title: Changes of alternative oxidase activity, capacity and protein content in leaves of Cucumis sativus wild-type and MSC16 mutant grown under different light intensities.
abstract: In vitro studies demonstrated that alternative oxidase (AOX) is biochemically regulated by a sulfhydryl-disulfide system, interaction with alpha-ketoacids, ubiquinone pool redox state and protein content among others. However, there is still scarce information about the in vivo regulation of the AOX. Cucumis sativus wild-type (WT) and MSC16 mutant plants were grown under two different light intensities and were used to analyze the relationship between the amount of leaf AOX protein and its in vivo capacity and activity at night and day periods. WT and MSC16 plants presented lower total respiration (V(t)), cytochrome oxidase pathway (COP) activity (v(cyt)) and alternative oxidase pathway (AOP) activity (v(alt)) when grown at low light (LL), although growth light intensity did not change the amount of cytochrome oxidase (COX) nor AOX protein. Changes of v(cyt) related to growing light conditions suggested a substrate availability and energy demand control. On the other hand, the total amount of AOX protein present in the tissue does not play a role in the regulation neither of the capacity nor of the activity of the AOP in vivo. Soluble carbohydrates were directly related to the activity of the AOP. However, although differences in soluble sugar contents mostly regulate the capacity of the AOP at different growth light intensities, additional regulatory mechanisms are necessary to fully explain the observed results.
authors.affiliation: Grup de Recerca en Biologia de les Plantes en Condicions Mediterranies, Departament de Biologï a, Universitat de les Illes Balears, Ctra. Valldemossa Km. 7.5, 07122 Palma de Mallorca, Spain.
authors.forename: Igor
authors.initials: I
authors.lastname: Florez-Sarasa
authors.forename: Monika
authors.initials: M
authors.lastname: Ostaszewska
authors.forename: Alexander
authors.initials: A
authors.lastname: Galle
authors.forename: Jaume
authors.initials: J
authors.lastname: Flexas
authors.forename: Anna M
authors.initials: AM
authors.lastname: Rychter
authors.forename: Miquel
authors.initials: M
authors.lastname: Ribas-Carbo
mesh_terms: D000704:Analysis of Variance; D015153:Blotting, Western; D050260:Carbohydrate Metabolism / Q000528:radiation effects; D019069:Cell Respiration / Q000528:radiation effects; D002940:Circadian Rhythm / Q000528:radiation effects; D018553:Cucumis sativus / Q000166:cytology / Q000201:enzymology* / Q000254:growth & development / Q000528:radiation effects*; D003624:Darkness; D003576:Electron Transport Complex IV / Q000378:metabolism; D004583:Electrons; D008027:Light; D024101:Mitochondrial Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D010088:Oxidoreductases / Q000378:metabolism*; D018515:Plant Leaves / Q000201:enzymology* / Q000254:growth & development / Q000528:radiation effects; D010940:Plant Proteins / Q000378:metabolism*; D012995:Solubility / Q000528:radiation effects; D000099188:Alternative Oxidase
chemical_list: D003576:Electron Transport Complex IV; D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D000099188:Alternative Oxidase