Exploiting plants’ natural response to stress caused by drought, researchers have engineered crops that build tolerance and can withstand longer without water, while also extending the point of no return when no amount of water can save the withered plant. This “buy more” time method might hopefully help vulnerable crops fare better during long periods of drought – like the one currently in full swing in California, which is experiencing its worst drought in recorded history – and increase yields.

Photo: greenlichen.com

When our bodies are deprived of water or food, it releases hormones that help conserve energy and resources. Similarly, when there’s not enough water for optimal operation, plants release a stress hormone called abscisic acid (ABA).  Sean Cutler, an assistant professor at UC Riverside, and his team discovered that ABA binds to a specific protein receptors and signals the stomata to close and save water. Some have tried spraying withered plants with ABA to increase their tolerance, and have been somewhat successful. However, synthesizing ABA is expensive and the molecules break down easily, long before the plants even get to absorb and respond.

Faced with this conundrum, Cutler and company took a different route. They engineered their own version of a ABA receptor and programmed it to respond to mandipropamid, or Mandy, a fungicide used to prevent late blight in fruits and vegetables since 2008. In one experiment, the researchers inserted the reengineered protein in tomato plants and a relative to the mustard plant. These plants went for 12 days without water and survived after being watered. In contrast, the control group (normal plants) couldn’t be revived. Findings were reported in Nature.

“We currently have a very detailed picture of how the receptor normally binds to ABA… So we knew which parts of the protein to modify, which was critical to the success of our engineering strategy,” Cutler said.

“We know how long we can withhold water from a normal plant before it’s past the point of no return,” he said for Forbes. “This strategy can buy time.”

Cutler likens the use of the ABA receptor to hitting the “pause button”, something which crops like corn or soy could use in vulnerable situation. It also means that if the crops are in “pause”, but there’s considerable rainfall then the overall yield might be actually much lower.

“The effects are fully dependent on adding this external agent (Mandy). If you amp up the response, you get better drought tolerance, but it can also impact the yield when water is plentiful…It’s a balancing act to minimize impact under ideal conditions.”