玉米小斑病菌中一种维多利亚病毒的分离及其基因组全序列分析

Isolation and Full-length Sequence Analysis of a Victorivirus from Bipolaris maydis

从玉米小斑病菌(Bipolaris maydis)中检测发现一种dsRNA(double-stranded RNA)病毒,暂命名为Bipolaris maydis victorivirus 2(BmV2)。电子显微镜下观察到病毒粒子为二十面体球状,直径为40 nm左右、无包膜;病毒基因组为单条dsRNA核酸分子,长度为5222 bp,其基因组结构与其他维多利亚病毒相似,包含两个开放阅读框(ORFs)。序列BLASTx分析发现,BmV2的基因组核酸序列与Coniothyrium minitans RNA virus Illinois isolate(CmRV-IL)具有较高的同源性(78.15%),后者CmRV-IL是单分体病毒科(Totiviridae)维多利亚病毒属(Victorivirus)的暂定种,两者的外壳蛋白(CP)和RNA依赖性RNA聚合酶(RdRp)的氨基酸序列之间的同源性分别为88.02%和89.87%,说明BmV2、CmRV-IL是同一种病毒的不同分离物。基于BmV2和选择的单分体病毒的RdRp氨基酸序列的系统发育分析表明,BmV2与单分体病毒科维多利亚病毒属中的病毒形成了一个单系进化支。

A double-stranded RNA(dsRNA)virus,tentatively named Bipolaris maydis victorivirus 2(BmV2),was detected in the fungus Bipolaris maydis,the causal agent of corn southern leaf blight.Icosahedral,non-enveloped BmV2 virus particles with a mean diameter of 40 nm were observed by electron microscopy.The genome of BmV2 consists of a single dsRNA molecule with 5222 bp in length,containing two open reading frames(ORFs)arranged in a similar manner as victoriviruses.BLASTx analysis showed that the nucleotide sequence of BmV2 genome shares the highest identity(78.15%)with an Illinois isolate of Coniothyrium minitans RNA virus(CmRV-IL),a tentative species of the genus Victorivirus under the family Totiviridae.The amino acid(aa)sequence of the coat protein(CP)and RNA dependent RNA polymerase(RdRp)of BmV2share 88.02%and 89.87%identity with their counterparts from CmRV-IL.It shows that BmV2 and CmRV-IL are different isolates of the same virus.Phylogenetic analysis based on the RdRp aa sequences of BmV2 and selected totiviruses showed that BmV2 formed a monophyletic clade with viruses in Victorivirus.