Shikata M, Shibata H, Sakurai M, Sano Y, Hashimoto Y, Matsumoto T
Department of Applied Biology, Faculty of Textile Science, Kyoto Institute of Technology, Japan.
J Gen Virol. 1998 Jun;79 ( Pt 6):1547-51. doi: 10.1099/0022-1317-79-6-1547.
The Autographa californica nucleopolyhedrovirus (AcMNPV) does not infect the silkworm and molecular studies on silkworm insusceptibility have not been performed. In cultured cells of the silkworm, the expression of viral genes has been reported. The expression of AcMNPV genes and their effect in vivo and in vitro was studied. In this study, the early gene, the ecdysteroid UDP-glucosyltransferase (egt) gene of AcMNPV, which inactivates the insect moulting hormone by sugar conjugation, was examined to determine whether it would alter the growth of the silkworm. Using wild-type (wt) AcMNPV, the egt gene deletion virus (vEGTDEL), and the virus carrying the egt promoter-lacZ cassette in vEGTDEL (vEGTZ), the egt promoter-driven expression in cultured cells and in nonproductive infection of the silkworm was characterized. Infection of cultured cells with vEGTZ at three different doses occurred in a single cell manner. When budded wt AcMNPV was injected into the fourth and fifth instar larvae, an increase in the amount of virus occurred and caused abnormal larval growth, which resulted in the prolongation or skipping of the larval instar, premature pupation, or death during the pupal stage. For infection of the fourth instar larvae, precocious metamorphosis was observed. When the same amount of vEGTDEL was injected, the alteration of growth did not occur. These results suggest that the egt gene was expressed in the primary infected cells of the silkworm, and that the EGT was secreted into the haemocoel, which significantly altered larval growth.
苜蓿银纹夜蛾核型多角体病毒（AcMNPV）不会感染家蚕，且尚未开展关于家蚕不敏感性的分子研究。在家蚕的培养细胞中，已有病毒基因表达的报道。本研究对AcMNPV基因的表达及其在体内和体外的作用进行了研究。在本研究中，检测了AcMNPV的早期基因——蜕皮甾体UDP -葡萄糖基转移酶（egt）基因，该基因通过糖基化作用使昆虫蜕皮激素失活，以确定其是否会改变家蚕的生长。使用野生型（wt）AcMNPV、egt基因缺失病毒（vEGTDEL）以及在vEGTDEL中携带egt启动子 - lacZ盒的病毒（vEGTZ），对egt启动子驱动的在培养细胞中和在家蚕非生产性感染中的表达进行了表征。用三种不同剂量的vEGTZ感染培养细胞是以单细胞方式发生的。当将出芽的wt AcMNPV注射到四龄和五龄幼虫中时，病毒量增加并导致幼虫生长异常，这导致幼虫龄期延长或跳过、过早化蛹或在蛹期死亡。对于四龄幼虫的感染，观察到了早熟变态。当注射相同量的vEGTDEL时，未发生生长改变。这些结果表明，egt基因在家蚕的初始感染细胞中表达，并且EGT分泌到血淋巴中，这显著改变了幼虫的生长。
