title: A 150 kDa plasma membrane complex of AtNRT2.5 and AtNAR2.1 is the major contributor to constitutive high-affinity nitrate influx in Arabidopsis thaliana.
abstract: In plants that have been deprived of nitrate for a significant length of time, a constitutive high-affinity nitrate transport system (cHATS) is responsible for initial nitrate uptake. This absorbed nitrate leads to the induction of the major nitrate transporters and enzymes involved in nitrate assimilation. By use of (13) NO3 (-) influx measurements and Blue Native polyacrylamide gel electrophoresis we examined the role of AtNRT2.5 in cHATS in wild type (WT) and various T-DNA mutants of Arabidopsis thaliana. We demonstrate that AtNRT2.5 is predominantly expressed in roots of nitrate-deprived WT plants as a 150 kDa molecular complex with AtNAR2.1. This complex represents the major contributor to cHATS influx, which is reduced by 63% compared with WT in roots of Atnrt2.5 mutants. The remaining cHATS nitrate influx in these mutants is due to a residual contribution by the inducible high-affinity transporter encoded by AtNRT2.1/AtNAR2.1. Estimates of the kinetic properties of the NRT2.5 transporter reveal that its low Km for nitrate makes this transporter ideally suited to detect and respond to trace quantities of nitrate in the root environment.
authors.affiliation: Department of Botany, University of British Columbia, 6270 University Blvd, Vancouver, British Columbia, V6T 1Z4, Canada.
authors.forename: Zorica
authors.initials: Z
authors.lastname: Kotur
authors.affiliation: Department of Botany, University of British Columbia, 6270 University Blvd, Vancouver, British Columbia, V6T 1Z4, Canada.
authors.forename: Anthony D M
authors.initials: AD
authors.lastname: Glass
mesh_terms: D027321:Anion Transport Proteins / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D018527:Hydroponics; D016013:Likelihood Functions; D008970:Molecular Weight; D016254:Mutagenesis, Insertional / Q000235:genetics; D009154:Mutation; D063347:Native Polyacrylamide Gel Electrophoresis; D009566:Nitrates / Q000378:metabolism*; D009587:Nitrogen Isotopes; D010641:Phenotype; D010802:Phylogeny; D018517:Plant Roots / Q000378:metabolism; D018520:Plant Shoots / Q000378:metabolism
chemical_list: D027321:Anion Transport Proteins; D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; C516470:NAR2.1 protein, Arabidopsis; C583321:NRT2.5 protein, Arabidopsis; D009566:Nitrates; D009587:Nitrogen Isotopes; C036483:T-DNA
keywords: NAR2.1; NRT2.5; high-affinity nitrate transport; inducible