As part of an effort to develop drought-resistant food and bioenergy crops, scientists at the Department of Energy’s Oak Ridge National Laboratory have uncovered the genetic and metabolic mechanisms that allow certain plants to conserve water and thrive in semi-arid climates.
Semi-arid plants such as agave have adapted to survive in areas with little rainfall by developing a specialized mode of photosynthesis called crassulacean acid metabolism, or CAM.
ORNL scientists are studying the unique metabolic mechanisms that allow CAM plants to conserve water, with the goal of introducing water-saving traits into bioenergy and food crops.
The results of the team’s latest study, which focuses on agave, are published in Nature Plants.
To gain a comprehensive view of the complex CAM system, the team used ORNL’s mass spectrometry to compare the molecular traits of agave with a control plant, Arabidopsis, which uses a more common photosynthetic process.
Their study revealed that the timing of daytime versus nighttime stomatal activity varied significantly between agave and Arabidopsis.
The research also pinpointed which genetic and metabolic mechanisms signal CAM plants to open and close their stomata.
Understanding the timing of these signals will be key to transferring CAM processes into crops such as rice, corn, poplar and switchgrass.
"The transfer of CAM molecular machinery into energy crops would facilitate their deployment onto marginal lands and would simultaneously reduce competition with food crops."
Journal Reference: Paul E. Abraham, Hengfu Yin, Anne M. Borland, Deborah Weighill, Sung Don Lim, Henrique Cestari De Paoli, Nancy Engle, Piet C. Jones, Ryan Agh, David J. Weston, Stan D. Wullschleger, Timothy Tschaplinski, Daniel Jacobson, John C. Cushman, Robert L. Hettich, Gerald A. Tuskan, Xiaohan Yang.

How tequila could be key in our battle against climate change.
Agave — the cactus-like plant which forms the base ingredient of tequila — has a nocturnal ‘body clock’ which allows it to ‘breathe’ at night and withstand the driest of conditions, new research has shown.
Publishing their findings in this month’s Nature Plants, the team from Newcastle University, UK, and Oak Ridge National Laboratory, Tennessee, reveal for the first time how the stomata — or ‘breathing’ pores — on the Agave’s leaves are kept shut during the day to minimise water loss.
Newcastle University’s Professor Anne Borland, one of the authors of the study, explains: "Photosynthesis needs three key ingredients — CO2, water and sunlight — so it follows that most plants keep their stomata open in the day when it is sunny and shut at night when it is dark.
"But for a plant living in hot, arid conditions such as the Agave, this would be disastrous.
They need to conserve every drop of water they can and leaving their stomata open during the day would result in such rapid water loss they would simply die.
"If we can harness these genes and engineer new drought-resistant plants then the potential is huge in terms of developing crops and biofuels that are able to withstand the challenges we face from a changing climate."
Sequencing thousands of genes and proteins to understand the underlying metabolic processes, the team compared the Agave — or CAM — plant with Arabidopsis, a type of cress and a typical C3 plant.
"This is a really exciting discovery and a major breakthrough in our quest to create new plants that can cope in our future environment."
The study is part of a $14m research programme funded by the Department of Energy Office of Science Genomic Science Programme.