How plants survive droughts

A team of biologists in California led by researchers at The Scripps Research Institute and the University of California (UC), San Diego, has solved the structure of a critical molecule that helps plants survive during droughts.

Understanding the inner workings of this molecule may help scientists design new ways to protect crops against prolonged dry periods, potentially improving crop yields worldwide, aiding biofuels production on marginal lands and mitigating drought's human and economic costs.

"This molecular structure helps explain the mechanism behind drought tolerance in plants," said Elizabeth Getzoff, a Scripps Research scientist who led the team from Scripps Research, UC San Diego, Lawrence Berkeley National Laboratory, and UC Riverside.

The newly solved structure shows a three-dimensional representation of a critical plant hormone called abscisic acid, attached to its "target" protein called PYR1.

Abscisic acid is key to many plant processes, including to survival tactics in challenging environmental conditions.

"In revealing how a plant hormone functions under stressful conditions, this work provides important clues about how hormones might regulate crucial physiological responses in humans," said Jean Chin, a program director with the National Institutes of Health's National Institute of General Medical Sciences.

When drought-tolerant plants detect dry conditions, they synthesize abscisic acid, which causes changes from root tips to leaves and flowers.

Plants under the influence of this hormone begin to conserve water. Their seeds lie dormant in the ground. Their leaves close microscopic pores to stop water loss.

They slow their own growth, and they signal numerous genetic changes, reprogramming themselves to accomplish their single most pressing goal - survival.

"Abscisic acid triggers an array of plant drought-tolerance mechanisms," said co-investigator Julian Schroeder of UC San Diego.

Earlier this year, the picture of how abscisic acid works became clearer when two separate groups of scientists discovered a cluster of genes associated with the hormone.

Simultaneous mutations in four of these related genes led to a greatly impaired abscisic acid response and reduced drought resistance.

Getzoff said that the structure might reveal new ways of improving drought tolerance in plants.

Such improvements would be a boon for agriculture, which is the single largest use for water in most of the world, consuming up to 90 percent of available water in some of the hottest and most arid parts of the world, which are often prone to drought.

One possible way to translate this research to agricultural products would be to design chemicals to mimic the action of abscisic acid, according to Getzoff.

Such chemicals would then be sprayed on crops to protect them in the face of looming drought.