Scientists have revealed that a simple genetic tweak to overexpress a single protein in crops could result in the plants needing up to 25 percent less water to produce a regular yield. It's hoped the breakthrough research will lead to a new generation of water-efficient agriculture that helps communities grow more food in areas struggling with drought and climate change.

The research, from an international team of scientists led by the University of Illinois, discovered that a specific protein called Photosystem II Subunit S (PsbS) can be increased to force a plant to partially close its stomata. The stomata, tiny pores in a leaf, open and close to either let carbon dioxide in or oxygen out, regulating the process of photosynthesis.

The initial hypothesis was that by limiting the stomata opening a plant would not lose as much water through transpiration, and subsequently not need as much water to grow. Since atmospheric carbon dioxide has increased by 25 percent in less than a century, the researchers suspected that a plant could still take in all the carbon dioxide it needed with less opening of the stomata.

"Evolution has not kept pace with this rapid change, so scientists have given it a helping hand," says Stephen Long, director of Realizing Increased Photosynthetic Efficiency (RIPE), the international research project behind the study.

The hypothesis was tested in a tobacco crop and the results were incredible. By increasing PsbS expression stomatal openings were reduced, and the ratio of carbon dioxide going into a plant to water escaping improved by 25 percent. This effectively meant the plant would need 25 percent less water to achieve the same rate of photosynthesis. The experiment also showed no significant difference in overall yield or size between modified and non-modified plants.

"This is a major breakthrough," says Long. "Crop yields have steadily improved over the past 60 years, but the amount of water required to produce one ton of grain remains unchanged – which led most to assume that this factor could not change. Proving that our theory works in practice should open the door to much more research and development to achieve this all-important goal for the future."

A startling 90 percent of the world's supply of fresh water is consumed by agriculture. With some estimates suggesting a 70 percent increase in food production will be necessary by 2050, increasingly volatile and erratic climate patterns around the world mean the availability of water to grow these much needed crops may not be easily generated.

While the easy modification and fast lifecycle of tobacco crops proved a successful case study for the process, the next stage for the research is to test it in food crops in conditions simulating water-limited conditions. The research suggests that since the role of PsbS in plants is relatively universal this process should be similarly effective when transferred to common food crops.

"Making crop plants more water-use efficient is arguably the greatest challenge for current and future plant scientists," say co-first author on the study Johannes Kromdijk. "Our results show that increased PsbS expression allows crop plants to be more conservative with water use, which we think will help to better distribute available water resources over the duration of the growing season and keep the crop more productive during dry spells."

The study was published in the journal Nature Communications.

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