The nuclear origin of the non-phosphorylating NADH dehydrogenases of plantmitochondria

The oxidation of matrix and cytosolic NADH by isolated beetroot and wheat l eaf mitochondria was investigated tb determine whether the rotenone-insensi tive NADH dehydrogenases of plant mitochondria were the products of nuclear or mitochondrial genes. After aging beetroot tissue (slicing and incubatin g in a CaSO4 solution), the induction of the level of matrix NADH oxidation in the presence of rotenone was greatly reduced in mitochondria isolated f rom tissue treated with cycloheximide, a nuclear protein synthesis inhibito r. This was also true for the oxidation of cytosolic NADH, Mitochondria iso lated from chloramphenicol-treated tissue exhibited greatly increased level s of both matrix and external rotenone-insensitive NADH oxidation when comp ared to the increase due to the aging process alone. This increase was not accompanied by an increase in matrix NAD-linked substrate dehydrogenases su ch as malic enzyme nor intra-mitochondrial NAD levels. Possible explanation s for this increase in rotenone-insensitive NADH oxidation are discussed. B ased on these results we have concluded that the matrix facing rotenone-ins ensitive NADH dehydrogenase of plant mitochondria is encoded by a nuclear g ene and synthesis of the protein occurs in the cytosol, (C) 1999 Federation of European Biochemical Societies.