Comparative Transcriptome Analysis Reveals the Effects of a High-Protein Diet on Silkworm Midgut

The silkworm is a species within the order Lepidoptera and an economic insect. The nutrients are obtained from the leaf and utilized by the silkworm larvae for body growth, development, and cocoon formation. Protein plays a significant functional role in the diet of silkworms. To investigate the impact of the high-protein diet (HPD 6%) on silkworm growth and development, transcriptomic analysis was conducted on the silkworm midgut, and 1724 differentially expressed genes (DEGs) were identified, comprising 803 up-regulated genes and 921 down-regulated genes. The up-regulated genes exhibited the majority pathway of mitochondrial oxidative phosphorylation, ribosome, and ribosome biogenesis in eukaryotes. The down-regulated genes of DEGs were mostly annotated in ABC transporters, lysosome, endocytosis, and sphingolipid metabolism pathways. The comprehensive analysis of DEGs indicated that substantial modifications were observed in various pathways associated with crucial biological processes. HPD 6% decreased oxidative stress and increased mitochondrial activity, ribosomal activity, and DNA repair capacity. Additionally, the ATP levels were increased in the midgut, malpighian tubule, middle silk gland, and posterior silk gland of the HPD 6% group. Moreover, the activities of SOD and NADH were enhanced in the midgut of the HPD 6% group. Our findings provide valuable insights into the wide-ranging effects of an HPD treatment in insects such as silkworms.