State Key Laboratory of Virology and Joint-Lab of Invertebrate Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, PR China.
University of Chinese Academy of Sciences, Beijing 100049, PR China.
J Gen Virol. 2018 Apr;99(4):585-595. doi: 10.1099/jgv.0.001031. Epub 2018 Feb 21.
Autographa californica nucleopolyhedrovirus (AcMNPV) orf5 (ac5) is a group I alphabaculovirus-specific gene of unknown function, although the protein (AC5) was previously reported to be associated with the per os infectivity factor (PIF) complex. The purpose of this study was to study the dynamics of AC5 during AcMNPV infection and to verify whether it is indeed a component of the PIF complex. Transcription and expression analyses suggested that ac5 is a late viral gene. An ac5-deleted recombinant AcMNPV was generated by homologous recombination. A one-step growth curve assay indicated that ac5 was not required for budded virus (BV) production in Sf9 cells. Scanning electron microscopy and transmission electron microscopy demonstrated that the deletion of ac5 did not affect occlusion body (OB) morphology, and nor did it affect the insertion of occlusion-derived virus (ODV) into OBs. Partially denaturing SDS-PAGE and a co-immunoprecipitation assay clearly showed that AC5 was not a component of the PIF complex, while the deletion of ac5 did not affect the formation and presence of the PIF complex. Further analyses showed, however, that AC5 was an OB-specific protein, but it was not detected as a component of BVs or ODVs. Bioassay experiments showed that the oral infectivity of ac5-deleted AcMNPV to third instar Spodoptera exigua larvae was not significantly different from that of the ac5-repaired virus. In conclusion, AC5 is an intrinsic protein of OBs, instead of being a component of the PIF complex, and is not essential for either BV or ODV infection. AC5 is awaiting the assignment of another hitherto unknown function.
苜蓿银纹夜蛾核多角体病毒（AcMNPV）orf5（ac5）是一类未知功能的 I 组α杆状病毒特异性基因，尽管该蛋白（AC5）先前被报道与经口感染因子（PIF）复合物有关。本研究的目的是研究 AcMNPV 感染过程中 AC5 的动态变化，并验证其是否确实是 PIF 复合物的组成部分。转录和表达分析表明 ac5 是一种晚期病毒基因。通过同源重组生成了缺失 ac5 的重组 AcMNPV。一步生长曲线测定表明 ac5 对于 Sf9 细胞中芽生病毒（BV）的产生不是必需的。扫描电子显微镜和透射电子显微镜表明，ac5 的缺失不影响包埋体（OB）形态，也不影响嵌合衍生病毒（ODV）插入 OBs。部分变性 SDS-PAGE 和共免疫沉淀分析清楚地表明，AC5 不是 PIF 复合物的组成部分，而 ac5 的缺失并不影响 PIF 复合物的形成和存在。然而，进一步的分析表明，AC5 是 OB 特异性蛋白，但它未被检测为 BV 或 ODV 的组成部分。生物测定实验表明，缺失 ac5 的 AcMNPV 对三龄期斜纹夜蛾幼虫的口服感染性与修复 ac5 的病毒没有显著差异。总之，AC5 是 OB 的内在蛋白，而不是 PIF 复合物的组成部分，对于 BV 或 ODV 感染不是必需的。AC5 正在等待另一个迄今未知功能的分配。
