Cirera S, Aguadé M
Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Spain.
Mol Biol Evol. 1998 Aug;15(8):988-96. doi: 10.1093/oxfordjournals.molbev.a026014.
In Drosophila melanogaster, the Acp70A gene, which is involved in the postmating reactions of the female, is a single-copy gene. However, in Drosophila subobscura, the gene is duplicated and both copies are transcribed. To study the molecular evolution of the duplication, a 2.1-kb fragment encompassing both copies of the duplication was sequenced for 10 lines of D. subobscura and one line of Drosophila madeirensis. Estimates of the divergence between the two copies of the duplicated region and between the two species studied, D. subobscura and D. madeirensis, revealed that both copies of the Acp70a gene had evolved independently since their duplication. The ratio of nonsynonymous to silent divergence between copies was generally higher than one. The McDonald and Kreitman test revealed an excess of nonsynonymous changes fixed since the duplication and before the split of the D. subobscura and D. madeirensis lineages. These results point to natural selection driving protein evolution after the duplication. Specifically, adaptive evolution appears to have caused the initial differentiation between copies of the N-terminal parts of the proteins, while purifying selection could be responsible for the high conservation of the C-terminal parts.
在黑腹果蝇中，参与雌性交配后反应的Acp70A基因是单拷贝基因。然而，在暗果蝇中，该基因发生了复制，两个拷贝均被转录。为了研究这种复制的分子进化，对10个暗果蝇品系和1个马德拉果蝇品系中包含该复制两个拷贝的2.1 kb片段进行了测序。对复制区域的两个拷贝之间以及所研究的两个物种（暗果蝇和马德拉果蝇）之间的分歧估计表明，Acp70a基因的两个拷贝自复制以来已经独立进化。拷贝之间非同义与同义分歧的比率通常高于1。麦克唐纳和克雷特曼检验显示，自复制以来以及暗果蝇和马德拉果蝇谱系分化之前，固定的非同义变化过多。这些结果表明自然选择在复制后推动了蛋白质进化。具体而言，适应性进化似乎导致了蛋白质N端部分拷贝之间的初始分化，而纯化选择可能是C端部分高度保守的原因。
