中文摘要：

硝酸盐不仅是植物氮代谢途径中的主要营养成分，也是植物生长发育中的重要信号分子. 硝酸盐的吸收特性和转运机制已成为植物生理学和植物分子生物学领域的研究热点. 本研究从盐生杜氏藻中克隆到一个硝酸盐转运蛋白基因DsNRT2.1-1，通过氨基酸序列比对分析，发现DsNRT2.1-1与24个植物高亲和性硝酸盐转运蛋白（NRT2）序列的同源性高达66%. 在不同浓度硝酸盐诱导下，通过半定量RT-PCR方法分析DsNRT2.1-1基因的表达模式，结果表明DsNRT2.1-1基因在低浓度硝酸盐诱导下表达，而高浓度硝酸盐则抑制其表达. 当外源添加不同浓度的硝酸盐代谢产物NH4＋或天冬氨酸或谷氨酸时，DsNRT2.1-1基因的表达明显受到上述产物的反馈抑制. 在NaCl胁迫条件下，高浓度的NaCl可以诱导DsNRT2.1-1基因的表达. 表达DsNRT2.1-1基因的大肠杆菌在0.69 mol/L NaCl胁迫下表现出对盐的耐受性. 上述研究结果有助于深入研究盐生杜氏藻硝酸盐转运蛋白的作用机理，同时暗示DsNRT2.1-1基因在作物耐盐分子育种中具有一定的应用前景. 图6 参12

英文摘要：

Nitrate is not only a primary nutrient in nitrogen assimilation pathway, but also an important signal for plant development. The mechanism of uptake from the environment and transport of nitrate has been the subject of intensive physiological and molecular studies. A nitrate transporter gene DsNRT2.1-1 was cloned from Dunaliella salina, and its amino acid sequence compared with other 24NRT2 found in NCBI. The expression patterns of DsNRT2.1-1 depending on external nitrate concentration and products of nitrate assimilation were analyzed by semi-quantitative reverse transcriptase-polymerase chain reaction. The results demonstrated that the DsNRT2.1-1 shared 66% similarity to other 24 NRT2. The transcriptional level of DsNRT2.1-1 was strongly induced by low nitrate concentration and repressed by high nitrate concentration. The expression of DsNRT2.1-1 was negatively feedback regulated by products of nitrate assimilation such as ammonium, glutamic acid and aspartic acid. The results also showed that the DsNRT2.1-1 was induced by high NaCl concentration and the Escherichia coli expressing DsNRT2.1-1 acquired resistance to salt stress. The findings are helpful for further study on nitrate uptake and translocation mechanism in D. salina and provide a clue for salt tolerance plant breeding. Fig 6, Ref 12