Virus & RNA interference Unit, Department of Virology, Institut Pasteur, CNRS UMR 3569, Université Paris Cité, Paris, France.
Complexity Science Hub (CSH) Vienna, Vienna, Austria.
PLoS Biol. 2022 Jun 29;20(6):e3001715. doi: 10.1371/journal.pbio.3001715. eCollection 2022 Jun.
The origin of RNA interference (RNAi) is usually explained by a defense-based hypothesis, in which RNAi evolved as a defense against transposable elements (TEs) and RNA viruses and was already present in the last eukaryotic common ancestor (LECA). However, since RNA antisense regulation and double-stranded RNAs (dsRNAs) are ancient and widespread phenomena, the origin of defensive RNAi should have occurred in parallel with its regulative functions to avoid imbalances in gene regulation. Thus, we propose a neutral evolutionary hypothesis for the origin of RNAi in which qualitative system drift from a prokaryotic antisense RNA gene regulation mechanism leads to the formation of RNAi through constructive neutral evolution (CNE). We argue that RNAi was already present in the ancestor of LECA before the need for a new defense system arose and that its presence helped to shape eukaryotic genomic architecture and stability.
RNA 干扰 (RNAi) 的起源通常可以用防御假说解释，该假说认为，RNAi 作为一种针对转座元件 (TEs) 和 RNA 病毒的防御机制而进化，并且已经存在于最后的真核生物共同祖先 (LECA) 中。然而，由于 RNA 反义调控和双链 RNA (dsRNA) 是古老而广泛存在的现象，防御性 RNAi 的起源应该与其调节功能平行发生，以避免基因调控的失衡。因此，我们提出了一个关于 RNAi 起源的中性进化假说，其中从原核反义 RNA 基因调控机制定性系统漂移导致通过建设性中性进化 (CNE) 形成 RNAi。我们认为，在需要新的防御系统之前，RNAi 就已经存在于 LECA 的祖先中，它的存在有助于塑造真核生物基因组的结构和稳定性。
