Pyle Jesse D, Keeling Patrick J, Nibert Max L
Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA; Harvard Ph.D. Program in Virology, Division of Medical Sciences, Harvard University, Boston, MA 02115, USA.
Department of Botany, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.
Virus Res. 2017 Apr 2;233:95-104. doi: 10.1016/j.virusres.2017.02.015. Epub 2017 Mar 4.
A previously reported Expressed Sequence Tag (EST) library from spores of microsporidian Antonospora locustae includes a number of clones with sequence similarities to plant amalgaviruses. Reexamining the sequence accessions from that library, we found additional such clones, contributing to a 3247-nt contig that approximates the length of an amalga-like virus genome. Using A. locustae spores stored from that previous study, and new ones obtained from the same source, we newly visualized the putative dsRNA genome of this virus and obtained amplicons yielding a 3387-nt complete genome sequence. Phylogenetic analyses suggested it as prototype strain of a new genus in family Amalgaviridae. The genome contains two partially overlapping long ORFs, with downstream ORF2 in the +1 frame relative to ORF1 and a proposed motif for +1 ribosomal frameshifting in the region of overlap. Subsequent database searches using the predicted fusion protein sequence of this new amalga-like virus identified related sequences in the transcriptome of a basal hexapod, the springtail species Tetrodontophora bielanensis. We speculate that this second new amalga-like virus (contig length, 3475 nt) likely also derived from a microsporidian, or related organism, which was associated with the springtail specimens at the time of sampling for transcriptome analysis. Other findings of interest include evidence that the ORF1 translation products of these two new amalga-like viruses contain a central region of predicted α-helical coiled coil, as recently reported for plant amalgaviruses, and transcriptome-based evidence for another new amalga-like virus in the transcriptome of another basal hexapod, the two-pronged bristletail species Campodea augens.
先前报道的来自蝗虫微孢子虫（Antonospora locustae）孢子的表达序列标签（EST）文库包含一些与植物融合病毒具有序列相似性的克隆。重新检查该文库中的序列登录号时，我们发现了更多此类克隆，形成了一个3247 nt的重叠群，其长度接近类融合病毒基因组的长度。利用先前研究中保存的蝗虫微孢子虫孢子以及从同一来源获得的新孢子，我们新观察到了这种病毒假定的双链RNA基因组，并获得了扩增子，产生了一个3387 nt的完整基因组序列。系统发育分析表明它是融合病毒科一个新属的原型菌株。该基因组包含两个部分重叠的长开放阅读框（ORF），下游的ORF2相对于ORF1处于+1阅读框，并且在重叠区域有一个推测的+1核糖体移码基序。随后，使用这种新的类融合病毒的预测融合蛋白序列进行数据库搜索，在基础六足动物弹尾虫物种比氏四齿跳虫（Tetrodontophora bielanensis）的转录组中鉴定出相关序列。我们推测这种第二种新的类融合病毒（重叠群长度为3475 nt）可能也源自一种微孢子虫或相关生物体，它在为转录组分析采样时与弹尾虫标本相关联。其他有趣的发现包括，证据表明这两种新的类融合病毒的ORF1翻译产物包含一个预测的α螺旋卷曲螺旋中心区域，这与最近报道的植物融合病毒情况相同，以及在另一种基础六足动物双尾虫物种奥氏双尾虫（Campodea augens）的转录组中基于转录组的另一种新的类融合病毒的证据。
