Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2002
Publication Date: 1/15/2003
Citation: GARG, A.K., KIM, J., OWENS, T.G., RANWALA, A.P., CHOI, Y.D., KOCHIAN, L.V., WU, R.J. TREHALOSE ACCUMULATION IN RICE PLANTS CONFERS HIGH TOLERANCE LEVELS TO DIFFERENT ABIOTIC STRESSES. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES. 2003. Interpretive Summary: The explosive increase in world population, along with the continuing deterioration of arable land, scarcity of fresh water and increasing environmental stress are posing serious threats to global agricultural production and food security. In spite of efforts to improve major crops for resistance to abiotic stresses such as drought, excessive salinity and low temperature by traditional breeding, success has been limited. Fortunately, it is now possible to use transgenic approaches in conjunction with breeding to improve abiotic stress tolerance in agriculturally important crops. A common response of organisms to drought, salinity and low-temperature stresses is the accumulation of sugars and other compatible solutes that can serve as osmoprotectants, stabilizing biomolecules under stress conditions. One such compound is trehalose, a sugar made of two glucose molecules, which has been shown to play an important physiological role as an abiotic stress protectant in a large number of organisms including bacteria, yeast and invertebrates. In this study we bioengineered rice to express two key bacterial genes involved in trehalose synthesis. During abiotic stress, the transgenic rice plants accumulated increased amounts of trehalose and showed high levels of tolerance to salt, drought and low-temperature stresses, as compared to the non-transformed plant. These results demonstrate the potential use of these transgenic plants in developing new rice cultivars with increased abiotic stress tolerance and enhance rice productivity.
Technical Abstract: Agricultural productivity is profoundly influenced by abiotic stresses such as drought, salinity and low temperature. In many organisms, the disaccharide trehalose functions as a protectant against these types of stress; however, the mechanism by which trehalose confers protection has not yet been elucidated. We report here that the regulated overexpression of trehalose biosynthetic genes in transgenic rice plants produced increased amounts of trehalose in the shoot and conferred high levels of tolerance to salt, drought and low-temperature stresses. Compared with non-transformed rice, several independent transgenic lines exhibited sustained plant growth, less photo-oxidative damage and more favorable mineral balance under stress conditions. This is the first report of the successful conferment of tolerance to multiple abiotic stresses via overexpression of trehalose synthesis without negative pleiotropic effects. Furthermore, this report provides the first insights into the physiological processes that may be protected from these stresses via trehalose accumulation. Finally, these findings demonstrate the feasibility of engineering rice for abiotic stress tolerance via trehalose overproduction, and thus can decrease in loss of grain yield and increase farm income.