Polydnaviruses (PDVs) are mutualistic endogenous viruses inoculated by some lineages of parasitoid wasps into their hosts, where they facilitate successful wasp development. PDVs include the ichnoviruses and bracoviruses that originate from independent viral acquisitions in ichneumonid and braconid wasps respectively. PDV genomes are fully incorporated into the wasp genomes and consist of (1) genes involved in viral particle production, which derive from the viral ancestor and are not encapsidated, and (2) proviral segments harboring virulence genes, which are packaged into the viral particle. To help elucidating the mechanisms that have facilitated viral domestication in ichneumonid wasps, we analyzed the structure of the viral insertions by sequencing the whole genome of two ichnovirus-carrying wasp species, Hyposoter didymator and Campoletis sonorensis. Assemblies with long scaffold sizes allowed us to unravel the organization of the endogenous ichnovirus and revealed considerable dispersion of the viral loci within the wasp genomes. Proviral segments contained species-specific sets of genes and occupied distinct genomic locations in the two ichneumonid wasps. In contrast, viral machinery genes were organized in clusters showing highly conserved gene content and order, with some loci located in collinear wasp genomic regions. This genomic architecture clearly differs from the organization of PDVs in braconid wasps, in which proviral segments are clustered and viral machinery elements are more dispersed. The contrasting structures of the two types of ichnovirus genomic elements are consistent with their different functions: proviral segments are vehicles for virulence proteins expected to adapt according to different host defense systems, whereas the genes involved in virus particle production in the wasp are likely more stable and may reflect ancestral viral architecture. The distinct genomic architectures seen in ichnoviruses versus bracoviruses reveal different evolutionary trajectories that have led to virus domestication in the two wasp lineages.

中文翻译：

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内源性鱼类病毒的基因组结构揭示了导致寄生蜂中病毒驯化的独特进化途径。

Polydnaviruses（PDVs）是互生的内源病毒，由一些寄生性黄蜂谱系接种到它们的宿主中，在这些宿主中，它们促进了黄蜂的成功发育。PDV包括鱼糜病毒和臂章病毒，它们分别来自鱼腥草和黄con蜂的独立病毒获取。PDV基因组已完全整合到wasp基因组中，并由（1）涉及病毒颗粒生产的基因（其源自病毒祖先而不被衣壳化）和（2）带有毒力基因的前病毒片段组成，这些片段被包装到病毒颗粒中。为了帮助阐明促成鱼鳞龙黄蜂病毒驯化的机制，我们通过对两种携带鱼鳞病毒的黄蜂物种的整个基因组进行测序，分析了病毒插入的结构，Hyposoter didymator和Campoletis sonorensis。具有长支架大小的装配体使我们能够解开内源性鱼类病毒的组织，并揭示了黄蜂基因组中病毒基因座的大量分散。前病毒区段包含物种特定的基因组，并在两个鱼龙类黄蜂中占据不同的基因组位置。相比之下，病毒机器基因组织成簇，显示出高度保守的基因含量和顺序，其中一些基因座位于共线的黄蜂基因组区域。这种基因组结构明显不同于在类巴西鳄黄蜂中的PDV的组织，在后者中，前病毒片段聚集在一起，而病毒机制元件则更加分散。两种类型的鱼鳞病毒基因组元件的对比结构与其不同功能一致：前病毒区段是预期能根据不同宿主防御系统适应的毒力蛋白的媒介，而黄蜂中病毒颗粒产生所涉及的基因可能更稳定，并可能反映祖先的病毒结构。在鱼鳞病毒和狂犬病毒中观察到的独特基因组结构揭示了导致两个黄蜂谱系中的病毒驯化的不同进化轨迹。