The discovery of cruciviruses revealed the most explicit example of a common protein homologue between DNA and RNA viruses to date. Cruciviruses are a novel group of circular Rep-encoding single-stranded DNA (ssDNA) (CRESS-DNA) viruses that encode capsid proteins that are most closely related to those encoded by RNA viruses in the family Tombusviridae. The apparent chimeric nature of the two core proteins encoded by crucivirus genomes suggests horizontal gene transfer of capsid genes between DNA and RNA viruses. Here, we identified and characterized 451 new crucivirus genomes and 10 capsid-encoding circular genetic elements through de novo assembly and mining of metagenomic data. These genomes are highly diverse, as demonstrated by sequence comparisons and phylogenetic analysis of subsets of the protein sequences they encode. Most of the variation is reflected in the replication-associated protein (Rep) sequences, and much of the sequence diversity appears to be due to recombination. Our results suggest that recombination tends to occur more frequently among groups of cruciviruses with relatively similar capsid proteins and that the exchange of Rep protein domains between cruciviruses is rarer than intergenic recombination. Additionally, we suggest members of the stramenopiles/alveolates/Rhizaria supergroup as possible crucivirus hosts. Altogether, we provide a comprehensive and descriptive characterization of cruciviruses.

中文翻译：

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通过挖掘元基因组数据揭示十字形病毒的多样性。

交叉病毒的发现揭示了迄今为止DNA和RNA病毒之间常见蛋白质同源性的最明确例子。Cruciviruses是一组新的圆形代表编码单链DNA（ssDNA）（CRESS-DNA）病毒，其被最密切相关的那些在家庭中通过RNA病毒编码的编码衣壳蛋白番茄丛矮病毒科。交叉病毒基因组编码的两种核心蛋白具有明显的嵌合性质，表明衣壳基因在DNA和RNA病毒之间水平转移。在这里，我们通过从头鉴定并鉴定了451个新的十字病毒基因组和10个编码衣壳的环状遗传元件宏基因组数据的组装和挖掘。这些基因组具有高度多样性，如序列比较和对它们编码的蛋白质序列子集的系统发育分析所证明。大多数变异反映在复制相关蛋白（Rep）序列中，许多序列多样性似乎是由于重组引起的。我们的结果表明，重组病毒往往在衣壳蛋白相对相似的组间更频繁地发生，并且在交叉病毒之间Rep蛋白结构域的交换比基因间重组更为罕见。此外，我们建议将stramenopiles / alveolates / Rhizaria超群成员作为可能的交叉病毒宿主。总而言之，我们提供了十字形病毒的全面描述性特征。