Regulation of NRT1 and NRT2 gene families of Arabidopsis thaliana: responses to nitrate provision.
Four low-affinity (NRT1), and seven high-affinity (NRT2) nitrate transporter gene homologues have been identified in Arabidopsis thaliana. We investigated the transcript abundances of all eleven genes in shoot and root tissues in response to the provision of 1 mM NO(3)(-), using relative quantitative RT-PCR. Based upon this criterion, genes were classified as nitrate-inducible, nitrate-repressible, or nitrate-constitutive. AtNRT1.1, 2.1, and 2.2 were strongly induced by NO(3)(-), peaking at 3-12 h and subsequently declining. By contrast AtNRT2.4 showed only modest induction both in shoots and roots. Expression of AtNRT2.5, one of the nitrate-repressible genes, was strongly suppressed by nitrate provision in both roots and shoots. The last group, characterized by a constitutive expression pattern, included AtNRT1.2, 1.4, 2.3, 2.6, and 2.7. Correlation coefficients between (13)NO(3)(-) influx from 100 micro M and 5 mM [NO(3)(-)], suggest that high- and low-affinity transport systems are mediated primarily by AtNRT2.1 and AtNRT1.1, respectively. Functional roles for the other members of these families remain uncertain.
Okamoto
Mamoru
M
Department of Botany, University of British Columbia, 6270 University Blvd., Vancouver, V6T 1Z4, Canada.
Vidmar
J John
JJ
Glass
Anthony D M
AD
D000595:Amino Acid Sequence; D027321:Anion Transport Proteins / Q000235:genetics*; D017360:Arabidopsis / Q000187:drug effects* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D000091285:Nitrate Transporters; D009566:Nitrates / Q000494:pharmacology*; D010940:Plant Proteins; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid
D027321:Anion Transport Proteins; D029681:Arabidopsis Proteins; D000091285:Nitrate Transporters; D009566:Nitrates; D010940:Plant Proteins; C101492:NRT1.1 protein, Arabidopsis; C477335:NRT2.1 protein, Arabidopsis