Subcellular localization of plastoquinane and ubiquinone synthesis in spinach cells

In vivo labeling of spinach etiolated leaves with [H-3]mevalonate followed by rapid cell fractionation procedure showed that ER-Golgi membranes are in volved in transport of plastoquinone (PQ) and ubiquinone (UQ) to plastids a nd mitochondria, respectively. Translocation of these lipids was inhibited by agents which affect protein and lipid intracellular transport causing st ructural and functional disintegration of the ER-Golgi system (monensin, br efeldin) and interfere with mitochondrial energy conservation (carbonyl cya nide m-chlorophenylhydrazone), but was not affected by colchicine which inf luences the organization of the cytoskeletal network. Colchicine treatment resulted in marked stimulation of PQ and UQ synthesis. Results of experimen ts with pre-exposure of etiolated seedlings to light suggest that transloca tion processes are dependent on the plastid developmental state and their c apacity as accepters of PQ. Thus, the experiments indicate that biosynthesi s and transport of PQ and UQ involve multiple cellular compartments and tha t kinetics of the transport process is dependent on the actual physiologica l conditions. (C) 2000 Elsevier Science B.V. All rights reserved.