Shen Hongxing, Chen Keping, Yao Qin, Yu Wei, Pan Ye, Huo Juan, Xia Hengchuan, Huang Guoping
Institute of Life Sciences, Jiangsu University, 301# Xuefu Road, 212013, Zhenjiang, People's Republic of China.
Virus Genes. 2009 Jun;38(3):487-94. doi: 10.1007/s11262-009-0350-5. Epub 2009 Apr 2.
orf74 of Bombyx mori nucleopolyhedrovirus (BmNPV) is a homologue of uncharacterized orf91 of Autographa californica multicapsid NPV, predicted to encode a protein of 17.3 kDa. RT-PCR showed that the transcription of orf74 was initiated at 12 h post-infection stage. Expression assay indicated that ORF74 localized in the nucleus of infected BmN cells. To study the function of ORF74, an orf74-knockout virus was constructed using bacmid technology. Analysis of the production of budded virions and occlusion bodies, the formation of nucleocapsids, and the level of viral DNA revealed no significant difference among the mutant, the control, and the orf74-repaired virus. Interestingly, bioassay showed that the median lethal time of the orf74-knockout virus was 14.7 h longer than the control virus, but the virus yield was similar to that of control virus. Thus, our data indicated that ORF74 is most likely implicated in the virulence of BmNPV, and is not essential for virus replication.
家蚕核型多角体病毒（BmNPV）的orf74是苜蓿银纹夜蛾多粒包埋核型多角体病毒（AcMNPV）未鉴定的orf91的同源物，预计编码一种17.3 kDa的蛋白质。逆转录聚合酶链反应（RT-PCR）表明，orf74的转录在感染后12小时开始。表达分析表明，ORF74定位于受感染的BmN细胞的细胞核中。为了研究ORF74的功能，使用杆粒技术构建了一种orf74敲除病毒。对出芽病毒粒子和包涵体的产生、核衣壳的形成以及病毒DNA水平的分析表明，突变体、对照和orf74修复病毒之间没有显著差异。有趣的是，生物测定表明，orf74敲除病毒的半数致死时间比对照病毒长14.7小时，但病毒产量与对照病毒相似。因此，我们的数据表明，ORF74最有可能与BmNPV的毒力有关，对病毒复制不是必需的。
