Plants have inherent traits to minimise water loss

Understanding of a key biochemical reaction could help future farmers protect plants from drought. Climate change will bring worsening droughts that threaten crops.

One potential way to protect crops is by spraying them with a compound that induces the plants to become more drought resistant. Now, by identifying the key molecular mechanism that enables a plant to minimize water loss, researchers may be one step closer to that goal.

Faced with dry conditions, plants can mount a natural defense. They produce a hormone, called abscisic acid, or ABA, that binds to a protein, called a PYL receptor, triggering a chain of reactions that eventually closes the plant's pores on its leaves.

"There is no or little water loss from the plants," explained Saurabh Shukla, a graduate student at the University of Illinois. "They conserve water resources and they survive for longer periods of time."

The key is the ABA hormone. Because of its moderate stability and molecular complexity, ABA can't be directly sprayed in fields. But, Shukla said, "If we can understand how the hormone works, we can design some molecule that can be sprayed and does the same job for us."

If researchers can find a molecule that not only works the same way as the ABA hormone, but also is cheap, stable and environmentally friendly, then farmers can use it to make their crops become drought-resistant.

But the details for how ABA works have been elusive. Experimental techniques such as X-ray diffraction can take snapshots of the hormone before and after binding to the PYL receptor, but they can't catch the two in the act. So Shukla and his colleagues turned to supercomputers.

Using molecular dynamic simulations, the researchers have, for the first time, revealed the molecular details for how ABA binds with the PYL receptor.

The simulations show, frame by frame, how and where the hormone binds with the protein and causes it to change shape, which allows it to activate the next protein in the sequence that eventually enables the plant to close its pores.