Regulators of PP2C Phosphatase Activity Function as Abscisic Acid Sensors

ABA Receptor Rumbled? The plant hormone abscisic acid (ABA) is critical for normal development and for mediating plant responses to stressful environmental conditions. Now, two papers present analyses of candidate ABA receptors (see the news story by Pennisi ). Ma et al. (p. 1064; published online 30 April) and Park et al. (p. 1068, published online 30 April) used independent strategies to search for proteins that physically interact with ABI family phosphatase components of the ABA response signaling pathway. Both groups identified different members of the same family of proteins, which appear to interact with ABI proteins to form a heterocomplex that can act as the ABA receptor. The variety of both families suggests that the ABA receptor may not be one entity, but rather a class of closely related complexes, which may explain previous difficulties in establishing its identity.