The abscissic acid (ABA) transduction cascade following the plasmalemma perception was analyzed in intact Arabidopsis thaliana suspension cells. In response to impermeant ABA, anion currents were activated and K+ inward rectifying currents were inhibited. Anion current activation was required for the ABA specific expression of RAB18. By contrast, specific inhibition of K+ channels by tetraethylammonium or Ba2+ did not affect RAB18 expression. Thus, outer plasmalemma ABA perception triggered two separated signaling pathways.
