Structure of Ligand-Bound Intermediates of Crop ABA Receptors Highlights PP2C as Necessary ABA Co-receptor

Dear Editor Abscisic acid （ABA） is the main phytohormone involved in adaptive crop responses to drought. ABA signaling relies on the family of pyrabactin resistance 1/PYRl-like/regulatory components of ABA receptors （PYR/PYL/RCAR）, which upon ABA binding form high-affinity ternary complexes with clade A protein phosphatases type 2C （PP2Cs） and inhibit them （Cutler et al., 2010）. This results in the activation of an SnRK2-dependent phosphorylation cascade affecting a high number of targets in the plant cells, regulating stomatal aper- ture and the expression of stress-responsive genes （Cutler et al., 2010）.