Company Amplification of estl2/esto2 and Correlation Between Esterase Gene Copy Number and Resistance to Insecticides in the Field Culex pipiens pallens Strains Collected From Beijing, China

摘要

Seven field strains of Culex pipiens pallens were evaluated in the summer of 2004 for their susceptibility to three insecticides. Larval bioassays were carried out in accordance with WHO mosquito susceptibility tests. Field samples showed resistance to dichlorvos and propoxur. Low levels of resistance to phoxim were detected compared with the laboratory-susceptible strain. Quantitative analysis showed that co-amplification of estl2 and esto2 occurred in the seven field Cx. pipiens pallens. However, the levels of transcription of estl2/esto2 genes in the field strains indicated a 15.9:1 ratio of esto2 cDNA over estl2 cDNA. Such observed differential transcription of the estl2/esto2 genes showed that the promoters regulating their expression are independent and of different strengths. Regression analysis of expression level of estl2/esto2 gene and LC50 value to insecticides showed a significant correlation between expression level of estl2 gene and LC50 value to dichlorvos. However, correlation of estl2 gene and LC50 value to propoxur and phoxim, or esto2 gene and three kinds of insecticides, was not significant.