Plant ABC transporters

The ATP binding cassette (ABC) superfamily is a large, ubiquitous and diver se group of proteins, most of which mediate transport across biological mem branes. ABC transporters have been shown to function not only as ATP-depend ent pumps, but also as ion channels and channel regulators. Whilst members of this gene family have been extensively characterised in mammalian and mi crobial systems, the study of plant ABC transporters is a relatively new fi eld of investigation. Sequences of over 20 plant ABC proteins have been pub lished and include homologues of P-glycoprotein, MRP, PDR5 and organellar t ransporters. At present, functions have been assigned to a small proportion of these genes and only the MRP subclass has been extensively characterise d. This review aims to summarise literature relevant to the study of plant ABC transporters, to review methods of cloning, to discuss the utility of y east and mammalian systems as models and to speculate on possible roles of uncharacterised ABC transporters in plants. (C) 2000 Elsevier Science B.V. All rights reserved.