Differentially expressed genes in the silk gland of silkworm (Bombyx mori) treated with TiO2 NPs

Silk gland is a silkworm organ where silk proteins are synthesized and secreted. Dietary supplement of TiO2 nanoparticles (NPs) promotes silk protein synthesis in silkworms. In this study, digital gene expression (DGE) tag was used to analyze the gene expression profile of the posterior silk gland of silkworms that were fed with TiO2 NPs. In total, 5,702,823 and 6,150,719 clean tags, 55,096 and 74,715 distinct tags were detected in TiO2 NPs treated and control groups, respectively. Compared with the control, TiO2 NPs treated silkworms showed 306 differentially expressed genes, including 137 upregulated genes and 169 downregulated genes. Of these differentially expressed genes, 106 genes were related to silk protein synthesis, among which 97 genes were upregulated and 9 genes were downregulated. Pathway mapping using the Kyoto Encyclopedia of Genes and Genomes (KEGG) showed that 20 pathways were significantly enriched in TiO2 NPs treated silkworms, and the metabolic pathway-related genes were the most significantly enriched. The DGE results were verified by qRT-PCR analysis of eight differentially expressed genes. The DGE and qRT-PCR results were consistent for all three upregulated genes and three of the five downregulated genes, but the expression trends of the remaining two genes were different between qRT-PCR and DGE analysis. This study enhances our understanding of the mechanism of TiO2 NPs promoted silk protein synthesis.