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Bombyx mori nucleopolyhedrovirus Bm46 is essential for efficient production of infectious BV and nucleocapsid
Yang Li1, Jianjia Zhang2, Xiangshuo Kong2
1College of Animal Sciences, Zhejiang University, Hangzhou 310058, PR China; Key Laboratory of Silkworm and Bee Resource Utilization and Innovation of Zhejiang Province, Hangzhou, PR China.
Abstract:
Bombyx mori nucleopolyhedrovirus (BmNPV) orf46 (Bm46), the orthologues of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) ac57, is a highly conserved gene in group Ⅰ and group Ⅱ nucleopolyhedroviruses (NPVs). However, its function in viral life cycle is unclear. Our results indicated that Bm46 transcript was detected from infected cells at 12 h post infection, while Bm46 protein was detectable from 24 to 72 h post infection. Upon the deletion of Bm46, fewer infectious BVs were produced by titer assays, but neither viral DNA synthesis nor occlusion bodies (OBs) production was affected. Electron microscopy revealed that Bm46 knockout interrupted nucleocapsid assembly and occlusion-derived virus (ODV) embedding, resulting in aberrant capsid-like tubular structures accumulated in the RZ (ring zone). Interestingly, this abnormally elongated capsid structures were consistent with the immunofluorescence microscopy results showing that VP39 assembled into long filaments and cables in the RZ. Moreover, DNA copies decreased by 30 % in occlusion bodies (OBs) produced by Bm46-knockout virus. qRT-PCR and Western blot analysis showed that the expression of VP39 was affected by Bm46 disruption. Taken together, our findings clearly pointed out that Bm46 played an important role in BV production and the proper formation of nucleocapsid morphogenesis.
Insights
The Bombyx mori nucleopolyhedrovirus (BmNPV) Bm46 gene is crucial for producing infectious viral particles. Deleting Bm46 disrupts nucleocapsid assembly and reduces viral production, impacting viral morphogenesis.
Area of Science:
- Virology
- Molecular Biology
- Insect Pathology
Background:
- Bombyx mori nucleopolyhedrovirus (BmNPV) orf46 (Bm46) is a conserved gene in NPVs.
- Its precise role in the viral life cycle remains largely unknown.
Purpose of the Study:
- To elucidate the function of the Bm46 gene in the Bombyx mori nucleopolyhedrovirus life cycle.
- To investigate the impact of Bm46 disruption on viral replication and morphogenesis.
Main Methods:
- Gene knockout of Bm46 in BmNPV.
- Viral titer assays to quantify infectious viral production.
- Electron microscopy and immunofluorescence microscopy to observe viral structures.
- qRT-PCR and Western blot to analyze gene expression.
Main Results:
- Bm46 transcript and protein expression timing was determined.
- Bm46 deletion reduced infectious budded virus (BV) production but did not affect viral DNA synthesis or occlusion body (OB) formation.
- Electron microscopy revealed Bm46 knockout disrupted nucleocapsid assembly and ODV embedding, leading to aberrant capsid structures.
- VP39 protein assembled into abnormal filaments in Bm46-knockout infected cells.
- DNA content in OBs decreased by 30% in Bm46-knockout virus.
- Expression of VP39 was significantly affected by Bm46 disruption.
Conclusions:
- Bm46 plays a critical role in Bombyx mori nucleopolyhedrovirus (BmNPV) budded virus (BV) production.
- The gene is essential for proper nucleocapsid morphogenesis and assembly.
- Bm46 influences the formation of infectious viral particles and VP39 expression.
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