Intron splicing suppresses RNA silencing in Arabidopsis
Intron splicing suppresses RNA silencing in Arabidopsis
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DOI：
10.1111/j.1365-313x.2011.04676.x
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发表时间：
2011-10-01
期刊：
影响因子：
7.2
通讯作者：
Carroll, Bernard J.
中科院分区：
文献类型：
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作者：
Christie, Michael;Croft, Larry J.;Carroll, Bernard J.
转基因沉默是转基因作物生产中的一个主要瓶颈。通常，这些转基因不包含内含子，这是转座子的一个共同特征，转座子也是基因沉默的主要目标。鉴于内含子在内源基因中非常常见，但在转基因和转座子中往往缺乏，我们假设内含子可能抑制基因沉默。为了研究这一点，我们在全基因组范围内分析了拟南芥中无内含子和含内含子基因外显子中的小RNA密度。我们发现，小RNA文库对来自无内含子基因的外显子序列具有很强的富集性。无内含子基因外显子中的小RNA密度与转座元件外显子的密度相当。为了在体内测试这些发现，我们使用转基因报告系统来确定内含子是否能够抑制拟南芥中的基因沉默。在转基因中引入内含子可以减少四倍以上的沉默。与非内含子转录本相比，剪接转录本是RNA依赖的RNA聚合酶6介导的基因沉默的有效底物。这种内含子抑制转基因沉默需要有效的内含子剪接，并依赖于ABH1，人类帽子结合蛋白80的拟南芥同源基因。
Silencing of introduced transgenes constitutes a major bottleneck in the production of transgenic crops. Commonly, these transgenes contain no introns, a feature shared with transposons, which are also prime targets for gene silencing. Given that introns are very common in endogenous genes but are often lacking in transgenes and transposons, we hypothesised that introns may suppress gene silencing. To investigate this, we conducted a genome-wide analysis of small RNA densities in exons from intronless versus intron-containing genes in Arabidopsis thaliana. We found that small RNA libraries are strongly enriched for exon sequences derived from intronless genes. Small RNA densities in exons of intronless genes were comparable to exons of transposable elements. To test these findings in vivo we used a transgenic reporter system to determine whether introns are able to suppress gene silencing in Arabidopsis. Introducing an intron into a transgene reduced silencing by more than fourfold. Compared with intronless transcripts, the spliced transcripts were less effective substrates for RNA-dependent RNA polymerase 6-mediated gene silencing. This intron suppression of transgene silencing requires efficient intron splicing and is dependent on ABH1, the Arabidopsis orthologue of human cap-binding protein 80.