Effect of Ammonium on Nitrate Uptake by Ihats Transporter in Transgenic Tobacco Plant (Nicotiana Plumbaginifolia Viv.)

The uptake of nitrate is carried out by two transport system, named low affinity transport system (LATS) and high affinity transport system (HATS). The LATS is active in high concentration of nitrate(in mM level) while the HATS usually functions in lower concentration (in µM level). HATS are coded through the gene families of NRT2. Since it has been reported that ammonium has inhibitory effect on Nitrate uptake, in this research, the effect of two concentrations of ammonium(5 and 10 mM) on the rate of nitrate uptake in tobacco transformed plant, Nicotiana plumbaginifolia which it has been transformed using the AtNRT2.1 and AtNRT3.1 genes from the Arabidopsis thaliana plant in hydroponic culture was studied. The existence of the transferred gene was confirmed by PCR and electrophoresis. The results demonstrated that ammonium is able to inhibit the influx of nitrate through the direct inhibition of membrane transporters. However, when the plants were pretreated by ammonium 24 h, nitrate uptake were inhibited completely in both transgenic and wild types with no significant difference. This indicates that probably, inhibition of nitrate uptake affect on both NRT2.1 gene expression and transporter functions.