Kinetics of NH 4 + uptake by the arbuscular mycorrhizal fungus Rhizophagus irregularis
Scholar | Otros documentos del autor: Pérez-Tienda, J.; Valderas, A.; Camañes Querol, Gemma; García Agustín, Pilar; Ferrol, N.
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TítuloKinetics of NH 4 + uptake by the arbuscular mycorrhizal fungus Rhizophagus irregularis
Fecha de publicación2012-08
The kinetics and energetics of 15NH 4 + uptake by the extraradical mycelium of the arbuscular mycorrhizal fungus Rhizophagus irregularis were investigated. 15NH 4 + uptake increased with increasing substrate concent ... [+]
The kinetics and energetics of 15NH 4 + uptake by the extraradical mycelium of the arbuscular mycorrhizal fungus Rhizophagus irregularis were investigated. 15NH 4 + uptake increased with increasing substrate concentration over the concentration range of 0.002 to 25 mM. Eadie–Hofstee plots showed that ammonium (NH 4 + ) uptake over this range was biphasic. At concentrations below 100 μM, NH 4 + uptake fits a Michaelis–Menten curve, typical of the activity of a saturable high-affinity transport system (HATS). At concentrations above 1 mM, NH 4 + influx showed a linear response typical of a nonsaturable low-affinity transport system (LATS). Both transport systems were dependent on external pH. The HATS and, to a lesser extent, the LATS were inhibited by the ionophore carbonylcyanide m-chlorophenylhydrazone (CCCP) and the ATP-synthesis inhibitor 2,4-dinitrophenol. These data indicate that the two NH 4 + transport systems of R. irregularis are dependent on metabolic energy and on the electrochemical H+ gradient. The HATS- and the LATS-mediated 15NH 4 + influxes were also regulated by acetate. This first report of the existence of active high- and low-affinity NH4+ transport systems in the extraradical mycelium of an arbuscular mycorrhizal fungus and provides novel information on the mechanisms underlying mycosymbiont uptake of nitrogen from the soil environment. [-]
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Cita bibliográficaPérez-Tienda, J., Valderas, A., Camañes, G., García-Agustín, P., & Ferrol, N. (2012). Kinetics of NH 4+ uptake by the arbuscular mycorrhizal fungus Rhizophagus irregularis. Mycorrhiza, 22(6), 485-491.
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