Functional prediction of DNA methyltransferase in silkworm and expression characteristics under BmNPV infection

【Objective】To clarify basic bioinformatics characteristics of Bombyx mori DNA methyltransferase gene(BmDNMT)in silkworm and its expression before and after infected with Bombyx mori nuclearpolyhedrosisvirus(BmNPV)and to reveal mechanism of DNA methylation in antiviral immunity of silkworm,so as to provide theoretical basis for mining antiviral marker genes and drug target proteins of silkworm.【Method】OrthoDB,MultiLoc2,SherLoc2,PSORTII,SMART,SWISS-MODEL and Schrödinger were used to analyze BmDNMT protein amino acid homology,phylogenetic analysis,subcellular localization and functional domain prediction,tertiary structure homology modeling and small molecule ligand docking pocket prediction,and quantitative real-time PCR(qRT-PCR)was used to analyze temporal and spatial expression characteristics of BmDNMT gene in different tissues of silkworm infected with BmNPV at different times.【Result】BmDNMT gene contained BmDNMT1 and BmDNMT2,which were located on chromosome 8 and chromosome11,respectively. Amino acid sequence of BmDNMT was closely related to that in Manduca sexta. A large amount of BmDNMT1 proteins were in the nucleus and a small amount in the cytoplasm. However,BmDNMT2 protein was abundant in cytoplasm and small in nucleus and mitochondria. BmDNMT1 protein had more functional domains than BmDNMT2 protein,both of which contained DNA methylase functional domains and had potential drug-binding pockets. BmNPV infection could affect expression difference of BmDNMT1 and BmDNMT2 genes in different tissues of silkworm. 4 h after BmNPV infection,the expression difference of these 2 genes in the midgut of silkworm was very obvious,suggesting that DNA methylation of silkworm might have occurred in the early stage of virus infection,and the midgut may be the earliest tissue to respond. After BmNPV infection,relative expression and expression trends of BmDNMT1 and BmDNMT2 genes were not consistent.【Conclusion】Differences in the chromosomal location,subcellular location and functional domains of BmDNMT1 and BmDNMT2 genes are found,and relative expression and expression trends of BmDNMT1 and BmDNMT2 genes in different tissues of silkworm after BmNPV infection are also not consistent,suggesting that BmDNMT1 and BmDNMT2 genes play different roles during DNA methylation. The three-dimensional structures of BmDNMT1 and BmDNMT2 proteins have potential drug-binding pockets and may be drug targets that directly affect DNA methylation status.