Isolation, Molecular Characterization and Expression of Nitrite Reductase Gene from Egyptian Spinach

The nitrite reductase (NiR) gene was isolated, cloned and sequenced from nitrate-induced leaves of the Egyptian Spinacia oleracea seedlings. The sequence of the isolated NiR gene has a 1788 bp open reading frame. The nucleotide sequence of the isolated NiR gene was submitted to the NCBI GenBank database under the accession number MH729808. The deduced protein sequence consisted of 595 amino acid residues with a molecular weight of 66.5 kDa and an isoelectric point of 6.37. The sequence had a 96% homology with the predicted ferredoxin-nitrite reductase sequence, chloroplastic (Spinacia oleracea) and was highly conserved. The highest amino acid percentage belonged to leucine in the predicted NiR protein, which has a higher preference for the α-helix structure. RT-PCR analysis showed that the expression levels of NiR had increased after 2 hrs of potassium nitrate treatment. The NiR protein had a high activity towards NaNO2 substrate after a 3 hr-induction period with potassium nitrate.