Mitochondrial preparations from the leaves of tobacco (Nicotiana tabacum)

In vitro evaluation of mitochondrial-chloroplast subcellular localization of heme oxygenase1 (HO1) in Glycine max

Heme oxygenase1 (HO1) catalyzes the degradation of heme in to biliverdin, carbon monoxide, and ferrous ions. Its role in higher plants has been found as an antioxidant and precursor of phytochrome synthesis. The present study focuses on subcellular localization of HO1 in leaves of soybean has been investigated. Most activity appeared to be located within chloroplast due to its role in phytochrome synthesis but mitochondria also share its localization. Mitochondrial location of HO1 might be on its inner membranous space due to its role in the synthesis of electron donor species which facilitates HO1 catalyzed reaction. Study reports the co-localization of HO1 in both chloroplast and mitochondria.

The re-assimilation of ammonia produced by photorespiration and the nitrogen economy of C3 higher plants

Photorespiration involves the conversion of glycine to serine with the release of ammonia and CO(2). In C(3) terrestrial higher plants the flux through glycine and serine is so large that it results in the production of ammonia at a rate far exceeding that from reduction of new nitrogen entering the plant. The photorespiratory nitrogen cycle re-assimilates this ammonia using the enzymes glutamine synthetase and glutamine:2-oxoglutarateaminotransferase.

Succinyl CoA Synthetase of Tobacco

The isouition and partial purification of succinyl CoA synthetase from Nicotiana tabacum is described. Enzynio activity had a pH optimum of pH 7.0 and apparent Km values for succinic acid. ATF and MgCl(2) . are 3.5 × 10(-2) 5.7 × 10(-3) and 4.0 × 10(-3) M, respectively. The euzyme is specific in requirement for ATP. Enzyme activity was low in seed, decreased during germination and seedling development, then increased to maximum in physiologically mature leaf tissue. Plauts with the apical apical meristem removed had less euzyme activity in leaves but more enzyme activity in the roots than plants with apical meristem intact. Most enzyme activity observed was associated with the soluble fractions of the cell.

Intracellular localization of nitrate reductase, nitrite reductase, and glutamic Acid dehydrogenase in green leaf tissue

Greenhouse grown seedlings of corn (Zea mays L.) and foxtail (Setaria faberii Herrm.) were used as source material in determining the intracellular localization of nitrate reductase, nitrite reductase, and glutamic acid dehydrogenase, Nonaqueous and aqueous isolation techniques were used to establish that nitrite reductase is localized within the chloroplasts, but that nitrate reductase and glutamic acid dehydrogenase are not. Nonaqueous isolation gives distribution patterns of nitrite reductase which are the same as those observed for NADP-dependent 3-phosphoglyceraldehyde dehydrogenase but which differ drastically from the patterns observed for pyruvic acid kinase. The distribution patterns for nitrate reductase are the same as those of pyruvic acid kinase. The techniques used do not eliminate the possibility that nitrate reductase and pyruvic acid kinase are localized on the external chloroplast membrane.The data obtained establish that glutamic acid dehydrogenase of green leaves is localized within the mitochondria.

FINE STRUCTURAL CHANGES IN ISOLATED MITOCHONDRIA OF HEALTHY AND VIRUS-INFECTED VICIA FABA L

Mitochondria within leaf cells of healthy broad bean had the normal appearance of plant mitochondria, while within cells infected with bean yellow mosaic virus they had matrices that were electron-opaque and cristae that were swollen and angular. However, upon isolation, mitochondria from healthy broad bean cells became indistinguishable from either mitochondria in situ in virus-infected cells, or from mitochondria in vitro isolated from virus-infected cells. Cristae of the isolated mitochondria were greatly inflated, while the matrices were reduced to a thin network in which spherical substructural components, 130–140 A in diameter, were visible. These changes in isolated healthy mitochondria could not be prevented by the use of tannin inhibitors. No significant differences were found in the succinoxidase activities of the isolated healthy and infected mitochondria.

STUDIES ON THE METABOLISM OF LEAVES WITH LOCALIZED VIRUS INFECTIONS: MITOCHONDRIAL ACTIVITY IN TMV-INFECTED NICOTIANA GLUTINOSA L

An increase in the number of mitochondria in leaf tissues of Nicotiana glutinosa soon after inoculation with tobacco mosaic virus was indicated by examination of ultrathin sections, and verified by nitrogen assays of mitochondrial preparations. The succinoxidase activity of mitochondria from locally infected tissues was much higher than that of mitochondria from healthy tissues. Enzyme activity continued at increased levels until the terminal stages of infection, when low succinoxidase activity accompanied degenerative changes in the mitochondria. An early effect of localized virus infection appears to be an increase in the number of mitochondria, and therefore an increase in total enzyme per infected cell. This explains, at least in part, the overall increase in respiration of locally infected tissues previously observed.

OXIDATIVE PHOSPHORYLATION BY PEA SEEDLING MITOCHONDRIA

Using P32in combination with a procedure for quantitative separation of inorganic phosphorus a sensitive method for measuring phosphorylation was devised. It was employed to determine the effects of presoaking seed treatments, and of two inhibitors, 2,4-dinitrophenol (DNP) and malonate, on oxidative phosphorylation by pea seedling mitochondria. The addition of DNP to the reaction mixture resulted in typical uncoupling, but there was an unexpected increase in phosphorylation due to malonate. The length and weight of seedlings presoaked in aerated running water were higher than for those presoaked in standing water; however, mitochondrial preparations from seedlings presoaked in standing water gave higher phosphorylative and oxidative activities. These differences in results were regarded as evidence of 'physiological predetermination'.