家蚕二分浓核病毒的起源及进化

Origin and Evolution of Bombyx mori Bidensovirus

家蚕二分浓核病毒(Bombyx moribidensovirus,BmBDV)是一种二分DNA病毒,主要侵染家蚕中肠组织的柱状细胞,引发家蚕浓核病。该病毒与细小病毒科的浓核病毒在病毒粒子和基因组结构上有很多相似之处,但是又具有编码DNA聚合酶以及分子质量较大的次要结构蛋白的功能。通过对BmBDV基因序列进行同源性分析以及对其功能进行预测,分析该病毒的可能起源。结果显示,BmBDV病毒基因组VD1链的非结构蛋白基因ns1和主要结构蛋白基因vp起源于细小病毒中的单义浓核病毒;VD1可能从真核生物自合成DNA转座子--波林顿转座子(Polintons)中获得了DNA聚合酶基因。VD2链的非结构蛋白基因ns3与杆状病毒中的颗粒体病毒(Granulovirus)和细小病毒的双义浓核病毒(Ambidensovirus)同源;次要结构蛋白基因mcp起源于双链RNA呼肠孤病毒。家蚕二分浓核病毒复杂的进化历程揭示了物种间基因转移对新病毒产生的重要性。

Bombyx mori bidensovirus(BmBDV)is a bidnavirus that mainly infects the columnar cells of silkworm midgut,causing densonucleosis. BmBDV shares great similarity with Densovirus of the Parvoviridae in virion and genome structures,but it also has the function of encoding DNA polymerase and minor structural protein with large molecular weight.In order to identify the origin of this virus,homology analysis was performed by combining the sequence characteristics and gene functions. It was found that the non-structural protein gene ns1 and major structural protein gene vp of VD1 strand in BmBDV originated from monosemantic Densovirus of Parvoviridae,and VD1 might obtain DNA polymerase gene from the eukaryotic self-synthesizing DNA transposons(the Polintons). Furthermore,non-structural protein gene ns3 of VD2 strand is homologous with Granulovirus of Baculovidae and Ambidensovirus of Parvoviridae,and minor capsid protein gene mcp was derived from reovirus. This complex evolutionary process of BmBDV suggests that gene transfer among species plays an important role in the emergence of new virus.