The silkworm maggot, Exorista sorbillans, is a well-known larval endoparasitoid of the silkworm Bombyx mori that causes considerable damage to the silkworm cocoon crop. To gain insights into the response mechanism of the silkworm at the protein level, we applied a comparative proteomic approach to investigate proteomic differences in the hemolymph of the female silkworm pupae parasitized by E. sorbillans. In total, 50 differentially expressed proteins (DEPs) were successfully identified, of which 36 proteins were upregulated and 14 proteins were downregulated in response to parasitoid infection. These proteins are mainly involved in disease, energy metabolism, signaling pathways, and amino acid metabolism. Eight innate immune proteins were distinctly upregulated to resist maggot parasitism. Apoptosis-related proteins of cathepsin B and 14-3-3 zeta were significantly downregulated in E. sorbillans-parasitized silkworm pupae; their downregulation induces apoptosis. Quantitative PCR was used to further verify gene transcription of five DEPs, and the results are consistent at the transcriptional and proteomic levels. This was the first report on identification of possible proteins from the E. bombycis-parasitized silkworms at the late stage of parasitism, which contributes to furthering our understanding of the response mechanism of silkworms to parasitism and dipteran parasitoid biology.

The silkworm, Bombyx mori , is a complete metamorphosis insect, the model to study insect physiology and biochemistry. Bombyx mori nucleopolyhedrovirus (BmNPV) is a principal pathogen of the silkworm and its host range is restricted to silkworm larvae, requiring interaction with larvae to accomplish virus replication. Prothoracic glands (PGs) are a model for synthetic ecdysone with regulating insect growth and development. This study performed a transcriptome analysis of silkworm PGs after BmNPV infection. Transcriptome data were annotated with KEGG, GO, and shown to be of high quality by RT-qPCR. The spatial expression profiles of BmJing and BmAryl indicate that they may be specifically expressed in silkworm PGs. The RT-qPCR results of the DEGs in the PGs of BmNPV-infected larvae at 24, 48, and 72 h and at the developmental stages of days-6 and 7, comparing to day-3, reveal that the DEGs may be related to the BmNPV infection via promoting early maturation in the latter half of the silkworm fifth instar. This study is the first report on the identification of possible genes in PGs correlating with the precocious molting and metamorphosis of silkworm larvae under BmNPV infection in the latter half of the fifth instar. Our findings will help to address the interactions between BmNPV infection and host developmental response. This work provides a new perspective on BmNPV infection and host developmental response, as well as suggesting candidate genes for further research.