Drought-resistant plants hold key to new food sources

As the southwestern United States continues to experience severe drought conditions, and climate change continues to increase the likelihood of future droughts, scientists are studying how drought-resistant plants conserve water. The genetic and metabolic mechanisms used to minimize water loss could be key to developing drought-resistant food and bioenergy crops.

A team of scientists from the Department of Energy’s Oak Ridge National Laboratory have studied and identified these mechanisms in drought-resistant plants in a report published in Nature Plants. Certain plants found in semi-arid climates, such as agave, adapted to their dry environment by developing an alternative form of photosynthesis known as crassulacean acid metabolism (CAM). In CAM, the plants absorb and store carbon dioxide through their pores at night when water is less likely to evaporate. During the day, while the plant uses sunlight to turn carbon dioxide energy, the pores stay closed and minimize water loss.

While scientists have been aware of the CAM process since the 1950s, there has still been much mystery surrounding how exactly it works. But the team of researchers from the Oak Ridge National Library conducted a study to determine which metabolic mechanisms allow the plant to photosynthesize this way. The ultimate goal, they say, is to introduce these water-saving traits into food sources and bioenergy to offer solutions during severe droughts.

According to Xiaohan Yang, coauthor the study, “Today’s demand on agricultural systems to provide food, feed, forage, fiber and fuel call for more comprehensive research into understanding the complexities of CAM plants. As we uncover each layer of the CAM process, our studies aim to speed up the evolution of crops to give them the ability to thrive in more arid environments as the availability of freshwater becomes limited.”

The team compared the molecular traits of agave with a Arabidopsis, a plant that conducts standard photosynthesis. Over a 24-hour period, the team studied the genetic behavior that prompts stomatal movement in the plant. They found the time of day that stomatal activity occurred varied greatly between the two plants, and also successfully determined which mechanisms prompt the pores to open and close. By understanding the timing and rhythm of the CAM process, scientists can parlay the process into crops like rice and corn.

Said coauthor Gerald Tuskan, “Further research is required to understand how this molecular timekeeping regulates CAM, but the results of this study provide new insights into the complexity of CAM biodesign, featuring an integrative understanding of CAM at the molecular level. The transfer of CAM molecular machinery into energy crops would facilitate their deployment onto marginal lands and would simultaneously reduce competition with food crops.”