Transposable elements (TEs) constitute a major threat to genome stability and are therefore typically silenced by epigenetic mechanisms. In response, some TEs have evolved counteracting systems to suppress epigenetic silencing. In the model plant Arabidopsis thaliana, two such anti-silencing systems have been identified and found to be mediated by the VANC DNA-binding proteins encoded by VANDAL transposons. Here, we show that anti-silencing systems have rapidly diversified since their origin in eudicots by gaining and losing VANC-containing domains, such as DUF1985, DUF287, and Ulp1, as well as target sequence motifs. We further demonstrate that these motifs determine anti-silencing specificity by sequence, density, and helical periodicity. Moreover, such rapid diversification yielded at least 10 distinct VANC-induced anti-silencing systems in Arabidopsis. Strikingly, anti-silencing of non-autonomous VANDALs, which can act as reservoirs of 24-nt small RNAs, is critical to prevent the demise of cognate autonomous TEs and to ensure their propagation. Our findings illustrate how complex co-evolutionary dynamics between TEs and host suppression pathways have shaped the emergence of new epigenetic control mechanisms.

中文翻译：

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抗沉默系统的快速共同进化塑造了真双子叶植物中 Mu 样 DNA 转座子的侵入性。

转座因子 (TE) 对基因组稳定性构成主要威胁，因此通常被表观遗传机制沉默。作为回应，一些 TE 已经进化出抵消系统来抑制表观遗传沉默。在模型植物拟南芥中，已经鉴定出两个这样的抗沉默系统，并且发现它们是由 VANDAL 转座子编码的 VANC DNA 结合蛋白介导的。在这里，我们表明反沉默系统自起源于真双子叶植物以来通过获得和失去包含 VANC 的结构域（例如 DUF1985、DUF287 和 Ulp1）以及目标序列基序而迅速多样化。我们进一步证明这些基序通过序列、密度和螺旋周期性决定抗沉默特异性。而且，这种快速多样化在拟南芥中产生了至少 10 个不同的 VANC 诱导的抗沉默系统。引人注目的是，非自主 VANDAL 的反沉默可以充当 24-nt 小 RNA 的储库，对于防止同源自主 TE 的消亡并确保它们的传播至关重要。我们的研究结果说明了 TE 和宿主抑制途径之间复杂的共同进化动力学如何塑造了新的表观遗传控制机制的出现。