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Published on: December 29, 2015
Characterization of Bombyx mori nucleopolyhedrovirus with a deletion of bm118
Zhang-Nv Yang1, Hai-Jun Xu, Enoch Y Park
1Institute of Insect Science, Zhejiang University, 268 Kaixuan Road, Hangzhou 310029, Zhejiang, China.
Abstract:
Bombyx mori nucleopolyhedrovirus (BmNPV) ORF118 (bm118) is homologous to Autographa californica nucleopolyhedrovirus (AcMNPV) ORF142, one of the core genes existing in all baculovirus genomes sequenced to date, suggesting that Bm118 plays a critical role in viral infection. In this study, the primary role of Bm118 was investigated by using homologous recombination in Escherichia coli to generate a bm118 knockout bacmid containing the BmNPV genome. In addition, the bm118 rescue bacmid was constructed by transposing a bm118 gene cassette into the polh locus of the bm118 knockout bacmid. Transfection assays demonstrated that the bm118 knockout bacmid was incapable of producing budded virion (BV). Nevertheless, this defect could be partially recovered by a rescue bacmid. Electron microscopy analysis revealed that the bm118 knockout produced aberrant capsids characterized by translucent, elongated nucleocapsids present as bundles within the nuclei. This construct also produced polyhedra lacking virions. These results reveal that Bm118 is essential for BV production and nucelocapsid maturation.
Insights
Bombyx mori nucleopolyhedrovirus ORF118 (Bm118) is essential for producing infectious budded virions (BV). Knocking out this gene results in abnormal nucleocapsid formation and prevents virion assembly within polyhedra.
Area of Science:
- Virology
- Molecular Biology
- Insect Pathology
Background:
- Baculoviruses, such as Bombyx mori nucleopolyhedrovirus (BmNPV), are important tools in biotechnology and research.
- Core genes, like BmNPV ORF118 (bm118), are conserved across baculovirus genomes, indicating critical functions.
- Bm118 is homologous to AcMNPV ORF142, a gene with known importance in baculovirus replication.
Purpose of the Study:
- To investigate the essential role of BmNPV ORF118 (bm118) in the viral life cycle.
- To determine the specific functions of Bm118 in budded virion (BV) production and nucleocapsid maturation.
Main Methods:
- Homologous recombination in Escherichia coli was used to generate a bm118 knockout bacmid.
- A bm118 rescue bacmid was constructed by inserting a bm118 gene cassette.
- Transfection assays and electron microscopy were employed to analyze viral replication and virion morphology.
Main Results:
- The bm118 knockout bacmid was unable to produce infectious budded virions (BV).
- Electron microscopy revealed aberrant, elongated nucleocapsids and incomplete polyhedra formation in the absence of Bm118.
- Partial recovery of BV production was observed with the rescue bacmid.
Conclusions:
- Bm118 is an essential gene for Bombyx mori nucleopolyhedrovirus replication.
- Bm118 plays a critical role in nucleocapsid maturation and the production of infectious budded virions.
- The findings highlight Bm118's importance in the baculovirus life cycle.
