title: Characterisation and expression analysis of a nitrate transporter and nitrite reductase genes, two members of a gene cluster for nitrate assimilation from the symbiotic basidiomycete Hebeloma cylindrosporum.
abstract: Symbiotic ectomycorrhizal fungi contribute to the nitrogen nutrition of their host-plants but little information is available on the molecular control of their nitrogen metabolism. We cloned and characterised genes encoding a nitrite reductase and a nitrate transporter in the ectomycorrhizal basidiomycete Hebeloma cylindrosporum. These two genes are divergently transcribed and linked to a previously cloned nitrate reductase gene, thus demonstrating that nitrate assimilation gene clusters occur in homobasidiomycetes. The nitrate transporter polypeptide (NRT2) is characterised by 12 transmembrane domains and presents both a long putative intracellular loop and a short C-terminal tail, two structural features which distinguish fungal high-affinity transporters from their plant homologues. In different wild-type genetic backgrounds, transcription of the two genes was repressed by ammonium and was strongly stimulated not only in the presence of nitrate but also in the presence of organic nitrogen sources or under nitrogen deficiency.
authors.affiliation: Laboratoire d'Ecologie Microbienne, UMR CNRS 5557, Université Claude Bernard Lyon 1, Bât. A. Lwoff, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne, France.
authors.forename: Patricia
authors.initials: P
authors.lastname: Jargeat
authors.forename: David
authors.initials: D
authors.lastname: Rekangalt
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Verner
authors.forename: Gilles
authors.initials: G
authors.lastname: Gay
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Debaud
authors.forename: Roland
authors.initials: R
authors.lastname: Marmeisse
authors.forename: Laurence
authors.initials: L
authors.lastname: Fraissinet-Tachet
mesh_terms: D027321:Anion Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D001487:Basidiomycota / Q000235:genetics*; D001693:Biological Transport, Active; D015152:Blotting, Northern; D015139:Blotting, Southern; D040461:Gene Components; D005786:Gene Expression Regulation; D008969:Molecular Sequence Data; D000091285:Nitrate Transporters; D009566:Nitrates / Q000378:metabolism; D009572:Nitrite Reductases / Q000235:genetics*; D010940:Plant Proteins; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D020871:RNA Stability; D017422:Sequence Analysis, DNA
chemical_list: D027321:Anion Transport Proteins; D000091285:Nitrate Transporters; D009566:Nitrates; D010940:Plant Proteins; D000644:Quaternary Ammonium Compounds; D009572:Nitrite Reductases