alternative respiratory pathway mediates carboxylate synthesis in white lupin cluster roots under phosphorus deprivation

• Published in: Plant, cell and environment Vol. 37; no. 4; pp. 922 - 928
• Main Authors: FLOREZ‐SARASA, IGOR, LAMBERS, HANS, WANG, XING, FINNEGAN, PATRICK M, RIBAS‐CARBO, MIQUEL
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell 01.04.2014; Wiley Subscription Services, Inc
• Subjects: adenosine triphosphate; alternative oxidase; Biological and medical sciences; Carboxylic Acids - metabolism; Cell Respiration - drug effects; citrates; cytochrome-c oxidase; Electrons; fractionation; Fundamental and applied biological sciences. Psychology; in vivo studies; Lupinus - cytology; Lupinus - enzymology; Lupinus - growth & development; Lupinus - metabolism; Lupinus albus; Mitochondria - drug effects; Mitochondria - metabolism; Mitochondrial Proteins - metabolism; NAD (coenzyme); oxidation; Oxidoreductases - metabolism; oxygen‐isotope fractionation; Phosphates - pharmacology; phosphorous deficiency; phosphorus; Phosphorus - deficiency; plant adaptation; Plant Proteins - metabolism; Plant Roots - cytology; Plant Roots - drug effects; Plant Roots - enzymology; Plant Roots - metabolism; rock phosphate; root exudation; roots; phosphorous deficiency; Deprivation; oxygen-isotope fractionation; Enzyme; Oxidase; Plant ecology; Phosphorus; Oxygen isotopes; cluster root; Leguminosae; root exudation; Dicotyledones; Angiospermae; Carboxylate; Isotopic fractionation; Lupinus albus; Spermatophyta; Exudation; Cyanide resistant respiration; Oxidoreductases; Fodder crop; alternative oxidase
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.12208

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.