Increasing expression of a protein involved in photosynthesis in tobacco can reduce the amount of water the plants lose by 25%, according to a study in Nature Communications. The findings could have implications for increasing crop production with limited water supplies.

Drought is a global problem and producing enough food to feed the increasing world population with less irrigation water is increasingly important. Plants lose absorbed water through pores in leaves called stomata, which allow carbon dioxide (CO2) to enter for photosynthesis. Thus, balancing water loss and CO2 acquisition holds the potential to increase crop water-use efficiency. However, limited advances have been made so far.

Stephen Long and colleagues show that upregulating the expression of a protein called photosystem II subunit S (PsbS), involved in photosynthesis, can increase water-use efficiency without having a negative effect on the uptake of CO2. In field trials, tobacco plants that overexpressed PsbS lost on average 25% less water than wild-type plants. The authors suggest that overexpression of PsbS causes a chain of events leading to a reduction in stomatal opening in response to light and, consequently, decreases water loss.

Since the role of PsbS is universal across green plants, the authors argue that it is likely the strategy developed here can be applied to other crop species to improve water-use efficiency.