中文摘要：

[目的]为揭示萝卜（Raphanus sativus L.）硝酸还原酶基因（RsNR）的分子特征,降低硝酸盐含量,对萝卜RsNR基因进行分离与表达特性研究。[方法]基于本实验室转录组测序所得unigene序列分离RsNR基因cDNA,利用生物信息学方法进行序列分析,采用RT-qPCR方法对不同浓度KNO3（0、5、20、30和50mmol·L^-1）和不同时间（0、4、8、12和24h）处理的萝卜中RsNR基因表达进行检测,并测定硝酸盐含量和硝酸还原酶活性（NRA）。[结果]获得萝卜RsNR基因cDNA序列（GenBank登录号：KM272859）,开放阅读框为2742bp,编码913个氨基酸,RsNR与油菜NR基因（D38219）氨基酸序列相似性为95%。在30mmol·L^-1NO3^--N诱导下,萝卜叶片和根中RsNR基因表达量最高。在30mmol·L^-1NO3^--N诱导初期,叶片和根中RsNR表达量4h达到最大值,随后呈下降趋势;随着硝酸盐处理浓度升高,NRA、硝酸盐含量和RsNR基因表达量均呈先升后降趋势,0～4h内叶片和根中三者均上升,4～24h内NRA和RsNR基因表达下降,而硝酸盐含量呈上升趋势。[结论]NO3^--N可能在转录水平上调控萝卜RsNR基因表达,进而影响其硝酸盐含量和NRA。

英文摘要：

[Objectives]To characterize the nitrate reductase gene and reduce the nitrate content,the isolation and expression profiling of nitrate reductase gene（Rs NR） in radish（Raphanus sativus L.） was conducted.[Methods]Based on the unigene sequence from transcriptome database,the c DNA of Rs NR was isolated.Bioinformatics methods were used for sequence analysis.The expression of Rs NR in radish plants treated with different KNO3 concentrations（0,5,20,30 and 50mmol·L^-1） and time periods（0,4,8,12 and 24h） were detected using RT-q PCR,and the nitrate content and nitrate reductase activity of radish plants were determined.[Results]The c DNA sequence of Rs NR gene was isolated containing an open reading frame（ORF） of 2 742 bp（Gen Bank accession No.： KM272859）.The deduced 913 amino acids sequence showed a 95% identity with NR gene（D38219） in Brassica napus.The maximum Rs NR expression level in leaf and root was induced by 30mmol·L^-1NO3^--N.In a short-term induction of 30 mmol·L^-1NO3^--N,the expression level of Rs NR reached a maximum at 4h in leaf and root,and then decreased steadily.Moreover,the induction kinetics of NRA,nitrate accumulation and Rs NR expression levels were enhanced in a certain value with increasing nitrate concentration,but decreased later.The NRA,nitrate content and the Rs NR expression level showed a increase trend at 0-4h.In contrast,there was a similar decrease trend of NRA and Rs NR expression levels,and a increase trend of nitrate content at 4-24h.[Conclusions]The results indicate that NO3^- may regulate the expression level of NR gene at the transcriptional level,thus affecting the nitrate content and NRA.