While the biogenesis of microRNAs (miRNAs) in both animals and plants depends on the RNase III Dicer, its partner proteins are considered distinct for each kingdom. Nevertheless, recent discovery of homologs of Hyponastic Leaves1 (HYL1), a “plant-specific” Dicer partner, in the metazoan phylum Cnidaria, challenges the view that miRNAs evolved convergently in animals and plants. Here we show that the HYL1 homolog Hyl1-like a (Hyl1La) is crucial for development and miRNA biogenesis in the cnidarian model Nematostella vectensis. Inhibition of Hyl1La by morpholinos resulted in metamorphosis arrest in Nematostella embryos and a significant reduction in levels of most miRNAs. Further, meta-analysis of morphants of miRNA biogenesis components, like Dicer1, shows clustering of their miRNA profiles with Hyl1La morphants. Strikingly, immunoprecipitation of Hyl1La followed by quantitative PCR revealed that in contrast to the plant HYL1, Hyl1La interacts only with precursor miRNAs and not with primary miRNAs. This was complemented by an in vitro binding assay of Hyl1La to synthetic precursor miRNA. Altogether, these results suggest that the last common ancestor of animals and plants carried a HYL1 homolog that took essential part in miRNA biogenesis and indicate early emergence of the miRNA system before plants and animals separated.

中文翻译：

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刺胞 Nematostella vectensis 中“植物样”HYL1 同源物的功能表征表明其在 microRNA 生物发生中的保守参与

虽然动物和植物中 microRNA (miRNA) 的生物发生依赖于 RNase III Dicer，但它的伙伴蛋白被认为对于每个王国都是不同的。然而，最近在后生动物刺胞动物门中发现的“植物特异性”切块机伙伴 Hyponastic Leaves1 (HYL1) 的同源物对 miRNA 在动植物中趋同进化的观点提出了挑战。在这里，我们表明 HYL1 同源物 Hyl1 样 a (Hyl1La) 对于刺胞动物模型Nematostella vectensis的发育和 miRNA 生物发生至关重要。吗啉对 Hyl1La 的抑制导致线虫的变态停滞胚胎和大多数 miRNA 水平显着降低。此外，对 miRNA 生物发生成分（如 Dicer1）的 morphant 的荟萃分析显示其 miRNA 谱与 Hyl1La morphant 聚类。引人注目的是，Hyl1La 的免疫沉淀和定量 PCR 显示，与植物 HYL1 相比，Hyl1La 仅与前体 miRNA 相互作用，而不与初级 miRNA 相互作用。这通过 Hyl1La 与合成前体 miRNA 的体外结合测定得到补充。总之，这些结果表明动植物的最后一个共同祖先携带了一个 HYL1 同源物，该同源物在 miRNA 生物发生中发挥了重要作用，并表明 miRNA 系统在植物和动物分离之前早期出现。