Scientists from the United States and South Korea have now engineered Arabidopsis thaliana to behave like a succulent, improving water-use efficiency, salinity tolerance, and reducing the effects of drought. The work led by University of Nevada, Reno Biochemistry and Molecular Biology Professor John Cushman will be combined with another of his projects: engineering another trait called crassulacean acid metabolism (CAM), a water-conserving mode of photosynthesis that can be applied to plants to improve water-use efficiency.
"Water-storing tissue is one of the most successful adaptations in plants that enables them to survive long periods of drought. This anatomical trait will become more important as global temperatures rise, increasing the magnitude and duration of drought events during the 21st century," said Professor Cushman. He added that the two adaptations work hand-in-hand, and their goal is to engineer CAM. In order to do this efficiently, they engineered a leaf anatomy that had larger cells to store malic acid that accumulates in the plant at night. These larger cells also served to store water to overcome drought and to dilute salt and other ions taken up by the plant, making them more salt tolerant.
The A. thaliana engineered by Cushman's team has increased cell size resulting in larger plants with increased leaf thickness, more water-storage capacity, and fewer and less open stomatal pores to limit water loss from the leaf due to the overexpression of a gene, known as VvCEB1. The gene is involved in the cell expansion phase of berry development in wine grapes.
According to Professor Cushman, CAM plants are very smart, keeping their stomata closed during the day, and only opening them at night when evapotranspiration is low because it is cooler and the sun is not shining. The significance of CAM is found in its unique ability to conserve water. Where most plants would take in carbon dioxide during the day, CAM plants do so at night. CAM plants are also five to six times more water-use efficient, and many desert-adapted CAM plants also have a greater ability to tolerate high temperatures.