Expression studies of Nrt2:1Np, a putative high-affinity nitrate transporter:: evidence for its role in nitrate uptake
Expression studies of Nrt2:1Np, a putative high-affinity nitrate transporter:: evidence for its role in nitrate uptake
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DOI：
10.1046/j.1365-313x.1998.00181.x
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发表时间：
1998-06-01
期刊：
影响因子：
7.2
通讯作者：
Daniel-Vedele, F
中科院分区：
文献类型：
--
作者：
Krapp, A;Fraisier, V;Daniel-Vedele, F
研究了白花烟草高亲和力硝酸盐转运蛋白基因Nrt2Np在不同生理条件下的表达。Nrt2Np被很低的硝酸盐浓度快速诱导，并被还原的氮代谢产物抑制。此外，Nrt2Np与参与硝酸盐同化的其他基因(Nia、Nii)协同表达。硝酸还原酶活性的缺乏，伴随着体内高硝酸盐浓度和低水平的氮代谢产物，如谷氨酰胺，导致Nrt2Np的过度表达，表明高硝酸盐浓度本身并不抑制Nrt2Np的表达。通过对硝酸盐吸收特性改变的植物的研究，我们发现了Nrt2 mRNA的积累与15N硝酸盐内流速率之间的相关性，首次提供了Nrt2的表达与硝酸盐吸收速率相关的证据。原位杂交显示了一种组织特异性表达模式。Nrt2Np基因的积累分布于根尖的各层，其中以表皮和内胚层细胞的积累最高。而在成熟根组织中，Nrt2主要在侧根原基和表皮中表达。
Expression of the gene Nrt2Np, which encodes a putative high-affinity nitrate transporter of Nicotiana plumbaginifolia was studied under variable physiological conditions. Nrt2Np is rapidly induced by very low nitrate concentrations and repressed by reduced nitrogen metabolites. Furthermore, Nrt2Np is expressed in coordination with other genes involved in nitrate assimilation (Nia, Nii). A deficiency in nitrate reductase activity, which is accompanied by high internal nitrate concentration and low levels of nitrogen metabolites, e.g, glutamine, leads to an overexpression of Nrt2Np, showing that high nitrate concentration per se does not repress Nrt2Np expression. By investigating plants with altered nitrate uptake properties, we showed a correlation between Nrt2 mRNA accumulation and 15N nitrate influx rates, providing the first evidence that the expression of Nrt2 correlates with the rate of nitrate uptake. In situ hybridization revealed a tissue-specific expression pattern. Nrt2Np mRNA accumulation is localized throughout all layers of the root tip, being highest in epidermal and endodermal cells. However, in mature root tissue, Nrt2 expression was detected mainly in the lateral root primordia and in the epidermis.