- Program Areas
- Energy and Water
- Environmental Restoration
- Munitions Response
- Resource Conservation and Climate Change
- Weapons Systems and Platforms
Sustainable Range Management of RDX and TNT by Phytoremediation with Engineered Plants
Decades of military activity on live-fire training ranges has resulted in the contamination of land and groundwater by recalcitrant high explosives, in particular, TNT and RDX. TNT and its transformation products are highly toxic, but these tend to bind strongly to clay and organic matter in soil and are largely contained at the site of contamination; however, RDX is a major concern, because of its high mobility through soils and subsequent contamination of groundwater. RDX contamination of training ranges is now proving to be a significant threat to drinking water sources. Currently, there are no cost-effective processes to contain RDX or remediate large areas of contaminated vegetated land on training ranges.
The objective of this project is to engineer transgenic grasses to contain and degrade RDX in the root zone of explosives-contaminated soil. The expression in plants of a novel RDX-degrading cytochrome P450 gene, XplA, will be investigated. This enzyme is known to degrade RDX to harmless metabolites. Since munitions often consist of both RDX and TNT, it also will be necessary to engineer resistance to TNT as this explosive is highly toxic to plants.
Under SERDP project ER-1318, researchers demonstrated that expression of the rhodococcal gene in the model plant system arabidopsis confers the ability to tolerate and degrade high concentrations of RDX. They also demonstrated that expression of the bacterial nitroreductase XplA gene in tobacco and arabidopsis confers resistance to toxic levels of TNT. Researchers have shown that the nitroreductase TNT transformation products are conjugated to sugars as part of the detoxification process in plants; however, experiments using axenic culture systems suggest that this may be a rate-limiting step to removing TNT from the environment. To investigate this observation and to further improve TNT resistance in the RDX-degrading transgenic plant lines, identification and overexpression of appropriate glycosyltransferases will be carried out. The ability of XplA to degrade RDX and the related nitramine explosive HMX in plants will be further improved through methods of random mutagenesis and directed evolution. Arabidopsis will be used as a model plant system; however, the major objective of this project is to generate transgenic plants that can detoxify TNT and remove and degrade RDX at training ranges. The transformed plants must be appropriate for growth on ranges, in particular, low-growing, fire-resistant, and capable of withstanding and recovering rapidly from disruption by heavy equipment. To meet this requirement, researchers will introduce the genes encoding explosives degrading and detoxifying enzymes into a range of grasses of known utility.
This project will result in the development of a variety of grasses with unique abilities to detoxify TNT and degrade RDX. These plants promise to provide a self-sustaining, inexpensive, and environmentally friendly method of range restoration that can be used over large areas of land for preventing groundwater contamination. Engineering plants to remove explosives has the potential to provide an efficacious means to clean up land contaminated through military activities. (Anticipated Project Completion - 2013)
Points of Contact
Dr. Neil Bruce
University of York
Phone: 01904 432618
Fax: 01904 432928
SERDP and ESTCP
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