Data from: Functional diversification of Argonautes in nematodes: an expanding universe

In the last decade, many diverse RNAi (RNA interference) pathways have been discovered that mediate gene silencing at epigenetic, transcriptional and post-transcriptional levels. The diversity of RNAi pathways is inherently linked to the evolution of Ago (Argonaute) proteins, the central protein component of RISCs (RNAinduced silencing complexes). An increasing number of diverse Agos are have been identified in different species. The functions of most of these proteins are not yet known, but they are generally assumed to play roles in development, genome stability and/or protection against pathogens. Recent research in the nematode Caenorhabditis elegans has expanded the breadth of RNAi functions to include transgenerational epigenetic memory and, possibly, environmental sensing. These functions are inherently linked to the production of secondary siRNAs (small interfering RNAs) that bind to members of a clade of WAGOs (wormspecific Agos). In the present article, we review briefly what is known about the evolution and function of Ago proteins in eukaryotes, including the expansion of WAGOs in nematodes. We postulate that the rapid evolution of WAGOs enables the exceptional functional plasticity of nematodes, including their capacity for parasitism.

近十年来，学界已发现多种不同的RNA干扰（RNA interference, RNAi）通路，这类通路可在表观遗传、转录及转录后水平介导基因沉默。RNAi通路的多样性与Argonaute（Ago）蛋白的演化存在固有联系——该类蛋白是RNA诱导沉默复合物（RNA-induced silencing complexes, RISCs）的核心组分。目前已在不同物种中鉴定出越来越多的Ago蛋白亚型，但其中绝大多数的功能仍未明确，不过普遍认为它们参与发育过程、维持基因组稳定性，或在抵御病原体侵染中发挥作用。以秀丽隐杆线虫（Caenorhabditis elegans）为模型的最新研究，将RNAi的功能范畴拓展至跨代表观遗传记忆，甚至可能涵盖环境感知，而这些功能与结合蠕虫特异性Argonaute（wormspecific Agos, WAGOs）分支成员的次级小干扰RNA（small interfering RNAs, siRNAs）的生成密切相关。本文简要综述了真核生物中Ago蛋白的演化与功能研究现状，包括线虫中WAGOs的扩增现象。我们推测，WAGOs的快速演化赋予了线虫非凡的功能可塑性，包括其寄生能力。