Agriculture is a thirsty business, currently consuming 90 percent of global freshwater. Calls to increase production to feed and fuel growing populations do not bode well for the sustainability of freshwater supplies. Now, researchers report the use of genetic engineering to reduce water requirements in this sector. Altering the expression of one gene common to all plants improves how a crop uses water by 25 percent without compromising yield.

An international team increased the levels of a photosynthetic protein, Photosystem II Subunit S (PsbS), to Engineered plants conserve 25 percent more water by only partially opening stomata, allowing less water to escape through transpiration while carbon dioxide enters the plant to fuel photosynthesis. Source: Jiayang Xie, Katarzyna Glowacka, Andrew D. B. Leakey/University of Illinoisconserve water by tricking plants into partially closing their stomata, the microscopic pores in leaves that allow water to escape. When stomata are open, carbon dioxide enters the plant to fuel photosynthesis, but water is allowed to escape through the process of transpiration.

Water-use-efficiency — the ratio of carbon dioxide entering the plant to water escaping — improved by 25 percent without significantly sacrificing photosynthesis or yield in real-world field trials.

Atmospheric carbon dioxide concentration has increased by 25 percent in just the past 70 years, allowing plants to amass enough carbon dioxide without fully opening stomata.

PsbS is a key part of a signaling pathway in the plant that relays information about the quantity of light. By increasing PsbS, the signal says there is not enough light energy for the plant to photosynthesize, which triggers the stomata to close since carbon dioxide is not needed to fuel photosynthesis.

The method was tested using tobacco, a model crop that is easier to modify and faster to test than other crops. Researchers will next apply their discoveries to improve the water-use-efficiency of food crops and test their efficacy in water-limited conditions.

Scientists from University of Illinois, University of California-Berkeley, U.S. Lawrence Berkeley National Laboratory, University of Lancaster (UK) and Polish Academy of Sciences participated in this research, which is published in the journal Nature Communications.