The cassava grows well on low-nutrient soils because of its high-affinity to absorb nitrate. However, the molecular mechanisms by which cassava adapts itself to this environment remain elusive, although we have cloned a putative gene named MeNRT2.1 which has a crucial role in high-affinity nitrate transporter from cassava seeding. Here, the expression pattern of MeNRT2.1 was further assessed using the GUS activity driven by MeNRT2.1 promoter in Arabidopsis transformation plants. The GUS activity was monitored over time following the reduction of nitrate supply. The GUS gene expression not only peaked in roots after 12 h in 0.2mM nitrate media, but also stained stems and leaves. Arabidopsis plants with overexpression of MeNRT2.1 increased the biomass compared to the wild type on rich nitrogen (N-full) media. However, chlorate sensitivity analysis showed that Arabidopsis plants expressing MeNRT2.1 were more susceptable to chlorate than wild type. Significantly, after growing for 15 days on media containing 0.2mM nitrate concentration, wild-type plants became yellowor died, while the transgenic MeNRT2.1 Arabidopsis plants maintained normal growth. With significant increases in the amount of 15NO- 3 uptake in roots, the MeNRT2.1 plants also increased the contents of chlorophyll and nitrate reductase. Taken together, these results demonstrate that MeNRT2.1 has an important role in adaptation to low nitrate concentration as a nitrate transporter.

中文翻译：

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木薯硝酸盐转运蛋白NRT2.1的表达使得拟南芥对硝酸盐的耐受性低。

木薯由于吸收硝酸盐的亲和力高，因此在低营养的土壤上生长良好。然而，尽管我们已经克隆了一个名为MeNRT2.1的推定基因，该基因在木薯播种的高亲和力硝酸盐转运蛋白中具有至关重要的作用，但是木薯适应这种环境的分子机制仍然难以捉摸。在这里，使用拟南芥转化植物中由MeNRT2.1启动子驱动的GUS活性进一步评估了MeNRT2.1的表达模式。硝酸盐供应减少后，随时间监测GUS活性。GUS基因表达不仅在0.2mM硝酸盐培养基中12 h后在根中达到高峰，而且茎和叶染色。与MeNRT2.1过量表达的拟南芥植物相比，在富氮（N-full）培养基上的野生生物与野生型相比具有更高的生物量。然而，氯酸盐敏感性分析表明，表达MeNRT2.1的拟南芥植物比野生型对氯酸盐的敏感性更高。值得注意的是，在含0.2mM硝酸盐的培养基上生长15天后，野生型植物变黄或死亡，而转基因MeNRT2.1拟南芥植物保持正常生长。随着根部15NO-3吸收量的显着增加，MeNRT2.1植物还增加了叶绿素和硝酸盐还原酶的含量。综上，这些结果表明，MeNRT2.1在适应低硝酸盐浓度方面作为硝酸盐转运蛋白具有重要作用。野生型植物变黄或死亡，而转基因MeNRT2.1拟南芥植物保持正常生长。随着根部15NO-3吸收量的显着增加，MeNRT2.1植物还增加了叶绿素和硝酸盐还原酶的含量。综上，这些结果表明，MeNRT2.1在适应低硝酸盐浓度方面作为硝酸盐转运蛋白具有重要作用。野生型植物变黄或死亡，而转基因MeNRT2.1拟南芥植物保持正常生长。随着根部15NO-3吸收量的显着增加，MeNRT2.1植物还增加了叶绿素和硝酸盐还原酶的含量。综上，这些结果表明，MeNRT2.1在适应低硝酸盐浓度方面作为硝酸盐转运蛋白具有重要作用。