Evolutionary inferences from DNA variation at the 6-phosphogluconate dehydrogenase locus in natural populations of drosophila: selection and geographic differentiation.
Evolutionary inferences from DNA variation at the 6-phosphogluconate dehydrogenase locus in natural populations of drosophila: selection and geographic differentiation.
复制标题
果蝇自然群体中 6-磷酸葡萄糖酸脱氢酶基因座 DNA 变异的进化推论：选择和地理分化。
DOI：
10.1093/genetics/136.1.155
复制
发表时间：
1994
期刊：
影响因子：
3.3
通讯作者：
Aquadro,CF
中科院分区：
文献类型：
--
作者：
Begun,DJ;Aquadro,CF
果蝇中的几个等位酶编码基因显示的模式表明，在这些位点的多态性是平衡选择的目标。一个重要的问题是，这些基因是否具有相似的潜在DNA序列变异的分布，这将表明类似的进化过程发生在这类基因座。一个这样的基因座，6-磷酸葡萄糖酸脱氢酶（Pgd），以前已被证明在美国和澳大利亚表现出快/慢电变体的倾斜变化，美国和非洲之间异常大的电变体频率差异，以及其他模式选择指示。对142株D.黑腹果蝇X染色体收集自几个地理区域，包括北卡罗来纳州、加州和津巴布韦（非洲）。我们还测定了13 D的代表性样品。在北卡罗来纳州收集的黑腹果蝇Pgd基因和来自姊妹物种模拟果蝇的Pgd的单拷贝。虽然一些群体遗传模型预测了作为平衡选择目标的基因中过量的DNA多态性，但D。来自美国的黑腹果蝇样品具有显著降低的DNA多态性水平和非常高的连锁不平衡水平，提供了Pgd或连锁位点处有利突变体的搭便车效应的证据。因此，虽然选择可能影响了Pgd的DNA变异分布，但这些选择事件的确切性质仍然不清楚。由于Pgd区域似乎具有低的交换率，因此该位点的变异水平降低支持了重组率是自然群体中DNA多态性水平的重要决定因素的观点。此外，虽然Pgd和Adh的等位酶变异模式非常相似，但DNA数据显示这些基因的进化历史截然不同。我们观察到D的变异量和分布存在广泛差异。来自美国和津巴布韦的黑腹Pgd样本，这不能用这两个地理区域中快/慢多态性的差异选择来解释。因此，部分隔离群体间的遗传漂变也是决定D.黑腹菌最后，我们在19 D的样品中测定了Pgd的四切割酶变异。simulans的X染色体，并观察到降低水平的DNA变异和高水平的连锁不平衡。这些模式与一些搭便车模型的预测是一致的。
Several allozyme-coding genes in Drosophila melanogaster show patterns suggesting that polymorphisms at these loci are targets of balancing selection. An important question is whether these genes have similar distributions of underlying DNA sequence variation which would indicate similar evolutionary processes occurring in this class of loci. One such locus, 6-phosphogluconate dehydrogenase (Pgd), has previously been shown to exhibit clinal variation for Fast/Slow electromorph variation in the United States and Australia, unusually large electromorph frequency differences between the United States and Africa, and other patterns indicative of selection. We measured four-cutter DNA restriction site and allozyme variation at Pgd among 142 D. melanogaster X chromosomes collected from several geographic regions including North Carolina, California, and Zimbabwe (Africa). We also sequenced a representative sample of 13 D. melanogaster Pgd genes collected in North Carolina and a single copy of Pgd from the sibling species, Drosophila simulans. While some population genetic models predict excess DNA polymorphism in genes which are targets of balancing selection, the D. melanogaster samples from the United States had significantly reduced levels of DNA polymorphism and extraordinarily high levels of linkage disequilibrium, providing evidence of hitchhiking effects of advantageous mutants at Pgd or at linked sites. Therefore, while selection has probably influenced the distribution of DNA variation at Pgd, the precise nature of these selective events remains obscure. Since the Pgd region appears to have low rates of crossing over, the reduced level of variation at this locus supports the idea that recombination rates are important determinants of levels of DNA polymorphism in natural populations. Furthermore, while patterns of allozyme variation are very similar at Pgd and Adh, the DNA data show that the evolutionary histories of these genes are dramatically different. We observed extensive differences in the amount and distribution of variation in D. melanogaster Pgd samples from the United States and Zimbabwe which cannot be explained by differential selection on the Fast/Slow polymorphism in these two geographic regions. Thus, genetic drift among partially isolated populations has also been an important factor in determining the distribution of variation at Pgd in D. melanogaster. Finally, we assayed four-cutter variation at Pgd in a sample of 19 D. simulans X chromosomes and observed reduced levels of DNA variability and high levels of linkage disequilibrium. These patterns are consistent with predictions of some hitchhiking models.