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MicroRNAs (miRNAs) constitute a novel class of gene expression regulators and are found to be involved in regulating a wide range of biological processes such as development, cell cycle, metabolism, apoptosis, immunity, host-pathogen interactions etc. Generally miRNAs negatively regulate the gene expression at the post-transcriptional level by binding to the complementary target mRNA sequences. These tiny molecules are abundantly found in higher eukaryotes and viruses. Most of the DNA viruses of animals and insects encode miRNAs including baculoviruses. Baculoviruses are the insect-specific viruses that cause severe infection and mortality mainly in insect larvae of the order Lepidoptera, Diptera, and Hymenoptera. These enveloped viruses have multiple applications in biotechnology and biological pest control methods. For a better understanding of baculoviruses, it is necessary to elucidate the molecular basis of insect-baculovirus interactions. Recent advancement in the technologies for studying the gene expression has accelerated the discovery of new players in the insect-baculovirus interactions. MiRNAs are the emerging and fate-determining players of host-viral interactions. The long history of host and virus co-evolution suggests that the virus keeps on evolving its arsenals to succeed in infection whereas the host continues investing in antiviral defense mechanisms. In this review, I aim to highlight the recent information and understanding of the baculovirus-encoding miRNAs and their functions in regulating viral as well as host genes. Additionally, insect-derived miRNAs response to baculovirus infection is also discussed. A detailed critical view about the regulatory roles of miRNAs in insect-baculovirus interactions will help us to understand molecular networks amid these interactions and develop a sustainable antiviral strategy., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2014 Elsevier Ltd. All rights reserved.)