Department of Plant and Microbial Biology, University of California, Berkeley, California, USA.
Int Rev Cell Mol Biol. 2011;292:119-52. doi: 10.1016/B978-0-12-386033-0.00003-7.
Over the past several years, there has been an explosion in our understanding of the mechanisms by which plant transposable elements (TEs) are epigenetically silenced and maintained in an inactive state over long periods of time. This highly efficient process results in vast numbers of inactive TEs; indeed, the majority of many plant genomes are composed of these quiescent elements. This observation has led to the rather static view that TEs represent an essentially inert portion of plant genomes. However, recent work has demonstrated that TE silencing is a highly dynamic process that often involves transcription of TEs at particular times and places during plant development. Plants appear to use transcripts from silenced TEs as an ongoing source of information concerning the mobile portion of the genome. In contrast to our understanding of silencing pathways, we know relatively little about the ways in which TEs evade silencing. However, vast differences in TE content between even closely related plant species suggest that they are often wildly successful at doing so. Here, we discuss TE activity in plants as the result of a constantly shifting balance between host strategies for TE silencing and TE strategies for escape and amplification.
在过去的几年中，我们对植物转座元件（TEs）的机制有了深入的了解，这些机制可以使它们在很长一段时间内被表观遗传沉默并保持非活性状态。这个高效的过程导致了大量的非活性 TEs；事实上，许多植物基因组的大部分都是由这些休眠元件组成的。这一观察结果导致了一种相当静态的观点，即 TEs 代表植物基因组的一个基本惰性部分。然而，最近的研究表明，TE 的沉默是一个高度动态的过程，它通常涉及在植物发育的特定时间和地点转录 TEs。植物似乎利用沉默 TEs 的转录本作为有关基因组移动部分的持续信息来源。与我们对沉默途径的理解相比，我们对 TEs 逃避沉默的方式知之甚少。然而，即使是密切相关的植物物种之间 TE 含量的巨大差异表明，它们通常在这方面非常成功。在这里，我们讨论了植物中转座元件的活性，这是宿主 TE 沉默策略和 TE 逃避和扩增策略之间不断变化的平衡的结果。
