bmnpv-miR-3 facilitates BmNPV infection by modulating the expression of viral P6.9 and other late genes in Bombyx mori

• Published in: Insect biochemistry and molecular biology Vol. 49; pp. 59 - 69
• Main Authors: Singh, C.P., Singh, J., Nagaraju, J.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-06-2014
• Subjects: Animals; Baculovirus; BmNPV; Bombyx - physiology; Bombyx - virology; Bombyx mori; Gene Expression Regulation, Viral; Host-Pathogen Interactions; MicroRNAs - genetics; MicroRNAs - metabolism; miRNA; Nucleopolyhedrovirus - genetics; Nucleopolyhedrovirus - physiology; P6.9; RNA, Viral - genetics; RNA, Viral - metabolism; Transcription, Genetic; Viral Proteins - genetics; Viral Proteins - metabolism; miRNA; Bombyx mori; P6.9; Baculovirus; BmNPV
• ISSN: 0965-1748; 1879-0240
• DOI: 10.1016/j.ibmb.2014.03.008

During the last decade, microRNAs (miRNAs) have emerged as fine tuners of gene expression in various biological processes including host–pathogen interactions. Apart from the role of host encoded miRNAs in host–virus interactions, recent studies have also indicated the key role of virus-encoded miRNAs in the regulation of host defense responses. In the present study, we show that bmnpv-miR-3, a Bombyx mori nucleopolyhedrovirus (BmNPV) encoded miRNA, regulates the expression of DNA binding protein (P6.9) and other late genes, vital for the late stage of viral infection in the host, Bombyx mori. We have performed both cell culture and in vivo experiments to establish the role of bmnpv-miR-3 in the infection cycle of BmNPV. Our findings showed that bmnpv-miR-3 expresses during early stage of infection, and negatively regulates the expression of P6.9. There was an upregulation in P6.9 expression upon blocking of bmnpv-miR-3 by Locked Nucleic Acid (LNA), whereas overexpression of bmnpv-miR-3 resulted in a decreased expression of P6.9. Besides, a remarkable enhancement and reduction in the viral loads were observed upon blocking and overexpression of bmnpv-miR-3, respectively. Furthermore, we have also assessed the host immune response using one of the Lepidoptera-specific antimicrobial proteins, Gloverin-1 upon blocking and overexpression of bmnpv-miR-3, which correlated viral load with the host immune response. All these results together; clearly imply that bmnpv-miR-3-mediated controlled regulation of BmNPV late genes in the early stage of infection helps BmNPV to escape the early immune response from the host.
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•BmNPV-encoded miRNA, bmnpv-miR-3, negatively regulates the expression of viral P6.9 in the early stage of infection.•bmnpv-miR-3 also regulates the expression of other viral late genes either directly or indirectly.•Inhibition and overexpression of bmnpv-miR-3 positively and negatively affects BmNPV proliferation, respectively.•Viral load induces host immune response and its controlled proliferation can avoid host recognition.•bmnpv-miR-3 helps virus to avoid host immune recognition by lowering down the viral load in the early stage of infection.