Department of Medical Entomology, National Institute of Infectious Diseases, Tokyo, Japan.
Heredity (Edinb). 2013 Sep;111(3):216-26. doi: 10.1038/hdy.2013.40. Epub 2013 May 1.
Insecticide resistance develops as a genetic factor (allele) conferring lower susceptibility to insecticides proliferates within a target insect population under strong positive selection. Intriguingly, a resistance allele pre-existing in a population often bears a series of further adaptive allelic variants through new mutations. This phenomenon occasionally results in replacement of the predominating resistance allele by fitter new derivatives, and consequently, development of greater resistance at the population level. The overexpression of the cytochrome P450 gene CYP9M10 is associated with pyrethroid resistance in the southern house mosquito Culex quinquefasciatus. Previously, we have found two genealogically related overexpressing CYP9M10 haplotypes, which differ in gene copy number (duplicated and non-duplicated). The duplicated haplotype was derived from the non-duplicated overproducer probably recently. In the present study, we investigated allelic series of CYP9M10 involved in three C. quinquefasciatus laboratory colonies recently collected from three different localities. Duplicated and non-duplicated overproducing haplotypes coexisted in African and Asian colonies indicating a global distribution of both haplotype lineages. The duplicated haplotypes both in the Asian and African colonies were associated with higher expression levels and stronger resistance than non-duplicated overproducing haplotypes. There were slight variation in expression level among the non-duplicated overproducing haplotypes. The nucleotide sequences in coding and upstream regions among members of this group also showed a little diversity. Non-duplicated overproducing haplotypes with relatively higher expression were genealogically closer to the duplicated haplotypes than the other non-duplicated overproducing haplotypes, suggesting multiple cis-acting mutations before duplication.
昆虫对杀虫剂的抗性是一种遗传因素(等位基因),在强烈的正向选择下,这种等位基因在目标昆虫种群中会不断扩散,从而导致昆虫对杀虫剂的敏感性降低。有趣的是,种群中预先存在的抗性等位基因往往会通过新的突变产生一系列进一步的适应性等位基因变体。这种现象偶尔会导致更适应的新衍生物取代优势抗性等位基因,从而导致种群水平抗性的增强。细胞色素 P450 基因 CYP9M10 的过度表达与南方家蚊 Culex quinquefasciatus 对拟除虫菊酯的抗性有关。先前,我们发现了两种具有亲缘关系的过度表达 CYP9M10 的单倍型,它们在基因拷贝数(重复和非重复)上有所不同。重复的单倍型可能是由非重复的高产者最近衍生而来的。在本研究中,我们调查了三种最近从三个不同地点收集的实验室蚊子 C. quinquefasciatus 中涉及 CYP9M10 的等位基因系列。在非洲和亚洲的种群中,重复和非重复的过度产生的单倍型共存,表明这两个单倍型谱系在全球范围内都有分布。亚洲和非洲群体中的重复单倍型都与更高的表达水平和更强的抗性相关,而非重复的过度产生的单倍型则没有。非重复的过度产生的单倍型之间的表达水平略有差异。这一组成员的编码和上游区域的核苷酸序列也显示出一点多样性。与其他非重复的过度产生的单倍型相比,具有相对较高表达水平的非重复的过度产生的单倍型在系统发生上更接近重复的单倍型,这表明在重复之前存在多个顺式作用突变。