Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
Department of Biological and Environmental Sciences, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi 753-8515, Japan.
Virus Res. 2018 Apr 2;249:124-131. doi: 10.1016/j.virusres.2018.03.011. Epub 2018 Mar 21.
Lepidopteran nucleopolyhedroviruses have distinct viral tissue tropisms in host larvae. We previously identified the Bm8 gene of Bombyx mori nucleopolyhedrovirus (BmNPV), the product of which inhibits viral propagation in the middle silk gland (MSG). However, it is unknown whether this inhibitory function of the Bm8 protein is specific to MSGs. Here we generated a Bm8-disrupted recombinant BmNPV expressing green fluorescent protein (GFP) and examined viral propagation in B. mori cultured cells and larvae. We found that Bm8-disrupted BmNPV produced fewer budded viruses and more occlusion bodies (OBs) than the wild-type virus in both cultured cells and larvae. Microscopic observation of OB production and GFP expression revealed that Bm8 disruption accelerated the progression of viral infection in various larval tissues. Furthermore, quantitative reverse transcription-polymerase chain reaction experiments showed that the loss of Bm8 enhanced viral gene expression in BmNPV-infected larval tissues. These results indicate that the Bm8 protein suppresses viral propagation to varying degrees in each larval tissue, which may establish BmNPV tissue tropisms in B. mori larvae.
鳞翅目核多角体病毒在宿主幼虫中有明显的病毒组织嗜性。我们之前鉴定了家蚕核型多角体病毒（BmNPV）的 Bm8 基因，其产物抑制中肠（MSG）中的病毒增殖。然而，Bm8 蛋白的这种抑制功能是否特异性针对 MSGs 尚不清楚。在这里，我们生成了一种表达绿色荧光蛋白（GFP）的 Bm8 缺失重组 BmNPV，并检查了家蚕培养细胞和幼虫中的病毒增殖。我们发现，与野生型病毒相比，Bm8 缺失的 BmNPV 在培养细胞和幼虫中产生的芽生病毒更少，而产生的包埋体（OB）更多。OB 产生和 GFP 表达的显微镜观察表明，Bm8 缺失加速了病毒在各种幼虫组织中的感染进展。此外，定量逆转录聚合酶链反应实验表明，Bm8 的缺失增强了 BmNPV 感染幼虫组织中的病毒基因表达。这些结果表明，Bm8 蛋白在每个幼虫组织中都不同程度地抑制病毒的增殖，这可能在家蚕幼虫中建立了 BmNPV 的组织嗜性。
