title: The alternative respiratory pathway mediates carboxylate synthesis in white lupin cluster roots under phosphorus deprivation.
abstract: Plant adaptations associated with a high efficiency of phosphorus (P) acquisition can be used to increase productivity and sustainability in a world with a growing population and decreasing rock phosphate reserves. White lupin (Lupinus albus) produces cluster roots that release carboxylates to efficiently mobilize P from P-sorbing soils. It has been hypothesized that an increase in the activity of the alternative oxidase (AOX) would allow for the mitochondrial oxidation of NAD(P)H produced during citrate synthesis in cluster roots at a developmental stage when there is a low demand for ATP. We used the oxygen-isotope fractionation technique to study the in vivo respiratory activities of the cytochrome oxidase pathway (COP) and the alternative oxidase pathway (AOP) in different root sections of white lupins grown hydroponically with and without P. In parallel, AOX protein levels and internal carboxylate concentrations were determined in cluster and non-cluster roots. Higher in vivo AOP activity was measured in cluster roots when malate and citrate concentrations were also high, thus confirming our hypothesis. AOX protein levels were not always correlated with in vivo AOP activity, suggesting post-translational regulation of AOX.
authors.affiliation: Grup de Recerca en Biologia de les Plantes en Condicions Mediterranies, Departament de Biologia, Universitat de les Illes Balears, Carretera de Valldemossa Km 7.5, 07122, Palma de Mallorca, Spain.
authors.forename: Igor
authors.initials: I
authors.lastname: Florez-Sarasa
authors.forename: Hans
authors.initials: H
authors.lastname: Lambers
authors.forename: Xing
authors.initials: X
authors.lastname: Wang
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Finnegan
authors.forename: Miquel
authors.initials: M
authors.lastname: Ribas-Carbo
mesh_terms: D002264:Carboxylic Acids / Q000378:metabolism*; D019069:Cell Respiration / Q000187:drug effects; D004583:Electrons; D031297:Lupinus / Q000166:cytology* / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism*; D010710:Phosphates / Q000494:pharmacology; D010758:Phosphorus / Q000172:deficiency*; D010940:Plant Proteins / Q000378:metabolism*; D018517:Plant Roots / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D000099188:Alternative Oxidase
chemical_list: D002264:Carboxylic Acids; D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010710:Phosphates; D010758:Phosphorus; D010940:Plant Proteins; D000099188:Alternative Oxidase
keywords: alternative oxidase; oxygen-isotope fractionation; phosphorous deficiency; root exudation