Indoleacetic acid pretreatment of tobacco plants in vivo increases the in vitro sensitivity to auxin of the plasma membrane H(+)-ATPase from leaves and modifies the polypeptide composition of the membrane.

The sensitivity to auxin of the H(+)-ATPase-mediated proton translocation was investigated in vitro using purified plasma membrane vesicles from tobacco leaves. In vivo pretreatment of tobacco plants with auxin promotes a 100-fold increase of the in vitro sensitivity to auxin. This effect is specific for biologically active auxins and is dose- and time-dependent. In addition, pretreatment with auxin induces the accumulation of several polypeptides in the plasma membrane. These polypeptides constitute the first set of hormone-responsive polypeptides evidenced in plant membranes.