By Brian Sodoma
Every living thing brings its own natural responses to stress. When critical nutrients are in short supply, our bodies, for example, find ways to maintain normal function until those nutrients are replenished. Plants do the same. In drought conditions, natural processes kick in to keep them alive until they can be watered again.
But Sean Cutler knows that with the help of protein engineering, some plants can last even longer in a drought.
The UC Riverside assistant professor's insights are well timed, as California endures its worst drought in history. 2014 was the driest on record in the Golden State and Cutler's research could buy some necessary time for water-starved plants.
“It looks pretty clear that the water problem is going to keep getting worse, which will bring pressure for solutions," Cutler said.
Early Experiments
When faced with a water shortage, plants produce a stress hormone known as abscisic acid (ABA), which signals the plant to consume less water. ABA binds to a specific protein receptor in the plant, signaling stomata—or unique guard cells—to close and reduce the amount of water lost. This receptor is so important that its discovery by Cutler, his team and others was listed as one of 2009's breakthroughs of the year by Science magazine.
To help plants survive extreme drought conditions, some have tried spraying ABA directly on crops during water shortages. The move can improve crop yields, but ABA is expensive to produce and breaks down easily, even before a plant can absorb and use it.
Cutler's team wondered, what if they took an existing agrochemical that is proven in the market and reprogrammed the plant's ABA receptor to recognize it instead of ABA? So Cutler's team created its own version of the ABA receptor and programmed it to bind to mandipropamid, or Mandy, a fungicide used to prevent late blight in fruits and vegetables since 2008.
Over the years, the team developed a keen knowledge of how the ABA receptor works. They tinkered with it so that it could bind to Mandy and allow Mandy to be used to control water consumption. They essentially reprogrammed the plant so that it thinks Mandy is the natural hormone, which gave them a chemical means to improve drought tolerance.
“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.
Cutler said the technology is like inserting an “internal defense" against water shortages.
“We know how long we can withhold water from a normal plant before it's past the point of no return," he said. “This strategy can buy time."
From Flower to Farmland
In an experiment published in the scientific journal Nature earlier this year, Cutler's team used the reengineered protein in tomato plants and Arabidopsis, a relative of the mustard seed plant.
The plants went 12 days without water and were revived after being rewatered. Meanwhile, the plants without the reengineered receptor died even after reintroducing water.
Cutler said the technology could be used to recover some of the crop yield that normally is lost to drought; however, when using it, a farmer hits the “pause" button on growth in an effort to conserve water. If a large supply of water unexpectedly became available, there is a risk that overall yield could be compromised compared to if had the farmer not hit the “pause” button.
“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."
The next step will be to test the plants containing the reengineered protein in a real farming environment. The approach could be useful for large-scale crops like corn or soy, Cutler added, and UCR's Office of Technology Commercialization has filed a patent application for the technology. Mandy's manufacturer, Syngenta, and The National Science Foundation supported the research efforts.
The professor said it could take up to 10 years before the concept is perfected. But he is also confident that the reengineered receptor his team has created can be used in many different plants.
“I think we can investigate a lot of new biology with this system," he added.
Brian Sodoma is a journalist who covers business and health, but is always on the lookout for interesting people in any field. He lives in Southern Nevada.
