论文部分内容阅读
Extensive use of insecticides on cotton has prompted resistance development in the cotton aphid,Aphis gossypii (Glover) in China.A deltamethrin-selected population of cotton aphids from Xinjiang Uygur Autonomous Region,China with 228.59-fold higher resistance to deltamethrin was used to examine how carboxylesterase conferred resistance to this pyrethroid insecticide.The carboxylesterase activity in the deltamethrin-resistant strain was 3.67-,2.02- and 1.16-fold of the susceptible strain when using α-naphthyl acetate (α-NA),β-naphthyl acetate (β-NA) and α-naphthyl butyrate (α-NB) as substrates,respectively.Carboxylesterase eDNA was cloned and sequenced from both deltamethrinresistant and susceptible strains.The eDNA contained 1581 bp open reading frames (ORFs)coding a 526 amino acid protein.Only one amino acid substitution (Va187-Ala) was observed between deltamethrin-resistant and susceptible strains but it is not genetically linked to resistance by the catalytic triad and signature motif analysis.The real-time polymerase chain reaction analysis indicated that the resistant strain had a 6.61-fold higher level of carboxylesterase mRNA than the susceptible strain.The results revealed that up-regulation of the carboxylesterase gene,not modified gene structure,may be responsible for the development of resistance in cotton aphids to deltamethrin.