title: Nitrite reduction and superoxide-dependent nitric oxide degradation by Arabidopsis mitochondria: influence of external NAD(P)H dehydrogenases and alternative oxidase in the control of nitric oxide levels.
abstract: Mitochondria recently have emerged as important sites in controlling NO levels within the cell. In this study, the synthesis of nitric oxide (NO) from nitrite and its degradation by mitochondria isolated from Arabidopsis thaliana were examined. Oxygen and NO concentrations in the reaction medium were measured with specific electrodes. Nitrite inhibited the respiration of isolated A. thaliana mitochondria, in competition with oxygen, an effect that was abolished or potentiated when electron flow occurred via alternative oxidase (AOX) or cytochrome c oxidase (COX), respectively. The production of NO from nitrite was detected electrochemically only under anaerobiosis because of a superoxide-dependent process of NO degradation. Electron leakage from external NAD(P)H dehydrogenases contributed the most to NO degradation as higher rates of Amplex Red-detected H(2)O(2) production and NO consumption were observed in NAD(P)H-energized mitochondria. Conversely, the NO-insensitive AOX diminished electron leakage from the respiratory chain, allowing the increase of NO half-life without interrupting oxygen consumption. These results show that the accumulation of nitric oxide derived from nitrite reduction and the superoxide-dependent mechanism of NO degradation in isolated A. thaliana mitochondria are influenced by the external NAD(P)H dehydrogenases and AOX, revealing a role for these alternative proteins of the mitochondrial respiratory chain in the control of NO levels in plant cells.
authors: Departamento de Biologia Vegetal, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), CP 6109, Campinas, SP, 13083-970, Brazil.
authors: Alfredo
authors: A
authors: Wulff
authors: Halley Caixeta
authors: HC
authors: Oliveira
authors: Elzira Elisabeth
authors: EE
authors: Saviani
authors: Ione
authors: I
authors: Salgado
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism; D003627:Data Interpretation, Statistical; D014450:Electron Transport Complex III / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins; D009243:NAD / Q000378:metabolism; D009245:NADH Dehydrogenase / Q000378:metabolism* / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010940:Plant Proteins; D013481:Superoxides / Q000378:metabolism*; D000099188:Alternative Oxidase
chemical_list: D029681:Arabidopsis Proteins; D014450:Electron Transport Complex III; D003576:Electron Transport Complex IV; D024101:Mitochondrial Proteins; D009243:NAD; D009245:NADH Dehydrogenase; D009569:Nitric Oxide; D009573:Nitrites; D010088:Oxidoreductases; D010100:Oxygen; D010940:Plant Proteins; D013481:Superoxides; D000099188:Alternative Oxidase