A bacterial haloalkane dehalogenase gene as a negative selectable marker in Arabidopsis

The dhlA gene of Xanthobacter autotrophicus GJ10 encodes a dehalogenase whi ch hydrolyzes dihaloalkanes, such as 1,2-dichloroethane (DCE), to a halogen ated alcohol and an inorganic halide (Janssen et al., 1994, Annu. Rev. Micr obiol. 48, 163-191). In Xanthobacter, these alcohols are further catabolize d by alcohol and aldehyde dehydrogenase activities, and by the product of t he dhlB gene to a second halide and a hydroxyacid. The intermediate halogen ated alcohols and, in particular, the aldehydes are more toxic than the hal oalkane substrates or the pathway products. We show here that plants, inclu ding Arabidopsis, tobacco, oil seed rape acid rice, do not express detectab le haloalkane dehalogenase activities, and that wild-type Arabidopsis grows in the presence of DCE, In contrast, DCE applied as a volatile can be used to select on plates or in soil transgenic Arabidopsis which express dhlA. The dhlA marker therefore provides haloalkane dehalogenase reporter activit y and substrate dependent negative selection in transgenic plants.