Abscisic acid signaling

ABA plays a crucial role for plant response to abiotic stress and regulation of plant growth and development. For instance, drought increases ABA levels and plant response to ABA is a key adaptive mechanism to resist drought stress. Thus, elucidating the ABA signaling pathway holds enormous promise for biotechnological application in agriculture. Key details of the pathway have been elucidated recently, such as the discovery of the 14-member PYR/PYL/RCAR family of ABA-receptors. These ABA-receptors inhibit in an ABA-dependent manner the clade A phosphatases type-2C (PP2Cs), which are key negative regulators of the ABA pathway. Inhibition of PP2Cs leads to activation of sucrose non-fermenting 1-related subfamily 2 (SnRK2) kinases, which regulate stomatal aperture and transcriptional response to ABA. Thus, a core signaling network for ABA has emerged from these findings and crystallographic models are available for ABA receptors, receptor-ABA-phosphatase or phosphatase-kinase complexes.