Molecular cloning, heterogenous expression and the induction profiles after organophosphate phoxim exposure of the carboxylesterase Bmae33 in the silkworm, Bombyx mori

Abstract

Carboxylesterases (COEs) are a multifunctional supergene family and some of them play important roles in hydrolyzing a wide variety of carboxylic acid esters. In insects, COEs are related to xenobiotic detoxification, pheromone degradation and developmental regulation. In the present study, one silkworm COE Bmae33 gene, an ortholog to other Lepidopteran odorant-degrading esterases, was cloned and exogenously expressed in Escherichia coli. The results indicate that the Bmae33 gene contained a 1, 656 bp open reading frame, encoding a protein of 551 amino acids. The molecular weight of predicted protein was 62.15 kDa, and the isoelectric point was 5.87. RT-PCR analysis showed that Bmae33 was highly expressed in the head, fat body and integument of the silkworm larvae. Recombinant protein of Bmae33 was purified by His-tag affinity column, and its antibody was prepared. Western blotting analysis showed that the recombinant protein was purified successfully. In addition, the larvae and adults of the silkworm were exposed by volatile organophosphorus (OP) insecticide phoxim, respectively. After exposure, the expression of Bmae33 gene could be up-regulated by phoxim in the silkworm larval head and adult antennae. The results presented in this study provided useful information for further understanding of the odorant detoxification roles.

Key words: Bombyx mori, carboxylesterase, recombinant expression, phoxim, induction.