The Regulatory Region Controlling the Nitrate-Responsive Expression of a Nitrate Reductase Gene, NIA1, in Arabidopsis
The Regulatory Region Controlling the Nitrate-Responsive Expression of a Nitrate Reductase Gene, NIA1, in Arabidopsis
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DOI：
10.1093/pcp/pcr033
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发表时间：
2011-05-01
影响因子：
4.9
通讯作者：
Yanagisawa, Shuichi
中科院分区：
文献类型：
--
作者：
Konishi, Mineko;Yanagisawa, Shuichi
硝酸还原酶（NR）是催化硝酸盐同化的第一步的酶。众所周知，硝酸盐在各种植物中迅速诱导NR基因的表达。以前，据报道，烟草NR基因启动子的活性在含有铵作为唯一氮源的培养基上生长的烟草植物中高，但在含有硝酸盐的培养基上生长的烟草植物中低。这对NR基因启动子在硝酸盐诱导表达中的作用提出了质疑。此外，在以前的研究中，转化含有NR位点的基因组片段在有限的程度上恢复了NR突变体中降低的NR活性，这表明NR基因表达的复杂调控。在这里，我们表明，虽然在拟南芥，NIA 1，NR基因的1.9 kb的启动子，不激活硝酸盐，GUS（β-葡萄糖醛酸酶）报告基因之间插入的NIA 1编码区的5 '-和3'-侧翼序列的表达强烈诱导硝酸盐。当3 '-侧翼序列在35 S最小启动子的控制下融合到GUS基因的下游时，其表达也被硝酸盐强烈诱导。此外，对3 '侧翼区的解剖分析显示，转录终止子下游的序列而不是3'非翻译区在硝酸盐诱导型表达中起作用，表明NIA 1的硝酸盐诱导型转录需要3 '侧翼序列。我们还表明，2.7 kb的启动子序列NIA 2，另一个NR基因的拟南芥，不能直接硝酸盐诱导的表达。
Nitrate reductase (NR) is the enzyme that catalyzes the first step of nitrate assimilation. It is well known that the expression of NR genes is rapidly induced in various plants by nitrate. Previously, the activity of a tobacco NR gene promoter was reported to be high in tobacco plants grown on medium containing ammonium as the sole nitrogen source, but low in tobacco plants grown on nitrate-containing medium. This cast some doubt on the role of the NR gene promoter in the nitrate-inducible expression of this gene. Furthermore, in previous studies, transformation with genomic fragments containing NR loci restored the reduced NR activity in NR mutants to a limited extent, suggesting a complex regulation of NR gene expression. Here, we show that although the 1.9 kb promoter of an NR gene in Arabidopsis, NIA1, is not activated by nitrate, the expression of a GUS (beta-glucuronidase) reporter gene inserted between the 5'- and 3'-flanking sequences of the NIA1 coding region is strongly induced by nitrate. When the 3'-flanking sequence was fused downstream of the GUS gene under the control of the 35S minimal promoter, its expression was also strongly induced by nitrate. Furthermore, dissection analysis of the 3'-flanking region revealed that the sequence downstream of the transcriptional terminator rather than the 3'-untranslated region plays a role in nitrate-inducible expression, indicating a requirement for the 3'-flanking sequence for the nitrate-inducible transcription of NIA1. We also show that the 2.7 kb promoter sequence of NIA2, another NR gene of Arabidopsis, cannot direct nitrate-inducible expression.