Institut de Biologie de l'Ecole Normale Supérieure, Centre National de la Recherche Scientifique UMR8197, Institut National de La Recherche Médicale U1024, Paris, France.
Heredity (Edinb). 2010 Jul;105(1):14-23. doi: 10.1038/hdy.2010.52. Epub 2010 May 12.
DNA methylation is an epigenetic mark that has key roles in the control of genome activity in plants and mammals. It is critical for the stable silencing of repeat elements and is also involved in the epigenetic regulation of some genes. Despite similarities in the controlling functions of DNA methylation, its dynamics and deposition patterns differ in several respects between plants and mammals. One of the most striking differences is that plants tend to propagate pre-existing DNA methylation states across generations, whereas mammals re-establish them genome wide at every generation. Here, we review our current understanding of DNA methylation in the flowering plant Arabidopsis. We discuss in particular the role of RNAi in the incremental methylation and silencing of repeat elements over successive generations. We argue that paramutation, an epigenetic phenomenon first described in maize, is an extreme manifestation of this RNAi-dependent pathway.
DNA 甲基化是一种表观遗传标记，在植物和哺乳动物中对基因组活性的控制起着关键作用。它对于重复元件的稳定沉默至关重要，并且还参与一些基因的表观遗传调控。尽管 DNA 甲基化的控制功能相似，但在植物和哺乳动物之间，其动态和沉积模式在几个方面存在差异。最显著的差异之一是，植物倾向于在代际间传播预先存在的 DNA 甲基化状态，而哺乳动物则在每一代中重新建立它们的全基因组甲基化状态。在这里，我们回顾了我们目前对开花植物拟南芥中 DNA 甲基化的理解。我们特别讨论了 RNAi 在重复元件的逐步甲基化和沉默中的作用。我们认为，前突变是玉米中首次描述的一种表观遗传现象，是这种依赖于 RNAi 的途径的极端表现。
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