棉蚜乙酰胆碱酯酶对杀虫剂不敏感的分子机制

棉蚜是第一个用RT-PCR方法发现具有2个不同乙酰胆碱酯酶(AChE)基因的昆虫,2个基因编码的氨基酸序列的相似性仅48%.进化分析表明,两者相距甚远,分化于昆虫纲出现以前.从棉蚜2个AChE中发现多个抗药性相关突变位点,但功能表达证实AChE-1可能是两类杀虫剂的主要作用靶标,AChE-1的S431F和A302S突变导致对多种有机磷和氨基甲酸酯类杀虫剂的敏感性降低,但对某些杀虫剂品种的敏感性反而升高.并讨论了需进一步研究的问题.

Review on the Molecular Mechanism Underlying AChE Insensitivity to Carbamate and Organophosphate Insecticides in Cotton Aphid (Aphis gossypii Glover)

The molecular mechanism was reviewed in terms of AChE insensitivity to carbamate and organophosphate insecticides in cotton aphid(Aphis gossypii Glover).Cotton aphid is the first insect to be found with two different AChE genes by RT-PCR approach,providing the direct molecular evidence for the hypothesis that some insects may have another AChE gene besides the one orthologous to the AChE gene found in Drosophila melanogaster.The two genes,sharing only 48% similarity at the amino acid level in cotton aphid,were distant by phylogenetic analysis,and were speculated to be diverged long before the differentiation of insects.Some point mutations were found to correlate with the insecticide resistance in both AChE-1 and AChE-2.Further study with the expressed recombined AChE-1 enzymes with S431F and A302S mutations verified that these two mutations conferred the enzyme insensitivity to pirimicarb and most of other insecticides tested,but with exceptions of increased enzyme sensitivity to some insecticides.Also,the biochemical analysis with the in vitro expressed AChE-1 and AChE-2 indicated that AChE-1,rather than AChE-2,seemed to take the main role in the cholinergic synapses and subsequently to be the target for carbamate and organophosphate insecticides.Some related questions that need to be further clarified were discussed.