Abstract: 【Aim】 To investigate the relationship between acetylcholinesterase-2 (AChE2) and chlorpyrifos-resistance in Apolygus lucorum. 【Methods】 The AChE2 gene (Al-ace2) was cloned using RACE method. The amino acid polymorphism and the transcription level of Al-ace2 in the chlorpyrifos-resistant (BZ-R) and susceptible (SLF and BZ) strains of A. lucorum were detected. 【Results】 The Al-ace2 gene contains a 1 935 bp open reading frame, which encodes 644 amino acid residues. The deduced amino acid sequence shows the common properties of AChE, such as the catalytic triad amino acids, the characteristic motif ‘FGESAG’ surrounding the active Ser, oxyanion hole and the choline binding sites. T552M amino acid substitution was only found in Al-ace2 in the resistant strain (BZ-R) with the mutation frequency of 5%, but not in the two susceptible strains (SLF and BZ). The amino acid at position 552 is neither conserved nor near to active sites, suggesting that the T552M substitution has much higher possibility to cause polymorphism among individuals than to contribute to chlorpyrifos resistance in A. lucorum. The transcription level of Al-ace1 was approximately three-fold as high as that of Al-ace2 in SLF, BZ and BZ-R strains. The transcription level of Al-ace2 showed no significant difference among the three strains. 【Conclusion】 The results suggest that AChE2 is likely the minor AChE and might not be involved in chlorpyrifos resistance in the BZ-R strain of A. lucorum.

Key words: Apolygus lucorum, acetylcholinesterase-2, gene cloning, transcription level, chlorpyrifos, pesticide resistance