In order to investigate the effect of the rol A gene product on the plasma membrane response to auxin, a clone of rol A-transformed tobacco was prepared. Auxin sensitivity was measured by the auxin concentration which induced the highest stimulation of H+-ATPase-mediated proton translocation on isolated plasma membrane vesicles. Both transformed and control plants exhibited identical auxin-sensitivity changes during vegetative and induction to flowering periods. However the sensitivity of flowering-transformed plants Was 100-times higher than that of control plants. Consistent observations were also made when using rol A+B+C-transformed plants. These results suggest that the rol A gene product could either participate in or affect the reception/transduction pathway of auxin signal at the plasma membrane.
