the design of ABA agonists able to modulate the plant stress response.

Research highlights▶ Plants have a family of 14 intracellular ABA receptors, named PYR/PYL/RCAR. ▶ These receptors are able to inhibit the activity of clade A PP2Cs in an ABA-dependent manner. ▶ The structures of three receptors, PYR1, PYL1 and PYL2, and two receptor-ABA-phosphatase complexes, PYL1-ABI1 and PYL2-HAB1, have been elucidated. ▶ The gain-of-function mutations abi1G180D, abi2G168D and hab1G246D are immune to receptor-mediated inhibition.