Regulation of the nitrate transporter gene AtNRT2.1 in Arabidopsis thaliana: responses to nitrate, amino acids and developmental stage.
The NR72.1 gene codes for a high-affinity nitrate transporter in Arabidopsis thaliana. To examine the regulation of NRT2.1 gene expression, we used a promoter-beta-glucuronidase (GUS) fusion and found that the NRT2.1 promoter directs expression to the epidermal, cortical and endodermal cell layers of mature root parts. The gene appeared to be expressed essentially in roots, but was also present in the leaf hydathodes. Investigation of NRT2.1 expression pattern during the plant developmental cycle showed that it increased rapidly during early vegetative growth, peaked prior to floral stem emergence, and decreased to very low levels in flowering and silique-bearing plants. Experiments with various nitrogen supply regimes demonstrated the induction of NRT2.1 expression by nitrate and repression by amino acids. Amino acid analysis showed that this repression was specifically related to increased internal glutamine, suggesting a role for this particular amino acid in nitrogen signalling responsible for nitrate uptake regulation. Taken together, our results support the hypothesis that the NRT2.1 gene codes for a major component of the inducible high-affinity transport system for nitrate, which is spatially and developmentally controlled at the transcriptional level. Surprisingly, NRT2.1 was not expressed in younger root parts, although a similar rate of nitrate influx was observed in both young and old root samples. This lack of correlation between nitrate influx and NRT2.1 expression suggests that another high-affinity nitrate transporter operates in root tips.
Nazoa
Patricia
P
Biochimie & Physiologie Moléculaire des Plantes, UMR 5004 INRA/CNRS/Agro-M/UM-2, Place Viala, 34060 Montpellier cedex 1, France.
Vidmar
J John
JJ
Tranbarger
Timothy J
TJ
Mouline
Karine
K
Damiani
Isabelle
I
Tillard
Pascal
P
Zhuo
Degen
D
Glass
Anthony D M
AD
Touraine
Bruno
B
D000596:Amino Acids / Q000494:pharmacology; D027321:Anion Transport Proteins / Q000235:genetics* / Q000378:metabolism; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D015152:Blotting, Northern; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005966:Glucuronidase / Q000235:genetics / Q000378:metabolism; D000091285:Nitrate Transporters; D009566:Nitrates / Q000378:metabolism / Q000494:pharmacology; D010940:Plant Proteins; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
D000596:Amino Acids; D027321:Anion Transport Proteins; D029681:Arabidopsis Proteins; D005966:Glucuronidase; D000091285:Nitrate Transporters; D009566:Nitrates; D010940:Plant Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; C477335:NRT2.1 protein, Arabidopsis