With farmers looking back on the latest ‘warmest year on record’, researcher are looking for ways to make agricultural crops better able to withstand changing weather conditions. Recently, a team led by the University of California, Riverside’s Sean Cutler has developed a method to tweak the internal chemistry of plants to make them more drought resistant and they’ve done it using chemicals already widely used in agriculture.

California and the entire US Southwest is currently experience a multi-year drought and those states are not alone. According to The International Fund for Agricultural Development (IFAD), 12 million hectares of agricultural lands are turning to desert annually. Meanwhile some areas of the world are losing crops due to unusually high levels of flooding and all of this is happening while the global population grows by more than 200 thousand people per day.

As the climate changes, developing plants that are better able to withstand changing conditions may become critical for global food supplies.

When faced with drought conditions, plants naturally release the stress hormone abscisic acid (ABA). The hormone reduces water consumption and inhibits growth, essentially slowing the plants metabolic system until more water is available.

When the ABA is activated, it turns on a receptor in plants which causes the plant to take certain actions beneficial to drought survival. This includes closing stomata on leaves. The stomata are pores which facilitate gas exchange in plants. They are formed by a pair of guard cells which regulate the opening and closing of the pores. By closing the gas exchange openings the plants lose water more slowly.

ABA can be artificially sprayed on plants to artificially trigger drought reactions. However, ABA is expensive to produce and not particularly effective. When sprayed with ABA, plants rapidly work to deactivate it. As a side effect they also become more light sensitive.

Research is currently being done to create less expensive synthetic ABA. Those projects, even if successful, face lengthy development and approval processes.

Cutler’s team took a different approach to the problem. The researchers modified the existing ABA receptors of test plants so that the receptors were triggered by mandipropamid instead.

Mandipropamid is a fungicide already widely used to control late blight in crops.

In a paper published in the February 4 issue of Nature, the researchers demonstrated that the reprogrammed plants respond to mandipropamid by switching on the ABA pathway. The stomata on the leaves were closed and water loss was reduced. This has the effect of creating increased drought resistance using a chemical with would have been used anyway.

“We successfully repurposed an agrochemical for a new application by genetically engineering a plant receptor – something that has not been done before. We anticipate that this strategy of reprogramming plant responses using synthetic biology will allow other agrochemicals to control other useful traits – such as disease resistance or growth rates, for example,” said Cutler, in a statement.

This approach has the added benefit of bypassing the lengthy approval process for new agricultural chemicals.

“We have, in effect, circumvented this hurdle using synthetic biology – in essence, we took something that already works in the real world and reprogrammed the plant so that the chemical could control water use,” said Cutler.

To date the approach has only been tried using tomato plants and it will likely take some time before it can be tested with other crops.