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：

---

内源性丝状病毒的基因组结构揭示了导致寄生黄蜂病毒驯化的独特进化途径。


多DNA病毒（PDV）是一种互惠的内源性病毒，由某些寄生蜂谱系接种到宿主体内，促进黄蜂的成功发育。 PDV 包括分别源自姬蜂和茧蜂中独立获得的病毒的姬蜂病毒和茧蜂病毒。 PDV 基因组完全融入黄蜂基因组中，由 (1) 参与病毒颗粒产生的基因组成，这些基因源自病毒祖先且不被衣壳包裹，以及 (2) 含有毒力基因的原病毒片段，这些基因被包装到病毒颗粒中。为了帮助阐明促进姬蜂病毒驯化的机制，我们通过对两种携带姬蜂病毒的黄蜂物种（Hyposoter didymator 和 Campoletis sonorensis）的全基因组进行测序，分析了病毒插入的结构。具有长支架尺寸的组装使我们能够解开内源性丝状病毒的组织，并揭示了黄蜂基因组内病毒位点的相当大的分散性。前病毒片段包含物种特异性基因组，并在两种姬蜂中占据不同的基因组位置。相比之下，病毒机器基因被组织成簇，显示出高度保守的基因内容和顺序，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茧蜂中的 PDV 组织，其中前病毒片段聚集在一起，而病毒机械元件则更加分散。 两种类型的丝状病毒基因组元件的对比结构与其不同的功能一致：原病毒片段是毒力蛋白的载体，预计会根据不同的宿主防御系统进行适应，而黄蜂中参与病毒颗粒产生的基因可能更稳定并可能反映祖先的病毒结构。 icnoviruses 与 bracoviruses 中看到的不同基因组结构揭示了不同的进化轨迹，导致这两个黄蜂谱系中的病毒驯化。