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ENVIRONMENTAL STRESS AND ADAPTATION TO STRESS

Engineering a Catabolic Pathway in Plants for the Degradation of 1,2-Dichloroethane^1,[OA]

CNAP, Department of Biology, University of York, York YO10 5YW, United Kingdom (G.L.M.-B., F.G.-H., S.G., T.R.L., S.J.M.-M., E.L.R., N.C.B.); and Institute of Structural and Molecular Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JR, United Kingdom (C.E.F.)

Plants are increasingly being employed to clean up environmental pollutants such as heavy metals; however, a major limitation of phytoremediation is the inability of plants to mineralize most organic pollutants. A key component of organic pollutants is halogenated aliphatic compounds that include 1,2-dichloroethane (1,2-DCA). Although plants lack the enzymatic activity required to metabolize this compound, two bacterial enzymes, haloalkane dehalogenase (DhlA) and haloacid dehalogenase (DhlB) from the bacterium Xanthobacter autotrophicus GJ10, have the ability to dehalogenate a range of halogenated aliphatics, including 1,2-DCA. We have engineered the dhlA and dhlB genes into tobacco (Nicotiana tabacum ‘Xanthi’) plants and used 1,2-DCA as a model substrate to demonstrate the ability of the transgenic tobacco to remediate a range of halogenated, aliphatic hydrocarbons. DhlA converts 1,2-DCA to 2-chloroethanol, which is then metabolized to the phytotoxic 2-chloroacetaldehyde, then chloroacetic acid, by endogenous plant alcohol dehydrogenase and aldehyde dehydrogenase activities, respectively. Chloroacetic acid is dehalogenated by DhlB to produce the glyoxylate cycle intermediate glycolate. Plants expressing only DhlA produced phytotoxic levels of chlorinated intermediates and died, while plants expressing DhlA together with DhlB thrived at levels of 1,2-DCA that were toxic to DhlA-expressing plants. This represents a significant advance in the development of a low-cost phytoremediation approach toward the clean-up of halogenated organic pollutants from contaminated soil and groundwater.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Neil C. Bruce (ncb5{at}york.ac.uk).

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www.plantphysiol.org/cgi/doi/10.1104/pp.108.119008

^* Corresponding author; e-mail ncb5{at}york.ac.uk.

Received March 12, 2008; accepted April 29, 2008; published May 8, 2008.

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On the Inside

Peter V. Minorsky
Plant Physiol. 2008 147: 933-934. [Full Text]