Isoxaben Inhibits the Synthesis of Acid Insoluble Cell Wall Materials In Arabidopsis thaliana

The effect of the herbicide isoxaben on the incorporation of radiolabeled glucose, leucine, uracil, and acetate into acid insoluble cell wall material, protein, nucleic acids, and fatty acids, respectively, was measured. Dichlobenil, cycloheximide, actinomycin D, and cerulenin, inhibitors of the incorporation of these precursors into these macromolecular components, functioned as expected, providing positive controls. The incorporation of radiolabeled glucose into an acid insoluble cell wall fraction was severely inhibited by isoxaben at nanomolar concentrations. Amitrole, fluridone, ethalfluralin, and chlorsulfuron, as well as cycloheximide, actinomycin D, and cerulenin did not inhibit incorporation of glucose into this fraction, ruling out a general nonspecific effect of herbicides on glucose incorporation. The evidence thus suggests that isoxaben is an extremely powerful and specific inhibitor of cell wall biosynthesis.