AUXINS INDUCE CLUSTERING OF THE AUXIN-BINDING PROTEIN AT THE SURFACE OF MAIZE COLEOPTILE PROTOPLASTS

The predominant localization of the major auxin-binding protein (ABP1) of maize is within the Lumen of the endoplasmic reticulum. Neverthele ss, all the electrophysiological evidence supporting a receptor role f or ABP1 implies that a functionally important fraction of the protein must reside at the outer face of the plasma membrane. Using methods of protoplast preparation designed to minimize proteolysis, we report th e detection of ABP at the surface of maize coleoptile protoplasts by t he technique of silver-enhanced immunogold viewed by epipolarization m icroscopy. We also show that ABP clusters following auxin treatment an d that this response is temperature-dependent and auxin-specific.