EMBL study helps to understand drought resistance
Much as adrenaline coursing through our veins drives our body’s reactions to stress, the plant hormone abscisic acid (ABA) is behind plants’ responses to stressful situations such as drought, but how it does so has been a mystery for years. Scientists at the European Molecular Biology Laboratory (EMBL) in Grenoble, France, and the Consejo Superior de Investigaciones Cientificas (CSIC) in Valencia, Spain discovered that the key lies in the structure of a protein called PYR1 and how it interacts with the hormone. Their study, published online in Nature, could open up new approaches to increasing
crops’ resistance to water shortage (more...). Under normal conditions, a family of proteins called Type 2C phosphatases inhibit the ABA pathway. When a plant is subjected to drought, the concentration of ABA in its cells increases, removing the brake and allowing the signal for drought response to be triggered. This in turn initiates mechanisms for increasing water uptake and storage, and decreasing water loss. While it is known that ABA does not interact directly with Type 2C phosphatases, recent studies had indicated that
another family of proteins mediate between these two. Scientists led by José Antonio Márquez from EMBL Grenoble, and Pedro Luis Rodriguez from CSIC, examined one member of this third family of proteins, called PYR1. X-ray crystallography shows that PYR1 has an open structure, like an outstretched hand, in the absence of ABA. When ABA is present it sits in the ‘palm’ of the PYR1 hand, which then closes over the hormone as if holding a ball. This enables a Type 2C phosphatase to sit on top of the folded fingers. As these features seem to be conserved across most members of this protein family, this
confirms PYR1 and others in this protein family as the main ABA receptors. It also demonstrates how the process of stress response starts: by binding to PYR1, ABA causes it to inhibit PP2C molecules, which are therefore not available to block the stress response.