Takahashi A, Tsaur S C, Coyne J A, Wu C I
Department of Ecology and Evolution, University of Chicago, Chicago, IL 60637, USA.
Proc Natl Acad Sci U S A. 2001 Mar 27;98(7):3920-5. doi: 10.1073/pnas.061465098. Epub 2001 Mar 20.
The cuticular hydrocarbon (CH) pheromones in Drosophila melanogaster exhibit strong geographic variation. African and Caribbean populations have a high ratio of 5,9 heptacosadiene/7,11 heptacosadiene (the "High" CH type), whereas populations from all other areas have a low ratio ("Low" CH type). Based on previous genetic mapping, DNA markers were developed that localized the genetic basis of this CH polymorphism to within a 13-kb region. We then carried out a hierarchical search for diagnostic nucleotide sites starting with four lines, and increasing to 24 and 43 lines from a worldwide collection. Within the 13-kb region, only one variable site shows a complete concordance with the CH phenotype. This is a 16-bp deletion in the 5' region of a desaturase gene (desat2) that was recently suggested to be responsible for the CH polymorphism on the basis of its expression [Dallerac, R., Labeur, C., Jallon, J.-M., Knipple, D. C., Roelofs, W. L. & Wicker-Thomas, C. (2000) Proc. Natl. Acad. Sci. 97, 9449--9454]. The cosmopolitan Low type is derived from the ancestral High type, and DNA sequence variations suggest that the former spread worldwide with the aid of positive selection. Whether this CH variation could be a component of the sexual isolation between Zimbabwe and other cosmopolitan populations remains an interesting and unresolved question.
黑腹果蝇的表皮碳氢化合物（CH）信息素表现出强烈的地理变异。非洲和加勒比地区的种群具有较高比例的5,9 - 二十七碳二烯/7,11 - 二十七碳二烯（“高”CH类型），而其他所有地区的种群比例较低（“低”CH类型）。基于先前的遗传图谱，开发了DNA标记，将这种CH多态性的遗传基础定位在一个13 kb的区域内。然后，我们从四条品系开始进行分层搜索，寻找诊断性核苷酸位点，并从全球收集的样本中增加到24条和43条品系。在13 kb区域内，只有一个可变位点与CH表型完全一致。这是一个去饱和酶基因（desat2）5'区域的16 bp缺失，最近基于其表达情况表明该基因与CH多态性有关[Dallerac, R., Labeur, C., Jallon, J.-M., Knipple, D. C., Roelofs, W. L. & Wicker-Thomas, C. (2000) Proc. Natl. Acad. Sci. 97, 9449--9454]。世界性的低类型源自祖先的高类型，DNA序列变异表明前者在正选择的帮助下传播到全球。这种CH变异是否可能是津巴布韦与其他世界性种群之间性隔离的一个组成部分，仍然是一个有趣且未解决的问题。
