title: GintAMT1 encodes a functional high-affinity ammonium transporter that is expressed in the extraradical mycelium of Glomus intraradices.
abstract: We report the cloning and characterization of the first NH(4)(+) transporter gene (GintAMT1) in an arbuscular mycorrhizal fungus. GintAMT1 encodes a polypeptide of 479 amino acids sharing high sequence similarity with previously characterized NH(4)(+) transporters from other fungi. Heterologous expression of GintAMT1 in the yeast triple mep mutant complemented the defect of this strain to grow in the presence of less than 1mM NH(4)(+). As revealed by [(14)C]methylammonium uptake experiments carried out in yeast, GintAMT1 encodes a high-affinity NH(4)(+) transporter. In mycelia developed in the presence of 0.9 m M NO(3)(-), GintAMT1 transcription was increased after the addition of 30 microM NH(4)(+) but decreased after the addition of 3 mM NH(4)(+). However, in mycelia grown in the presence of higher N concentrations, GintAMT1 transcripts decreased after the addition of NH(4)(+), irrespective of the concentration used. These data suggest that GintAMT1 is involved in NH(4)(+) uptake by the extraradical mycelia from the surrounding media when it is present at micromolar concentrations.
authors.affiliation: Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, Profesor Albareda 1, 18008 Granada, Spain.
authors.forename: Agustín
authors.initials: A
authors.lastname: López-Pedrosa
authors.forename: Manuel
authors.initials: M
authors.lastname: González-Guerrero
authors.forename: Ascensión
authors.initials: A
authors.lastname: Valderas
authors.forename: Concepción
authors.initials: C
authors.lastname: Azcón-Aguilar
authors.forename: Nuria
authors.initials: N
authors.lastname: Ferrol
mesh_terms: D000595:Amino Acid Sequence; D027682:Cation Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003470:Culture Media; D018552:Daucus carota / Q000382:microbiology*; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005658:Fungi / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D008969:Molecular Sequence Data; D025282:Mycelium / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D038821:Mycorrhizae / Q000254:growth & development* / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D018517:Plant Roots / Q000382:microbiology; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*
chemical_list: D027682:Cation Transport Proteins; D003470:Culture Media; D005656:Fungal Proteins; D000644:Quaternary Ammonium Compounds; D009584:Nitrogen