School of Biology & Basic Medical Science, Soochow University, Suzhou, 215123, China; National Engineering Laboratory for Modern Silk, Soochow University, Suzhou, China.
School of Biology & Basic Medical Science, Soochow University, Suzhou, 215123, China; Agricultural Biotechnology Research Institute, Agricultural Biotechnology and Ecological Research Institute, Soochow University, Suzhou, 215123, China.
Dev Comp Immunol. 2019 Jul;96:51-57. doi: 10.1016/j.dci.2019.02.017. Epub 2019 Feb 26.
Bombyx mori cypovirus (BmCPV) is one of the most infectious pathogen in sericulture and a member of the family Reoviridae. It specifically infects the midgut of silkworm. The BmCPV genome consists of 10 dsRNAs segments (S1-S10), which have generally been assumed to be monocistronic. In this study, a small open reading frame encoding the peptide S5-sORF, containing 27 amino acid residues, was predicted in a region of the negative (-) strand of BmCPV segment S5. An immunofluorescence assay detected S5-sORF in the cytoplasm and nuclei of BmCPV-infected cells, and it was also detected in the virion with western blotting, suggesting that S5-sORF may be assembled into the BmCPV virion. Viral gene expression was inhibited by overexpressed S5-sORF, and viral multiplication was dose-dependently suppressed by the S5-sORF peptide. A viable recombinant virus, BmCPV-S5-sORF, in which the start codon (ATG) of S5-sORF was mutated to a stop codon (TGA), was generated with reverse genetics. The proliferation of BmCPV was increased by the abolition of S5-sORF expression. Furthermore, the RNA transcript of S5-sORF and small peptide of S5-sORF were involved in BmCPV replication. The expression of genes related to the innate immune pathways and apoptosis in the silkworm were not significantly affected by S5-sORF overexpression. Our results suggest that a viral nucleotide sequence is utilized by the host to generate an antiviral peptide, which may be a novel strategy protecting the host from viral infection.
家蚕质型多角体病毒（BmCPV）是养蚕业中最具传染性的病原体之一，属于呼肠孤病毒科。它专门感染家蚕的中肠。BmCPV 基因组由 10 个 dsRNA 片段（S1-S10）组成，通常被认为是单顺反子。在本研究中，在 BmCPV 片段 S5 的负（-）链的一个区域中预测到一个编码肽 S5-sORF 的小开放阅读框，该肽包含 27 个氨基酸残基。免疫荧光测定法在 BmCPV 感染细胞的细胞质和细胞核中检测到 S5-sORF，并用 Western blot 在病毒粒子中也检测到 S5-sORF，表明 S5-sORF 可能组装到 BmCPV 病毒粒子中。病毒基因表达被过表达的 S5-sORF 抑制，并且 S5-sORF 肽剂量依赖性地抑制病毒增殖。通过反向遗传学产生了一种具有活性的重组病毒 BmCPV-S5-sORF，其中 S5-sORF 的起始密码子（ATG）突变为终止密码子（TGA）。S5-sORF 表达的消除增加了 BmCPV 的增殖。此外，S5-sORF 的 RNA 转录物和 S5-sORF 的小肽参与了 BmCPV 的复制。S5-sORF 过表达对家蚕先天免疫途径和细胞凋亡相关基因的表达没有显著影响。我们的结果表明，宿主利用病毒核苷酸序列产生抗病毒肽，这可能是宿主抵御病毒感染的一种新策略。
