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Trees with rabbit genes accelerate cleaning of soil

Genetically modified plants that can break down pollutants may be an effective way to clean soil contaminated by industrial chemicals and explosives used by the military, say scientists.

Tests on six-inch tall GM poplar cuttings which had a gene from a rabbit inserted into them showed that they could remove up to 91 per cent of a chemical called trichloroethylene from the water used in their feed. This chemical, used as an industrial degreaser and one of the most common contaminants of ground water, was broken down by the plants into harmless byproducts more than 100 times faster than by unaltered plants.

“In view of their large size and extensive root systems, these transgenic poplars may provide the means to effectively clean sites contaminated with a variety of pollutants at much faster rates and at lower costs than can be achieved with current conventional techniques,” wrote Sharon Doty, of the University of Washington, Seattle, on Monday in the Proceedings of the National Academy of Sciences (PNAS).

The GM poplars also broke down other common environmental pollutants such as chloroform, a byproduct of the disinfection of drinking water, the solvent carbon tetrachloride, and vinyl chloride, used to make plastics. Poplars use an enzyme called cytochrome P450 to break down contaminants. Trichloroethylene is turned into a harmless salt, water and carbon dioxide.

After Dr. Doty’s team inserted the gene into the tree from a rabbit they also produced P450, but at a much faster rate. Ultimately, the scientists would like to manipulate the plant’s own genes to achieve the same goal.

Another study, also published in the PNAS, demonstrated a way to break down the military explosive RDX. “Widespread contamination of land and ground water has resulted from the use, manufacture, and storage of the military explosive ... RDX. This contamination has led to a requirement for a sustainable, low-cost method to remediate this problem,” wrote Neil Bruce, of the University of York. “One of the biggest concerns of RDX as a pollutant is that it migrates readily through soil into the ground water and subsequently contaminates drinking water supplies.” His team genetically modified Arabidopsis plants to express enzymes called XplA and XplB, which are known to break down RDX. At their best, the plants reduced RDX concentrations from soil by up to 97 per cent in one week.

Though the GM plants may be an effective way to treat pollutants, Dr. Doty acknowledged that people might have concerns at the thought of forests of GM trees. In the United States and Britain, such plants can currently only be grown for research purposes. Dr. Doty added that poplars were fast-growing and could grow for several years without flowering, so there was reduced risk of their genes being transferred into wild populations of the tree. — ©Guardian Newspapers Limited, 2007

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