Nitrite reductase (NiR) is a critical enzyme involved in nitrogen metabolism in plants. A full-length cDNA sequence of 1,764 bp for the NiR gene was isolated from mulberry (Morus L.) using reverse transcription polymerase chain reaction (RT-PCR). This NiR cDNA encodes a protein of 587 amino acids with a theoretical molecular weight of 65.4 kDa. The predicted Morus alba NiR (MaNiR) protein includes a repeated hemoprotein ferredoxin-like beta-component together with a 4Fe-4S-binding domain and a siroheme-binding site, which could be expressed in a recombinant prokaryotic expression system. Nitrite reductase activity was exhibited only when both of the repeat functional domains were expressed together. Both glutam... More
Nitrite reductase (NiR) is a critical enzyme involved in nitrogen metabolism in plants. A full-length cDNA sequence of 1,764 bp for the NiR gene was isolated from mulberry (Morus L.) using reverse transcription polymerase chain reaction (RT-PCR). This NiR cDNA encodes a protein of 587 amino acids with a theoretical molecular weight of 65.4 kDa. The predicted Morus alba NiR (MaNiR) protein includes a repeated hemoprotein ferredoxin-like beta-component together with a 4Fe-4S-binding domain and a siroheme-binding site, which could be expressed in a recombinant prokaryotic expression system. Nitrite reductase activity was exhibited only when both of the repeat functional domains were expressed together. Both glutamic acid and gibberellins promoted MaNiR expression in mulberry leaves, but inhibited its expression in roots and stems. Following dedifferentiation of mulberry hypocotyls and cotyledons, MaNiR expression decreased strongly. This suggests that NiR could play an important role in the in vitro regeneration of mulberry hypocotyls and cotyledons.
