Transcriptional characteristics of acetylcholinesterase genes in domestic silkworms (Bombyx mori) exposed to phoxim

This study investigated the transcriptional characteristics of acetylcholinesterase gene (AChE) in domesticated silkworm ( Bombyx mori ) after pesticide phomix induction. We first determined the LC 50 (Lethal Concentration 50) of phomix in 3-day old, 5th instar B. mori , then fed the B. mori with low dose of phoxim and examined the transcription level of two acetylcholinesterase genes ( Bm-AChE-1 and Bm-AChE-2 ) in brain, fat body, midgut and silk gland at 24, 48, 72 and 96 h later using real-time quantitative PCR. The results showed that LC 50 of phoxim on B. mori was 7.86 μg/mL (24 h). After feeding with 4.00 μg/mL phoxim, transcription levels of Bm-AChE-1 and Bm-AChE-2 in brain, fat body and silk gland showed a trend of first increasing and then decreasing. At 24 h, transcription of Bm-AChE-1 and Bm-AChE-2 increased in the brain by 16.22 and 68.71-fold, respectively, while that of Bm-AChE-1 and Bm-AChE-2 in the fat body and silk glands only increased slightly. Moreover, the increase of Bm-AChE-1 was greater than that of Bm-AChE-2 . By contrast, in the midgut, transcription of Bm-AChE-1 and Bm-AChE-2 showed a trend of first decreasing and then increasing to around their initial levels at 96 h. In addition, the results showed that transcription of Bm-AChE-1 was different from that of Bm-AChE-2 in different tissues of B. mori during the metabolism process of phoxim, suggesting that during metabolic process of pesticides, Bm-AChE-1 plays an important role in the fat body, while Bm-AChE-2 plays an important role in the brain. This study provides a scientific rationale for studying the functional differentiation of the two AChE genes.