Colchicine-binding tubulin was isolated from the centre 2 axoneme microtubules from the flagella of the alga Chlamydomonas eugametos. Incubating this tubulin with 5–8 micron [14C]trifluralin resulted in significant and reproducible binding of trifluralin to tubulin. The specificity of binding was determined by demonstrating that limited or no binding occurred to flagellar membrane and matrix protein, higher plant proteins, or bovine serum albumin. It was concluded that trifluralin, at obtainable soluble concentrations, specifically inhibits microtubule-mediated processes in plants. To date no effect of trifluralin on animal microtubule systems has been reported; therefore, it is suggested that trifluralin has revealed a pharmacological difference between plant and animal tubulin.

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