Record ID No. |
3772 |
Author(s) |
Pérez-Tienda J, Valderas A, Camañes G, García-Agustín P, Ferrol N. , 2012 |
Affiliation |
Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, Profesor Albareda 1, 18008, Granada, Spain. e-mail: nuria.ferrol@eez.csic.es |
Title |
Kinetics of NH4+uptake by the arbuscular mycorrhizal fungus Rhizophagus irregularis |
Source. Vol.(no):Page |
Mycorrhiza, 22 (6): 485-491p. |
Categories |
Arbuscular Mycorrhiza |
Subjects |
Biochemistry |
Host |
Rhizophagus irregularis |
Organism |
AMF |
Country |
Spain, Europe |
Abstracts |
The kinetics and energetics of (15)NH (4) (+) uptake by the extraradical mycelium of the arbuscular mycorrhizal fungus Rhizophagus irregularis were investigated. (15)NH (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 (15)NH (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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