Subcellular reorganization of mitochondria producing heavy DNA in aging wheat coleoptiles

Unusual closed membrane vesicles containing one or more mitochondria were i solated from homogenates of aging wheat coleoptiles, Very similar (or the s ame) bodies mere shown to exist in situ in vacuoles of undividing cells in the apical part of intact senescent coleoptiles, Vesicles isolated from col eoptile homogenate free of nuclei by 10 min centrifugation at 1700 X g and traditional mitochondria (sedimented at between 4300 X g and 17 400 X g) ar e similar in respiration rate, composition and content of cytochromes and s ensitivity to respiration inhibitors. However, vesicles contain about 2-fol d more Ca2+ ions than free mitochondria do. The specific feature of vesicle s containing mitochondria in aging coleoptiles is an intensive synthesis of heavy (rho=1.718 g/cm(3)) mitochondrial DNA (H-mtDNA). Thus, aging in plan ts is accompanied by an increased selective H-mtDNA production and change i n subcellular organization of mitochondria, (C) 1999 Federation of European Biochemical Societies.