Epigenetic transitions leading to heritable, RNA-mediated de novo silencing in Arabidopsis thaliana
Epigenetic transitions leading to heritable, RNA-mediated de novo silencing in Arabidopsis thaliana
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DOI：
10.1073/pnas.1413053112
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发表时间：
2015-01-20
影响因子：
11.1
通讯作者：
Baulcombe, David C.
中科院分区：
文献类型：
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作者：
Bond, Donna M.;Baulcombe, David C.
在植物中，RNA指导的DNA甲基化（RdDM），一种小RNA将表观遗传修饰剂引导到靶位点的机制，在沉默转座元件（TE）以维持基因组完整性方面起着重要作用。到目前为止，已经确定了两种RdDM途径：RNA聚合酶IV（PolIV）-RdDM和RNA依赖性RNA聚合酶6（RDR 6）-RdDM。PolIV-RdDM涉及维持TE沉默的自我加强反馈机制，但不能解释表观遗传沉默是如何首先启动的。RDR 6-RdDM的功能是重新建立活性TE的表观遗传沉默，但尚不清楚该途径是否可以在初始非TE基因座诱导DNA甲基化。为了研究RdDM的从头建立，我们使用了活性FLOWWENINGEN表观等位基因的病毒诱导的基因沉默（VIGS）。使用遗传突变体，我们表明，不像PolIV-RdDM，但像RDR 6-RdDM，建立VIGS介导的RdDM需要PolV和DRM 2，但不像Dicer-3和其他PolIV途径的成分。VIGS中的DNA甲基化可能是由病毒衍生的小RNA引导的过程启动的，所述小RNA长度为21/22-nt，并由24-nt sRNA加强或维持。我们证明VIGS-RdDM作为基因沉默的工具可以通过使用具有增加的24-nt sRNA产生的突变体植物来增强RdDM的水平。
In plants, RNA-directed DNA methylation (RdDM), a mechanism where epigenetic modifiers are guided to target loci by small RNAs, plays a major role in silencing of transposable elements (TEs) to maintain genome integrity. So far, two RdDM pathways have been identified: RNA Polymerase IV (PolIV)-RdDM and RNA-dependent RNA Polymerase 6 (RDR6)-RdDM. PolIV-RdDM involves a self-reinforcing feedback mechanism that maintains TE silencing, but cannot explain how epigenetic silencing is first initiated. A function of RDR6-RdDM is to reestablish epigenetic silencing of active TEs, but it is unknown if this pathway can induce DNA methylation at naive, non-TE loci. To investigate de novo establishment of RdDM, we have used virus-induced gene silencing (VIGS) of an active FLOWERING WAGENINGEN epiallele. Using genetic mutants we show that unlike PolIV-RdDM, but like RDR6-RdDM, establishment of VIGS-mediated RdDM requires PolV and DRM2 but not Dicer like-3 and other PolIV pathway components. DNA methylation in VIGS is likely initiated by a process guided by virus-derived small (s) RNAs that are 21/22-nt in length and reinforced or maintained by 24-nt sRNAs. We demonstrate that VIGS-RdDM as a tool for gene silencing can be enhanced by use of mutant plants with increased production of 24-nt sRNAs to reinforce the level of RdDM.