The first and essential step of phytohormone indole-3-acetic acid (IAA or auxin) signalling – perception has been investigated by means of biochemical-molecular approaches. The subcellular localization of its perception (recognition and binding) sites, specific auxin binding proteins (ABPs) and peculiarities of ABP macromolecules and IAA ligand interactions in different compartments of kidney bean (Phaseolus vulgaris L.) cells were carried out. The description of basic characteristics of individual IAA-ABP complexes formed in separate subcellular compartments – plasmalemma, chloroplast and mitochondria (EC50, KD, n, specificity, etc.) were presented. These characteristics were compared with those of IAA-ABP1 from plasmalemma, which mediates cell response to IAA by enlargement. For the first time, the obtained results led to predict that the chloroplast may have a potential to take stand in cellular IAA signaling, at least by regulating IAA distribution in cell.
Keywords: auxin binding proteins (ABPs), kidney bean, chloroplast, plasmalemma, mitochondria.