New molecules to keep plants calm

The phytohormone abscisic acid (ABA) plays an important role in how plants endure certain stresses, such as drought and high salinity. Recent research outlined how this signaling molecule interacts with a family of 14 receptors, collectively known as PYR/PYL receptors, during times of stress¹.

During easy-going, stress-free periods, the concentration of ABA in plant tissues remains at a level high enough to activate some of these receptors. This drove a team of researchers, including two researchers from the King Abdullah University of Science and Technology, Saudi Arabia, to ponder whether there are antagonists to these receptors that counter the basal levels of ABA normally present in plant tissues.

They found that pyrabactin, a synthetic sulfonamide, has both agonist and antagonist properties, depending on which receptor it binds to. When it binds to the receptor PYL1, it mimics the action of ABA, binding to the same spots on the receptor and pulling it into the closed, active position. When it binds to PYL2, however, it occupies the same pocket that binds ABA but does not activate it, effectively blocking its action².

Given the central role that ABA plays in plant resistance to environmental stressors, the researchers believe the discovery of how agonists and antagonists of ABA receptors work might open new avenues for producing other molecules that mimic ABA. These new compounds could be used to produce crops with increased yield under stressful conditions.

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