Clinal variation for amino acid polymorphisms at the Pgm locus in Drosophila melanogaster.
Clinal variation for amino acid polymorphisms at the Pgm locus in Drosophila melanogaster.
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作者：
B. Verrelli;W. Eanes
在果蝇的糖酵解途径中，菌落变异是常见的酶，通常被认为是对不同气候的适应性反应。虽然磷酸葡萄糖变位酶(PGM)具有几种等位基因的多态性，但它的独特之处在于它没有临床变异的报道。我们最近对PGM的DNA序列研究发现，广泛的隐含氨基酸多态与等位基因分离。在这项研究中，我们描述了美国东部一个纬度斜面上PGM氨基酸多态在核苷酸水平上的地理变异。对PGM基因的15个SNPs的调查发现，等位基因多态和许多隐含的氨基酸多态存在显著的临床差异。独立性测试表明，该基因区域普遍存在的连锁不平衡可以解释许多氨基酸倾斜区。由两个氨基酸多态定义的单个PGM单倍型与纬度的相关性最强，等位基因频率的变化也最陡峭。我们认为，PGM的克隆选择可能部分解释了该基因座广泛的氨基酸多态现象，并与糖酵解途径中选择的多基因座反应一致。
Clinal variation is common for enzymes in the glycolytic pathway for Drosophila melanogaster and is generally accepted as an adaptive response to different climates. Although the enzyme phosphoglucomutase (PGM) possesses several allozyme polymorphisms, it is unique in that it had been reported to show no clinal variation. Our recent DNA sequence investigation of Pgm found extensive cryptic amino acid polymorphism segregating with the allozyme alleles. In this study, we characterize the geographic variation of Pgm amino acid polymorphisms at the nucleotide level along a latitudinal cline in the eastern United States. A survey of 15 SNPs across the Pgm gene finds significant clinal differentiation for the allozyme polymorphisms as well as for many of the cryptic amino acid polymorphisms. A test of independence shows that pervasive linkage disequilibrium across this gene region can explain many of the amino acid clines. A single Pgm haplotype defined by two amino acid polymorphisms shows the strongest correlation with latitude and the steepest change in allele frequency across the cline. We propose that clinal selection at Pgm may in part explain the extensive amino acid polymorphism at this locus and is consistent with a multilocus response to selection in the glycolytic pathway.