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 mu g/mL (24 h). After feeding with 4.00 mu g/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. (C) 2011 Elsevier Inc. All rights reserved.