Sequence homology requirements for transcriptional silencing of 35S transgenes and post-transcriptional silencing of nitrite reductase (trans)genes by the tobacco 271 locus
Sequence homology requirements for transcriptional silencing of 35S transgenes and post-transcriptional silencing of nitrite reductase (trans)genes by the tobacco 271 locus
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烟草 271 位点 35S 转基因转录沉默和亚硝酸还原酶（反式）基因转录后沉默的序列同源性要求
DOI：
10.1007/bf00041391
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发表时间：
1996
影响因子：
5.1
通讯作者：
H. Vaucheret
中科院分区：
文献类型：
--
作者：
D. Thierry;H. Vaucheret
烟草植物271的转基因位点（271位点）位于端粒上，由携带由花椰菜花叶病毒（CaMV）19S启动子驱动的NptII标记基因的质粒和在CaMV 35S启动子控制下以反义方向克隆的叶特异性亚硝酸还原酶NiilcDNA组成。先前对叶子中基因表达的分析表明，该位点触发宿主叶子特异性 Niigenes 的转录后沉默和由 19S 或 35S 启动子驱动的转基因的转录沉默，无论其编码序列及其在基因组中的位置如何。在本文中，我们表明，无论驱动其表达的启动子及其在基因组中的位置如何，携带尼尔序列的转基因都会发生沉默。这种现象发生在根和叶中，尽管 rootNiigenes 与 271 个基因座携带的叶特异性 Niils 序列仅具有 84% 的同一性。相反，携带 beanNiigene（与烟草 Niilgene 有 76% 的同一性）的转基因逃脱了 271 位点的沉默。我们还表明，由玄参花叶病毒 34S 启动子（与 35S 启动子有 63% 的同一性）驱动的转基因也逃脱了 271 位点的沉默。总而言之，这些结果表明转录和转录后沉默的沉默位点和靶（反式）基因的序列之间需要高度的序列相似性。
The transgene locus of the tobacco plant 271 (271 locus) is located on a telomere and consists of multiple copies of a plasmid carrying anNptIImarker gene driven by the cauliflower mosaic virus (CaMV) 19S promoter and the leaf-specific nitrite reductaseNiilcDNA cloned in the antisense orientation under the control of the CaMV 35S promoter. Previous analysis of gene expression in leaves has shown that this locus triggers both post-transcriptional silencing of the host leaf-specificNiigenes and transcriptional silencing of transgenes driven by the 19S or 35S promoter irrespective of their coding sequence and of their location in the genome. In this paper we show that silencing of transgenes carryingNiilsequences occurs irrespective of the promoter driving their expression and of their location within the genome. This phenomenon occurs in roots as well as in leaves although rootNiigenes share only 84% identity with leaf-specificNiilsequences carried by the 271 locus. Conversely, transgenes carrying the beanNiigene (which shares 76% identity with the tobaccoNiilgene) escape silencing by the 271 locus. We also show that transgenes driven by the figwort mosaic virus 34S promoter (which shares 63% identity with the 35S promoter) also escape silencing by the 271 locus. Taken together, these results indicate that a high degree of sequence similarity is required between the sequences of the silencing locus and of the target (trans) genes for both transcriptional and post-transcriptional silencing.