Institute of Plant Science and Resources (IPSR), Okayama University, Kurashiki 710-0046, Japan.
Asian Satellite Campuses Institute, Nagoya University, Nagoya 464-8601, Japan; Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
Virus Res. 2019 Mar;262:37-47. doi: 10.1016/j.virusres.2017.11.020. Epub 2017 Nov 21.
Insects are the host and vector of diverse viruses including those that infect vertebrates, plants, and fungi. Recent wide-scale transcriptomic analyses have uncovered the existence of a number of novel insect viruses belonging to an alphavirus-like superfamily (virgavirus/negevirus-related lineage). In this study, through an in silico search using publicly available insect transcriptomic data, we found numerous virus-like sequences related to insect virga/nege-like viruses. Phylogenetic analysis showed that these novel viruses and related virus-like sequences fill the major phylogenetic gaps between insect and plant virga/negevirus lineages. Interestingly, one of the phylogenetic clades represents a unique insect-infecting virus group. Its members encode putative coat proteins which contained a conserved domain similar to that usually found in the coat protein of plant viruses in the family Virgaviridae. Furthermore, we discovered endogenous viral elements (EVEs) related to virga/nege-like viruses in the insect genomes, which enhances our understanding on their evolution. Database searches using the sequence of one member from this group revealed the presence of EVEs in a wide range of insect species, suggesting that there has been prevalent infection by this virus group since ancient times. Besides, we present detailed EVE integration profiles of this virus group in some species of the Bombus genus of bee families. A large variation in EVE patterns among Bombus species suggested that while some integration events occurred after the species divergence, others occurred before it. Our analyses support the view that insect and plant virga/nege-related viruses might share common virus origin(s).
昆虫是多种病毒的宿主和载体，包括感染脊椎动物、植物和真菌的病毒。最近大规模的转录组分析揭示了一些属于α病毒超家族（风疹/新城疫病毒相关谱系）的新型昆虫病毒的存在。在这项研究中，通过使用公开的昆虫转录组数据进行计算机搜索，我们发现了许多与昆虫 virga/nege 样病毒相关的病毒样序列。系统发育分析表明，这些新病毒和相关的病毒样序列填补了昆虫和植物 virga/negevirus 谱系之间的主要系统发育空白。有趣的是，其中一个系统发育分支代表了一个独特的感染昆虫的病毒群。其成员编码假定的外壳蛋白，其中包含一个保守结构域，类似于在 Virgaviridae 科植物病毒的外壳蛋白中通常发现的结构域。此外，我们在昆虫基因组中发现了与 virga/nege 样病毒相关的内源性病毒元件（EVEs），这增强了我们对它们进化的理解。使用该组的一个成员的序列进行数据库搜索显示，这种病毒群存在于广泛的昆虫物种中，表明这种病毒群自远古以来就一直普遍存在感染。此外，我们还展示了这种病毒群在一些蜜蜂科的 Bombus 属物种中的详细 EVE 整合图谱。Bombus 物种之间的 EVE 模式存在很大差异，表明一些整合事件发生在物种分化之后，而另一些则发生在之前。我们的分析支持这样的观点，即昆虫和植物的风疹/新城疫相关病毒可能具有共同的病毒起源。
