How plants regulate their water levels
An EU-funded research team has discovered how a hormone regulates the response of plants to stressful situations such as drought. The study's findings, published this week in the journal Nature, could be used in the future for increasing the resistance of plants to water shortage or drought. EU support for the work came from the PCUBE ('Infrastructure for protein production platforms') project, which is funded under the research infrastructures budget line of the Seventh Framework Programme (FP7). The internal workings of abscisic acid (ABA), the hormone in question, have not been understood previously. Now, however, scientists from the European Molecular Biology Laboratory (EMBL) at Grenoble in France, and Consejo Superior de Investigaciones Científicas (CSIC) in Valencia, Spain, have discovered that the answer lies in a protein called PYR1and how it interacts with ABA. Normally, proteins called PP2Cs regulate the flow of ABA in a plant, but when the plant experiences a stressful situation such as lack of water, the amount of ABA increases similarly to the adrenaline increase in a human being under stress. When the level of ABA rises in a plant, its cells are flooded with signals that it needs more water. This turns on or off specific genes that trigger mechanisms for remedying the situation such as increasing water uptake, storing more water or trying to conserve water as much as possible. But the ABA and the PP2C proteins do not interact with each other, so the way that proteins affect the ABA was not previously known. The research team looked at a group of 14 proteins in the structure of a plant to try to discover if they were involved in the process. One of these proteins, PYR1, was examined to discover its structure, and under X-ray crystallography it was found to resemble a hand. The X-rays showed that without the presence of ABA, the PYR1 'hand' remained open. When ABA was present, however, the 'hand' closed around it. This enabled a molecule of PP2C to 'sit' on top of the hand. Most of the group of proteins reacted in this way, thereby confirming this group of proteins as the main ABA receptors. The team found that by binding to the protein PYR1, ABA causes it to 'hijack' PP2C molecules, which then cannot block the stress response. 'If you treat the plants with ABA before a drought occurs, they take all their winter-saving measures before the drought actually hits, so they are more prepared and more likely to survive that water shortage - they become more tolerant to drought,' explained Dr Pedro Luis Rodríguez from CSIC. 'The problem so far,' added Dr José Antonio Márquez from EMBL, 'has been that ABA is very difficult - and expensive - to produce. But thanks to this structural biology approach, we now know what ABA interacts with and how, and this can help to find other molecules with the same effect but which can be feasibly produced and applied.'
Countries
Spain, France