Transport of primary metabolites across the plant vacuolar membrane.
Mesophyll cells and most types of storage cells harbor large central vacuoles representing the main cellular store for sugars and other primary metabolites like carboxylic- or and amino acids. The general biochemical characteristics of sugar transport across the vacuolar membrane are already known since a couple of years but only recently the first tonoplast sugar carriers have been identified on the molecular level. A candidate sucrose carrier has been identified in a proteomic approach. In Arabidopsis, the tonoplast monosaccharide transporters (TMT) represent a small protein family comprising only three members, which reside in the vacuolar membrane. Two of three tmt genes are induced upon cold, drought or salt stress and tmt knock out mutants exhibit altered monosaccharide levels upon cold induction. These observations indicate that TMT proteins represent the first examples of tonoplast sugar carriers involved in the cellular response upon osmotic stress stimuli.
Neuhaus
H Ekkehard
HE
Pflanzenphysiologie, Technische Universitat Kaiserslautern, Postfach 3049, D-67653 Kaiserslautern, Germany. neuhaus@rhrk.uni-kl.de
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001693:Biological Transport, Active; D050260:Carbohydrate Metabolism; D004187:Disaccharides / Q000378:metabolism; D017343:Genes, Plant; D007425:Intracellular Membranes / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism; D009005:Monosaccharides / Q000378:metabolism; D009997:Osmotic Pressure; D010944:Plants / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism
D029681:Arabidopsis Proteins; D004187:Disaccharides; D009004:Monosaccharide Transport Proteins; D009005:Monosaccharides; C518496:Tmt1 protein, Arabidopsis; C518497:Tmt2 protein, Arabidopsis; C518498:Tmt3 protein, Arabidopsis