关键词: 白菜, 硝酸盐, NRT2, 实时定量PCR, 亚细胞定位

Abstract: In this study，a full-length of cDNA sequence of a high-affinity nitrate transporter gene BcNRT2 was cloned from non-heading Chinese cabbage（Brassica campestris ssp. chinensis Makino）cultivar‘Suzhouqing’using reverse transcript PCR（RT-PCR）. Sequence analysis showed that the length of nucleotide sequence of this gene is 1 593 bp，containing a complete open reading frame to encode 530 amino acids. Nucleotide and amino acid sequence comparison indicates that BcNRT2 has a certain high similarity with the orthologous gene BnNRT2 in Brassica napus（98%，99%）and AtNRT2.1 in Arabidopsis thaliana（90%，95%），respectively. Conclusion was made that NRT2 gene is highly conserved among several plant species. Quantitative real-time PCR analysis showed that the expression of BcNRT2 has the highest level in root cells，and expression pattern of this gene belongs to induced system. After 0.5 h treatment of low concentrations of NO3-（0.2 mmol · L-1 KNO3），the expression of BcNRT2 was up-regulated rapidly in root and shoot，suggested that BcNRT2 may acts as a NO3- sensor or signal transducer. After treatment of high concentrations of NO3-（20 mmol · L-1 KNO3），the expression of BcNRT2 was highly up-regulated and lasted longer in root and shoot，which may be resulted from a high-level response of the regulation of a low-affinity nitrate transporter NRT1.1. BcNRT2 protein was located at the plasma membrane supported by subcellular localization assays experiment.

Key words: non-heading Chinese cabbage, nitrate, NRT2, real-time RT-PCR, subcellular localization