Characteristics of phoxim-exposed gene transcription in the silk gland of silkworms

• We presented an overview of gene expression at transcription level in the silk gland of Bombyx mori exposed to phoxim.
• 270 Genes exhibited at least 2.0-fold changes, with 249 being up-regulated and 21 being down-regulated.
• Gene ontology annotation and pathway analysis were performed to reveal the potential involvements in different processes.
• We detected that phoxim-exposure induce the apoptosis of silk gland.
• We discovered that the level of fibroin gene transcription is reduced after phoxim-exposure.

Silkworm (Bombyx mori), a model Lepidoptera insect, is an important economic insect. Its silk gland is the important organ for silk protein synthesis and secretion. Phoxim exposure causes deficient cocooning of silkworm and has become one of the major negative factors for the silk industry. To study the impact of phoxim exposure on silk gland, using gene chip technology, we examined differentially expressed genes in silk gland after silkworms were exposed to phoxim (4.0 μg/mL) for 24 h. Functional annotation, classification and KEGG signaling pathway analysis were performed. The results showed that out of 3206 genes detected in silk gland after phoxim exposure, 270 were differentially expressed significantly, including 249 up-regulated genes and 21 down-regulated genes. These differentially expressed genes related to apoptosis, detoxification and protein degradation were selected. Using qRT-PCR, the expression levels of 9 genes involved in apoptosis, detoxification and protein degradation were validated. In addition, the expression profiles of three related fibroin synthesis genes (Fib-H, Fib-L and P25) were analyzed. Our results showed that phoxim exposure induced apoptosis of silk gland cells and inhibition of fibroin synthesis. This may be the cause of deficient silkworm cocooning.

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