棉 花 学 报    Cotton Science   2007，19(3)：233-238

Review on the Molecular Mechanism Underlying AChE Insensitivity to Carbamate and Organophosphate Insecticides in Cotton Aphid ( Aphis gossypii Glover)
DONG Shuang-lin，LI Fei，CHEN Mao-hua，HAN Zhao-jun
(Key Laboratory of Monitoring and Management of Plant Diseases and Insects，Ministry of Agriculture， Nanjing Agriculture University，Nanjing 210095，China)

Abstract：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.
Key words：molecular mechanism；cotton aphid；acetylcholinesterase(AChE)insensitivity；carbamate and organophosphate insecticides [Full Text，2792KB]