Dec. 14, 2016
As part of an effort to develop drought-tolerant crops, food, and bioenergy, scientists at the Oak Ridge National Laboratory (ORNL) of the US Department of Energy have discovered the genetic and metabolic mechanisms that allow certain plants to preserve water and thrive in semi-arid climates.
Semi-arid plants like the agave have adapted to survive in areas with little rain, developing a specialized mode of photosynthesis called acid metabolism of the crassulaceae, or CAM. Unlike plants in more humid environments, CAM plants absorb and store carbon dioxide through open pores in their leaves at night, when water is less likely to evaporate. During the day, pores, also called stomas, remain closed while the plant uses sunlight to convert carbon dioxide into energy, minimizing water loss.
ORNL scientists are studying the unique metabolic mechanisms that allow CAM plants to conserve water, with the aim of introducing water-saving traits into food crops and bioenergy products. The results of the team's latest study, which focuses on the agave, were published in Nature Plants, highlighted as the cover of the magazine.
The CAM photosynthetic process, discovered in the 1950s, has largely remained a scientific curiosity, but researchers are now examining it as a potential solution to maintain food and bioenergy production during times of water scarcity and drought.
"Current demand for agricultural systems to provide food, feed, fiber, and fuel requires more thorough research to understand the complexities of CAM plants," said the ORNL study's co-author Yang Xiaohan. "As we discover each layer of the CAM process, our studies aim to accelerate the evolution of crops to give them the ability to thrive in more arid environments, as freshwater availability becomes limited."
To obtain a comprehensive view of the complex CAM system, the team used ORNL mass spectrometry to compare the molecular traits of agave with a control plant, Arabidopsis, using a more common photosynthetic process.
The team evaluated the genetic behavior responsible for the stomatal movement in each plant during a period of 24 hours. Their study revealed that the timing of daytime stomatal activity versus nocturnal activity varied significantly between agave and Arabidopsis. The research also pointed out what genetic and metabolic mechanisms signal CAM plants to open and close their stomata. Understanding the timing of these signals will be key for transferring CAM processes to crops such as rice, maize, poplar, and forage grassland.
"More research is needed to understand how this molecular timing regulates CAM, but the results of this study provide new insights into the complexity of CAM biology, with an integrative understanding of CAM at the molecular level," stated Gerald Tuskan, corporate Fellow at ORNL and coauthor of the study. "The transfer of CAM molecular machinery to energy crops would facilitate their deployment on marginal lands and simultaneously reduce competition with food crops."