Callaghan A, Guillemaud T, Makate N, Raymond M
Division of Zoology, School of Animal and Microbial Sciences, University of Reading, Whiteknights, UK.
Insect Mol Biol. 1998 Aug;7(3):295-300. doi: 10.1111/j.1365-2583.1998.00077.x.
In Culex pipiens mosquitoes, A2 esterase alleles are co-amplified with B2 esterase alleles in response to selection with organophosphate insecticides. In this study the amplified A2 and B2 sequences were compared between twelve strains from four continents by restriction mapping. The restriction maps were almost identical in each strain throughout 22 kb surrounding the genes, suggesting that this represents a constant core sequence. A polymorphism was found in two strains collected from Egypt and Kenya in the mid 1980s. This polymorphism was present in all copies of the amplicon, which suggests that a mechanism of sequence homogenization was operating, i.e. concerted evolution. These two strains were almost certainly descendants from the same population and migration probably occurred along the River Nile. Although the maps were almost identical in each strain, dot blotting demonstrated that amplification levels differed by up to 13-fold between strains. Thus the presence of the A2-B2 haplotype cannot be used to indicate the level of amplification or any particular degree of resistance.
在致倦库蚊中，A2酯酶等位基因与B2酯酶等位基因共同扩增，以响应有机磷杀虫剂的选择。在本研究中，通过限制性酶切图谱比较了来自四大洲的12个品系的A2和B2扩增序列。在围绕这些基因的22kb区域内，每个品系的限制性酶切图谱几乎相同，这表明这代表了一个恒定的核心序列。在20世纪80年代中期从埃及和肯尼亚收集的两个品系中发现了多态性。这种多态性存在于扩增子的所有拷贝中，这表明存在一种序列均一化机制在起作用，即协同进化。这两个品系几乎肯定是同一群体的后代，迁移可能沿着尼罗河发生。尽管每个品系的图谱几乎相同，但斑点杂交表明品系间的扩增水平差异高达13倍。因此，A2 - B2单倍型的存在不能用于指示扩增水平或任何特定程度的抗性。
