Structure of Phytohormone Receptor Reveals New Ways of Improving Drought Tolerance

Researchers at the Scripps Research Institute and the University of California, San Diego have produced a three-dimensional representation of the important phytohormone abscisic acid (ABA), attached to its target protein called PYR1. ABA is produced by plants in large amounts during times of stress, and particularly during conditions of drought. Plants under the influence of this hormone begin to conserve water. However, the exact molecular mechanism by which ABA helps plants tolerate drought remains poorly understood. Understanding the inner workings of this molecule may help scientists design new ways to protect crops against prolonged dry periods, potentially improving crop yield worldwide.

The search for the molecules that regulate the ABA signaling pathway has been going on for sometime. Recently, a team of researchers, led by Sean Cutler, successfully pinpointed a protein that plays a linchpin role in the relay of ABA signals: PYR1.

Cutler's work led to the current study. "This early research with Sean led to new important questions," said Julian Schroeder, co-author of the research. "We wanted to know if abscisic acid bound specifically to the PYR1 protein as a hormone receptor or whether it acted like a glue between PYR1 and partner proteins."

The research showed that two copies of PYR1 fit snugly together in plant cells. There, they are targeted by abscisic acid. Each copy of the PYR1 molecule has an internal open space like the inside of a tin can, and when a hormone molecule comes along, it fits neatly into one of the two spaces. This induces part of the PYR1 protein that the team calls the "lid" to close.

"One possible way to translate this research to agricultural products would be to design chemicals to mimic the action of abscisic acid," noted EliGetzoff, co-author of the paper. "Such chemicals would then be sprayed on crops to protect them in the face of looming drought."

The paper published by Science is available to subscribers at http://dx.doi.org/10.1126/science.1181829 For more information, read http://ucsdnews.ucsd.edu/newsrel/science/10-09Drought.asp

A related article can be found at http://www.isaaa.org/kc/cropbiotechupdate/sentarticle/default.asp?ID=4138