DNA methylation in silkworm genome may provide insights into epigenetic regulation of response to Bombyx mori cypovirus infection.

DNA methylation is an important epigenetic modification that regulates a wide range of biological processes including immune response. However, information on the epigenetics-mediated immune mechanisms in insects is limited. Therefore, in this study, we examined transcriptomes and DNA methylomes in the fat body and midgut tissues of silkworm, Bombyx mori with or without B. mori cytoplasmic polyhedrosis virus (BmCPV) infection. The transcriptional profile and the genomic DNA methylation patterns in the midgut and fat body were tissue-specific and dynamically altered after BmCPV challenge. KEGG pathway analysis revealed that differentially methylated genes (DMGs) could be involved in pathways of RNA transport, RNA degradation, nucleotide excision repair, DNA replication, etc. 27 genes were shown to have both differential expression and differential methylation in the midgut and fat body of infected larvae, respectively, indicating that the BmCPV infection-induced expression changes of these genes could be mediated by variations in DNA methylation. BS-PCR validated the hypomethylation of G2/M phase-specific E3 ubiquitin-protein ligase-like gene in the BmCPV infected midgut. These results demonstrated that epigenetic regulation may play roles in host-virus interaction in silkworm and would be potential value for further studies on mechanism of BmCPV epithelial-specific infection and epigenetic regulation in the silkworm.

Inhibition of miR-274-3p increases BmCPV replication by regulating the expression of BmCPV NS5 gene in Bombyx mori.

Bombyx mori cytoplasmic polyhedrosis virus (BmCPV) is one of the major pathogens that pose a big challenge to the sericulture industry. Growing evidences have shown that microRNAs play key roles in the regulations of host-pathogen interactions in insects. MicroRNAs have been found in silkworms, whether and how they affect the silkworm-BmCPV interactions are still unknown. Here we investigate the effect of miR-274-3p on the BmCPV replication in the BmCPV-infected silkworm larvae. In our study, BmCPV Nonstructural protein 5 (NS5) was identified to be the target of miR-274-3p based on bioinformatics analysis and luciferase reporter assay. The abundance of NS5 was significantly increased in the presence of miR-274-3p inhibitor based on the qRT-PCR and Western blotting results. Further, qRT-PCR results revealed that the expression of polyhedrin gene of BmCPV in the larvae after applying miR-274-3p inhibitor was significantly increased comparing with that of larvae with negative control. Our results suggest that inhibition of miR-274-3p could facilitate BmCPV replication by up-regulating BmCPV NS5 gene expression and are insightful for further exploring the interactions between silkworm and BmCPV.