title: The critical role of Arabidopsis electron-transfer flavoprotein:ubiquinone oxidoreductase during dark-induced starvation.
abstract: In mammals, electron-transfer flavoprotein:ubiquinone oxidoreductase (ETFQO) and electron-transfer flavoprotein (ETF) are functionally associated, and ETF accepts electrons from at least nine mitochondrial matrix flavoprotein dehydrogenases and transfers them to ubiquinone in the inner mitochondrial membrane. In addition, the mammalian ETF/ETFQO system plays a key role in beta-oxidation of fatty acids and catabolism of amino acids and choline. By contrast, nothing is known of the function of ETF and ETFQO in plants. Sequence analysis of the unique Arabidopsis thaliana homologue of ETFQO revealed high similarity to the mammalian ETFQO protein. Moreover, green fluorescent protein cellular localization experiments suggested a mitochondrial location for this protein. RNA gel blot analysis revealed that Arabidopsis ETFQO transcripts accumulated in long-term dark-treated leaves. Analysis of three independent insertional mutants of Arabidopsis ETFQO revealed a dramatic reduction in their ability to withstand extended darkness, resulting in senescence and death within 10 d after transfer, whereas wild-type plants remained viable for at least 15 d. Metabolite profiling of dark-treated leaves of the wild type and mutants revealed a dramatic decline in sugar levels. In contrast with the wild type, the mutants demonstrated a significant accumulation of several amino acids, an intermediate of Leu catabolism, and, strikingly, high-level accumulation of phytanoyl-CoA. These data demonstrate the involvement of a mitochondrial protein, ETFQO, in the catabolism of Leu and potentially of other amino acids in higher plants and also imply a novel role for this protein in the chlorophyll degradation pathway activated during dark-induced senescence and sugar starvation.
authors.affiliation: Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom.
authors.forename: Kimitsune
authors.initials: K
authors.lastname: Ishizaki
authors.forename: Tony R
authors.initials: TR
authors.lastname: Larson
authors.forename: Nicolas
authors.initials: N
authors.lastname: Schauer
authors.forename: Alisdair R
authors.initials: AR
authors.lastname: Fernie
authors.forename: Ian A
authors.initials: IA
authors.lastname: Graham
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Leaver
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism; D000818:Animals; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002470:Cell Survival; D004269:DNA, Bacterial / Q000378:metabolism; D003624:Darkness; D004579:Electron Transport / Q000502:physiology; D044927:Electron-Transferring Flavoproteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007506:Iron-Sulfur Proteins / Q000235:genetics / Q000378:metabolism*; D007930:Leucine / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology; D008969:Molecular Sequence Data; D009154:Mutation; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D010836:Phytol / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism
chemical_list: D000214:Acyl Coenzyme A; D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; D044927:Electron-Transferring Flavoproteins; D007506:Iron-Sulfur Proteins; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; C036483:T-DNA; D010836:Phytol; D013395:Sucrose; C017447:isovaleryl-coenzyme A; D000587:Oxidoreductases Acting on CH-NH Group Donors; C023120:electron-transferring-flavoprotein dehydrogenase; D007930:Leucine