关键词: 白菜, 亚硝酸还原酶, 克隆, 基因表达

Abstract: The BcNiR gene was cloned using RT-PCR and 3′/5′RACE techniques with cDNA isolated from non-heading Chinese cabbage [Brassica campestris L. ssp. chinensis (L. ) Makino ] , which was nitrateinduced for 4 hours. The cDNA of BcNiR was 1 852 bp containing a 1 749 bp opening reading frame (ORF)
encoding 583 amino acids. Further comparison showed that BcNiR had high homology to A rabidopsis thaliana NiR1 gene and Nicotiana tabacum nii gene, were 83% and 76% , respectively. The predicted BcNiR protein was found to have a hemoprotein beta-compnent ( ferrodoxin-like) , a siroheme-binding site and 4Fe2-4S region. A similar 3D structural were obtained from the SW iSS-MODEL database. Real-time PCR analysis showed that, the expressions of BcNiR were awfully higher in leaves than that in roots. Furthermore, in nitrate
treatment experiments, both the maximum expressions of BcNiR in roots and leaves were induced by 30 mmol·L ^{- 1} NO₃^- - N at 4 h. 5 and 10 mmol·L ^{- 1}NH4⁺ - N treatments indicated that high level of NH4⁺ -N treatment restrained the expression of ^BcNiR.

Key words: Brassica campestris L. ssp. chinensis (L. ) Makino, NiR gene, cDNA, cloning, exp ression