title: Nitrate reductase activity is required for nitrate uptake into fungal but not plant cells.
abstract: The ability to transport net nitrate was conferred upon transformant cells of the non-nitrate-assimilating yeast Pichia pastoris after the introduction of two genes, one encoding nitrate reductase and the other nitrate transport. It was observed that cells of this lower eukaryote transformed with the nitrate transporter gene alone failed to display net nitrate transport despite having the ability to produce the protein. In addition, loss-of-function nitrate reductase mutants isolated from several nitrate-assimilating fungi appeared to be unable to accumulate nitrate. Uptake assays using the tracer (13)NO(3)(-) showed that nitrate influx is negligible in cells of a nitrate reductase null mutant. In parallel studies using a higher eukaryotic plant, Arabidopsis thaliana, loss-of-function nitrate reductase strains homozygous for both NIA1 insertion and NIA2 deletion were found to have no detectable nitrate reductase mRNA or nitrate reductase activity but retained the ability to transport nitrate. The reasons for these fundamental differences in nitrate transport into the cells of representative members of these two eukaryotic kingdoms are discussed.
authors.affiliation: School of Biology, University of St. Andrews, St. Andrews KY16 9TH, Scotland, United Kingdom.
authors.forename: Shiela E
authors.initials: SE
authors.lastname: Unkles
authors.forename: Rongchen
authors.initials: R
authors.lastname: Wang
authors.forename: Ye
authors.initials: Y
authors.lastname: Wang
authors.forename: Anthony D M
authors.initials: AD
authors.lastname: Glass
authors.forename: Nigel M
authors.initials: NM
authors.lastname: Crawford
authors.forename: James R
authors.initials: JR
authors.lastname: Kinghorn
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D001233:Aspergillus nidulans / Q000378:metabolism; D015153:Blotting, Western; D002455:Cell Division; D002704:Chlorates / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D005658:Fungi / Q000378:metabolism; D017353:Gene Deletion; D006720:Homozygote; D009154:Mutation; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000378:metabolism*; D009566:Nitrates / Q000737:chemistry / Q000493:pharmacokinetics*; D009569:Nitric Oxide / Q000378:metabolism; D010843:Pichia / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D013997:Time Factors
chemical_list: D002704:Chlorates; D018076:DNA, Complementary; D009566:Nitrates; D012333:RNA, Messenger; D011994:Recombinant Proteins; D009569:Nitric Oxide; D009565:Nitrate Reductases; D050901:Nitrate Reductase