Ito Katsuhiko, Fujii Takeshi, Yokoyama Takeshi, Kadono-Okuda Keiko
Department of Science of Biological Production, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo, 183-8509, Japan.
Division of Biotechnology, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, 1-2 Owashi, Tsukuba, Ibaraki, 305-8634, Japan.
Arch Virol. 2018 Dec;163(12):3327-3338. doi: 10.1007/s00705-018-4017-1. Epub 2018 Sep 15.
Bombyx mori bidensovirus (BmBDV) is a pathogen that replicates only in the midgut columnar cells of silkworms, causing fatal disease. Resistance to BmBDV, which does not depend on the viral dose, is determined by a single gene, nsd-2 (resistance gene). Previously, we identified nsd-2 by positional cloning using B. mori genome information and found that this gene encodes a putative amino acid transporter that may function as a receptor for BmBDV. In this study, to understand the relationship between BmBDV and the putative virus receptor, we performed expression analysis of + (allele of nsd-2; susceptibility gene) after virus infection. Quantitative RT-PCR analysis using total RNA isolated from the midgut of an uninfected and a virus-infected silkworm revealed no change in the expression levels of + in the uninfected silkworm, whereas the expression levels of + drastically decreased in the virus-infected silkworm. Moreover, comparison of the expression pattern between the BmBDV-derived transcript and + revealed that the expression level of + decreased with an increase in the virus-derived transcript. In addition, expression analysis of 26 genes encoding other transporters in the midgut demonstrated that the expression levels of three other genes also decreased similarly to the decrease of the expression levels of + after virus infection. Thus, our results suggest that some transporters, including +, are affected by BmBDV infection.
家蚕双顺反子病毒（BmBDV）是一种仅在家蚕中肠柱状细胞中复制并引发致命疾病的病原体。对BmBDV的抗性由单个基因nsd-2（抗性基因）决定，该抗性不依赖于病毒剂量。此前，我们利用家蚕基因组信息通过定位克隆鉴定出了nsd-2，并发现该基因编码一种推定的氨基酸转运蛋白，可能作为BmBDV的受体发挥作用。在本研究中，为了了解BmBDV与推定的病毒受体之间的关系，我们对病毒感染后的 +（nsd-2的等位基因；敏感基因）进行了表达分析。使用从未感染和病毒感染家蚕中肠分离的总RNA进行的定量RT-PCR分析表明，未感染家蚕中 + 的表达水平没有变化，而在病毒感染的家蚕中 + 的表达水平急剧下降。此外，比较BmBDV衍生转录本和 + 的表达模式发现， + 的表达水平随着病毒衍生转录本的增加而降低。另外，对中肠中编码其他转运蛋白的26个基因的表达分析表明，病毒感染后，其他三个基因的表达水平也与 + 的表达水平下降类似地降低。因此，我们的结果表明，包括 + 在内的一些转运蛋白受到BmBDV感染的影响。
