SUGAR-TRANSPORT ACROSS THE PLASMA-MEMBRANES OF HIGHER-PLANTS

The fluxes of carbohydrates across the plasma membranes of higher-plan t cells are catalysed mainly by monosaccharide and disaccharide-H+ sym porters. cDNAs encoding these different transporters have been cloned recently and the functions and properties of the encoded proteins have been studied extensively in heterologous expression systems. Several of the proteins have been identified biochemically in these expression systems and their location in plants has been shown immunohistochemic ally or with transgenic plants which were transformed with reporter g enes, expressed under the control of the promoters of individual trans porter genes. In this paper we summarize the current knowledge on the molecular biology and biochemistry of higher-plant sugar transport pro teins.