Further Characterization of the Presumptive Auxin Transport Carrier Using Monoclonal Antibodies

Abstract

A key prediction of the chemiosmotic hypothesis of polar auxin movement [3, 9, 10] is that the carrier by which auxin anion molecules leave a transporting cell is located in differentially greater numbers at the cell’s basal end. In order to visualize the auxin anion carriers (AAC), we have made monoclonal antibodies (Abs) against the naphthyl-phthalamic acid (NPA) receptor in etiolated pea stem tissue and used those antibodies in indirect immunofluorescence experiments [4]. Our presumption was that the receptor for NPA, a specific auxin transport inhibitor believed to act at the basal efflux site [1, 11], would be the same protein as, or closely associated with, the AAC. Our results have led us to the general conclusion that within the resolving power of our technique, the preponderance of sites in etiolated pea third internode tissue is at the basal ends of cells sheathing the vascular bundles (Fig. 1).