Frank L. Mena

In order to create a novel mechanism for herbicide resistance in plants, we expressed a single-chain antibody fragment (scFv) in tobacco with specific affinity to the auxinic herbicide picloram. Transgenic tobacco plants and seedlings expressing this scFv against picloram were protected from its effect in a dose-dependent manner. This is the first successful use of an antibody to confer in vivo resistance to a low molecular weight xenobiotic (i.e. < 1000 Da). Our results suggest the possibility for a generic antibody-based approach to create crops resistant to low molecular weight xenobiotics for subsequent use in the bioremediation of contaminated soils, crop protection and as novel selectable markers.

Herbicide safeners have been shown to enhance the selective action of herbicides through a variety of mechanisms and pathways which may involve elevation of detoxification or conjugation reactions, altered transport activities in plants and perhaps antagonistic effects with the herbicide on the physiology of the plant or at the site of action. Most of the known mechanisms of herbicide selectivity in plants are known to be enhanced by one or more safeners. Corn, sorghum and to a lesser extent, wheat, have well-documented mechanisms for detoxifying herbicides through conjugation or oxidative reactions. The tolerance of these crops to a number of herbicides is increased by safeners known to enhance these systems. Most herbicide safeners are remarkably specific in their protection of one plant species, e.g. corn, without reducing the efficacy of the herbicide on weeds.