Fig 1.
Nitrogen uptake and assimilation process in plants.
The uptake of nitrate (NO3-) and ammonium (NH4+) ions is mediated by nitrate (NRT) and ammonium transporters (AMT), respectively. The NO3- entered into the cell is reduced to nitrite ions (NO2-) by an enzyme nitrate reductase (NR). The nitrite ion then moves to plastid and reduced to ammonium ion by nitrite reductase (NiR) enzyme. The ammonium is then incorporated into amino acid by glutamine synthetase and glutamate synthase via GS/GOGAT cycle. The ammonium ion transported by ammonium transporters directly enters into GS/GOGAT cycle. The two additional enzymes glutamate dehydrogenase (GDH) and asparagine synthetase (ASN) also participates in ammonium assimilation. The GS, GDH and ASN are the key enzymes involved in synthesis of glutamine (Gln), Glutamate (Glu) and Asparagine (Asn).
Table 1.
List of proteins along with their molecular weight (M. wt.), isoelectric point (PI), CDS and protein length, subcellular localization and Arabidopsis thaliana orthologs.
Fig 2.
The conserved domain architecture of various proteins involved in nitrate and ammonium uptake, nitrate reduction and ammonia assimilation in B. juncea.
Fig 3.
Bar diagrams showing relative expression of various genes encoding (A) nitrate and (B) ammonium transporters and enzymes involved in (C) nitrate and nitite reduction and (D,E) ammonium assimilation in B. juncea under abiotic stress conditions after 1h (grey bars) and 24h (white bars) as compared to untreated control plants.
Relative expression ratios were determined using qRT-PCR. Asterisks on the top of the bars indicate statistically significant differences (* p-value<0.05 (significant), **p-value < .01(highly significant), ***p < .001 (very highly significant) between 1h and 24h stress treated samples.
Fig 4.
Venn diagram showing genes commonly upregulated and downregulated after 1h and 24h of stress treatments.