Provirophages in the Bigelowiella genome bear testimony to past encounters with giant viruses
Provirophages in the Bigelowiella genome bear testimony to past encounters with giant viruses
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DOI：
10.1073/pnas.1506469112
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发表时间：
2015-09-22
影响因子：
11.1
通讯作者：
Maumus, Florian
中科院分区：
文献类型：
--
作者：
Blanc, Guillaume;Gallot-Lavallee, Lucie;Maumus, Florian
病毒颗粒是最近发现的双链DNA病毒卫星，其捕食巨型病毒（核质大DNA病毒; NCLDV），其本身是单细胞真核生物的寄生虫。这种偶联寄生可导致病毒介导的真核细胞死亡率的间接控制。然而，这种三方关系的细节在很大程度上仍未得到探讨。我们已经发现了类似的300个预测基因的推定virophage起源的核基因组中的单细胞游泳Bigelowiella。这些基因的物理聚类表明病毒噬菌体基因组整合到B中。natans基因组。病毒噬菌体插入片段彼此之间显示出高水平的相似性和同线性，表明它们密切相关。病毒噬菌体基因不仅在测序的B中转录。natans菌株，但也在其他Bigelowiella分离株，这表明转录活性的病毒噬菌体插入物广泛存在于Bigelowiella种群。证据表明B. natans也是NCLDV成员的宿主，这通过鉴定其基因组中的NCLDV插入片段来提供。这些推定的大DNA病毒可能被B感染。纳坦病毒。我们还确定了四个重复的元素共享结构和遗传相似性的transpotoxins-一类移动的元素首次发现在巨大的病毒-这可能是独立地插入在B。natans基因组。我们认为，内源性前病毒素可能是有益的病毒噬菌体和B。通过（i）增加病毒噬菌体与NCLDV猎物共感染宿主细胞的机会和（ii）保护宿主细胞免受致命的NCLDV感染，
Virophages are recently discovered double-stranded DNA virus satellites that prey on giant viruses (nucleocytoplasmic large DNA viruses; NCLDVs), which are themselves parasites of unicellular eukaryotes. This coupled parasitism can result in the indirect control of eukaryotic cell mortality by virophages. However, the details of such tripartite relationships remain largely unexplored. We have discovered similar to 300 predicted genes of putative virophage origin in the nuclear genome of the unicellular alga Bigelowiella natans. Physical clustering of these genes indicates that virophage genomes are integrated into the B. natans genome. Virophage inserts show high levels of similarity and synteny between each other, indicating that they are closely related. Virophage genes are transcribed not only in the sequenced B. natans strain but also in other Bigelowiella isolates, suggesting that transcriptionally active virophage inserts are widespread in Bigelowiella populations. Evidence that B. natans is also a host to NCLDV members is provided by the identification of NCLDV inserts in its genome. These putative large DNA viruses may be infected by B. natans virophages. We also identify four repeated elements sharing structural and genetic similarities with transpovirons-a class of mobile elements first discovered in giant viruses-that were probably independently inserted in the B. natans genome. We argue that endogenized provirophages may be beneficial to both the virophage and B. natans by (i) increasing the chances for the virophage to coinfect the host cell with an NCLDV prey and (ii) defending the host cell against fatal NCLDV infections.