Synthetic Molecule Could Ensure Crop Survival in Face of Climate Change

Botanists have identified an inexpensive synthetic chemical capable of mimicking the plant stress hormone ABA that helps them cope with drought conditions - a discovery researchers and industry giants both believe could be used to help save plants and increase crop yields in a world of increasing weather extremes.

Called quinabactin, the study was led by Sean Cutler, a plant cell biologist at the University of California, Riverside and comes at a time when farmers in the United States are witnessing record-breaking extremes in temperature and drought that have led to increases in the cost of food, feed and fiber throughout the world.

These extremes, according to climate scientists, may be the new normal both in North America and elsewhere, meaning that novel agricultural strategies may become necessary to merely maintain current crop yields.

Naturally, all land plants have intricate water sensing and drought response systems in order to thrive to the best of their capabilities in whatever environment they find themselves in. For example, plants in areas with low water grow slowly so as not to consume more water than is available.

"But since farmers have always desired fast-growing varieties, their most valued strains did not always originate from drought-tolerant progenitors," Cutler, an associate professor of plant cell biology, explained in a press release. "As a result, we have crops today that perform very well in years of plentiful water but poorly in years with little water."

This problem has since led to an active search for drought-tolerant crops and chemicals that farmers can use for aiding their plants during drier years, according to Cutler.

Working on Arabidopsis, a model plant commonly used in plant biology labs, Cutler and his colleagues focused on tinkering with one of the plant endogenous systems involved in drought responses.

Plant leaves are lined with tiny pores, called stomata, which open and close to control the amount of water lost to the environment by evaporation. During times of drought, therefore, the stomata shut tightly to limit water loss. Behind the scenes, ABA orchestrates this process while cells throughout the plant produce increasing amounts of ABA as water levels decrease.

The small hormone then moves throughout the plant, signaling the stressful conditions and prompting the closure of the stomata. Meanwhile, inside plant cells, ABA does its job by turning on a special class of proteins called receptors.

"If you can control the receptors the way ABA does, then you have a way to control water loss and drought-tolerance," Cutler said. "It has been known for many years that simply spraying ABA on plants improves their water use and stress tolerance, but ABA itself is much too expensive for practical use in the field by farmers."

To address this problem, Cutler and his team searched through many thousands of molecules to identify inexpensive synthetic chemicals that could activate the receptors by mimicking ABA, finally discovering and then naming quinabactin, a molecule almost indistinguishable from ABA in its effects, but much simpler chemically and therefore easier to make than ABA.

By studying how the new molecule activates the ABA receptors that are involved in drought tolerance, the team was also able to determine more about the underlying control logic of the stress response system and provide new information for others developing similar molecules.

"This is a competitive arena that includes agrichemical giants who are busily working to bring similar drought-protecting molecules to market, so this is a landmark discovery because quinabactin is the first-in-class synthetic molecule of its kind," Cutler explained.

Ultimately, the study is only the first in a multistep process of bringing a new agricultural product to the market. According to Culter, the UCR Office of Technology Commercialization (OTC) is currently working with agricultural leader Syngenta Biotechnology in order to develop the new technology based on the study's findings.

Study results will appear online this week in the Proceedings of the National Academy of Sciences.