These include a chloroplast envelope-localized receptor (the H subunit of Chloroplast [Mg.sup.++]-chelatase/ABA Receptor), two plasma membrane-localized receptors (G-PROTEIN COUPLED RECEPTOR 2 (
GPCR2) and GPCR-type G proteins), and a cytosol/nucleus-localized receptor, named PYRABACTIN RESISTANT/PYR-LIKE/REGULATORY COMPONENT OF ABA RECEPTOR 1 (PYR/PYL/RCAR) (Guo et al., 2011).