Abstract: 【Aim】 This study aims to investigate whether DNA methylation and histone acetylation are involved in the regulation of immune responses in the silkworm,Bombyx mori. 【Methods】 We performed the phylogenetic analysis of DNA methyltransferase 1 (DNMT1), histone deacetylase (HDAC) I-1, I-2 and histone acetylase 1 (HAT1) from B. mori and other species. We also profiled their mRNA levels after bacterial ( Pseudomonas aeruginosa or  Staphylococcus aureus) infection in the fat body of day-3 5th instar larvae. We then investigated the effects of DNMT inhibitor, HDAC inhibitor and HAT inhibitor on the survival of day-2 5th instar larvae after bacterial infection. 【Results】 Phylogenetic analysis showed that BmDNMT1 is particular and separated from the homologs of other insect taxa. BmHDACs and BmHAT1 are evolutionarily conserved. BmDNMT1, BmHDACs and BmHAT 1 in the fat body had higher expression levels after bacterial challenge. However, no obvious effects of DNMT, HDAC and HAT inhibitors on the survival of silkworm larvae after bacterial infection were observed. 【Conclusion】 The expression levels of BmDNMT1, BmHDACs and BmHAT1 in the fat body of B. mori larvae are up-regulated after infection of P. aeruginosa or S. aureus, suggesting that DNA methylation and histone acetylation/deacetylation might be involved in the regulation of immune responses in the silkworm.

Key words: Bombyx mori, bacterial infection, immune response, DNA methylation, histone acetylation, gene expression