Impact Of Population Structure On Evolution Of Gene Associated With Pyrethroid Resistance In Musca Domestica

Musca domestica is a probable mechanical vector of more than 65 human and animal intestinal diseases, while it has also been used as a model insect to discover the characters of adaptive evolution. It was found that nature selection gave impact on evolution of gene associated with pyrethroid resistance in Musca domestica by analyzing the population genetic structure and the kdr allele.1. A wild survey was conducted in the summer of 2003 and 2004 to evaluate resistance to deltamethrin in house flies from seventeen urban garbage dumps in the cities of Beijing, Tianjin and Zhangjiakou. Relative to a susceptible laboratory strain, wild house flies from all populations exhibited 13- to 250-fold resistance to deltamethrin at the LD₅0. The PBO synergism coefficient was 27- to 124- fold in 11 populations collected from Beijing.2. Competitive PCR amplification of specific allele (cPASA) assay was used to detect the presence of the kdr and super-kdr alleles associated with pyrethroid resistance in wild populations. The kdr frequencies ranged from 0.08 to 0.56, and no difference between fale and female individuals of house flies.3. To verify the PASA procedure, a PCR-allele specific oligo nucleotide probe (PCR-ASO) method was used to check the accuracy of PASA. The accordance percentage was 97%.4. Regression analysis indicated a significant correlation between kdr allele frequencies and the levels of resistance to knockdown by deltamethrin based on LD₅0(r_yx = 0.8917, P - 0.0001 for H₀:r_yx = 0).5. No super-kdr allele was found in the individuals of any house flies of populations.6. With the probes of oligo repeat nucleotide (GT)₈, (CAC)₅, (GATA)₄ marked by DIG, some microsatellite DNA were isolated from the partial genomic DNA library from Musca Domestica. 4 out of 768 reconstructed plasmids were found inserted Microsatellite DNA sequence (Accession number: AY593724, DQ004272, DQ004273, DQ004274). Among them there are two loci with polymorphism by detection and the number of alleles on them is 10 respectively, which can be the molecular markers for genetic analysis.7. Genotypic linkage disequilibrium test showed microsatellite loci was independent. Hardy-Weinberg equilibrium was rejected at the 5% significance level in every population at the mocrosatellite loci and was heterozygote deficiency. But only 6 out of 15 of populations deviated from Hardy-Weinberg equilibrium because of heterozygote excess.8. Bottleneck program established the allele frequency distribution and detected it was approximately L-shaped (as expected under mutation-drift equilibrium) in 2 populations, while it was recent bottlenecks provoke a mode shift in 13 populations.9. With the microsatellite loci, F statistic values showed that Fit was 38.49%, Fst was 7.11%, and Fis was 33.78%; R statistic values showed that Rit was 59.8%, Rst was 15.66, and Rit was 52.34%. The differentiation within populations was higher than that between populations.