Inglis Peter W, Santos Luis Arthur V M, Craveiro Saluana R, Ribeiro Bergmann M, Castro Maria Elita B
Embrapa Recursos Genéticos e Biotecnologia, Parque Estação Biológica, Brasília, DF, Brazil.
Departamento de Biologia Celular, Universidade de Brasília-UnB, Brasília, DF, Brazil.
Arch Virol. 2021 Jan;166(1):125-138. doi: 10.1007/s00705-020-04858-2. Epub 2020 Oct 27.
In a comparative analysis of genome sequences from isolates of the baculovirus Chrysodeixis includens nucleopolyhedrovirus (ChinNPV) from Brazil and Guatemala, we identified a subset of isolates possessing chimeric genomes. We identified six distinct phylogenetically incongruous regions (PIRs) dispersed in the genomes, of between 279 and 3345 bp in length. The individual PIRs possessed high sequence similarity among the affected ChinNPV isolates but varied in coverage in some instances. The donor for four of the PIRs implicated in horizontal gene transfer (HGT) was identified as Trichoplusia ni single nucleopolyhedrovirus (TnSNPV), an alphabaculovirus closely related to ChinNPV, or another unknown but closely related virus. BLAST searches of the other two PIRs returned only ChinNPV sequences, but HGT from an unknown donor baculovirus cannot be excluded. Although Chrysodeixis includens and Trichoplusia ni are frequently co-collected from soybean fields in Brazil, pathogenicity data suggest that natural coinfection of C. includens larvae with ChinNPV and TnSNPV is probably uncommon. Additionally, since the chimeric ChinNPV genomes with tracts of TnSNPV sequence were restricted to a single monophyletic lineage of closely related isolates, a model of progressive restoration of the native DNA sequence by recombination with ChinNPV possessing a fully or partially non-chimeric genome is reasonable. However, multiple independent HGT from TnSNPV to ChinNPV during the evolution of these isolates cannot be excluded. Mortality data suggest that the ChinNPV isolates with chimeric genomes are not significantly different in pathogenicity towards C. includens when compared to most other ChinNPV isolates. Exclusion of the PIRs prior to phylogenetic analysis had a large impact on the topology of part of the maximum-likelihood tree, revealing a homogenous clade of three isolates (IB, IC and ID) from Paraná state in Brazil collected in 2006, together with an isolate from Guatemala collected in 1972 (IA), comprising the lineage uniquely affected by HGT from TnSNPV. The other 10 Brazilian ChinNPV isolates from Paraná, Mato Grosso, and Minas Gerais states showed higher variability, where only three isolates from Paraná state formed a monophyletic group correlating with geographical origin.
在对来自巴西和危地马拉的斜纹夜蛾核型多角体病毒（ChinNPV）分离株的基因组序列进行比较分析时，我们鉴定出了一部分具有嵌合基因组的分离株。我们在基因组中发现了六个不同的系统发育不一致区域（PIRs），长度在279至3345 bp之间。各个PIRs在受影响的ChinNPV分离株中具有高度的序列相似性，但在某些情况下覆盖范围有所不同。四个与水平基因转移（HGT）相关的PIRs的供体被确定为粉纹夜蛾单核衣壳核型多角体病毒（TnSNPV），这是一种与ChinNPV密切相关的甲型杆状病毒，或者是另一种未知但密切相关的病毒。对另外两个PIRs进行BLAST搜索时仅返回了ChinNPV序列，但不能排除来自未知供体杆状病毒的HGT。尽管在巴西的大豆田中经常同时采集到斜纹夜蛾和粉纹夜蛾，但致病性数据表明，ChinNPV和TnSNPV对斜纹夜蛾幼虫的自然共感染可能并不常见。此外，由于具有TnSNPV序列片段的嵌合ChinNPV基因组仅限于一个密切相关分离株的单系谱系，因此通过与具有完全或部分非嵌合基因组的ChinNPV重组来逐步恢复天然DNA序列的模型是合理的。然而，不能排除在这些分离株的进化过程中TnSNPV向ChinNPV发生多次独立HGT的可能性。死亡率数据表明，与大多数其他ChinNPV分离株相比，具有嵌合基因组的ChinNPV分离株对斜纹夜蛾的致病性没有显著差异。在系统发育分析之前排除PIRs对最大似然树部分的拓扑结构有很大影响，揭示了一个由2006年从巴西巴拉那州采集的三个分离株（IB、IC和ID）以及1972年从危地马拉采集的一个分离株（IA）组成的同质分支，该分支是唯一受TnSNPV HGT影响的谱系。来自巴拉那州、马托格罗索州和米纳斯吉拉斯州的其他10个巴西ChinNPV分离株显示出更高的变异性，其中只有来自巴拉那州的三个分离株形成了一个与地理来源相关的单系群。
