Okuyama E, Shibata H, Tachida H, Yamazaki T
Department of Biology, Kyushu University, Japan.
Mol Biol Evol. 1996 Apr;13(4):574-83. doi: 10.1093/oxfordjournals.molbev.a025617.
The nucleotide sequences of the 5'-flanking regions of the duplicated Amy genes in eight sibling species belonging to the melanogaster species subgroup are analyzed. In Drosophila melanogaster, a region of about 450 bp immediately upstream of the translation initiation site of the two paralogous genes (the proximal and distal genes) has sequence similarities. However, we could not detect any significant sequence similarity in the region more upstream than -450. This result indicates that the coding regions of the ancestral Amy gene were duplicated together with 450 bp of the 5'-flanking region as one unit. Multiple alignment of these 450-bp sequences in the proximal and distal genes of all eight species revealed a mosaic pattern of highly conserved and divergent regions. The conserved regions included almost all the putative regulatory elements identified in previous analyses of the sequences. A phylogenetic analysis of the aligned sequences shows that these 450-bp sequences are clustered into the proximal and the distal groups. As a whole, the divergence between groups in this region is very large in contrast to that in the coding regions. Based on the divergence between groups, the 450-bp region is divided into two subregions. We found that the ratios of the divergence between groups to that within groups differ in the two subregions. From these observations, we discuss a possibility of positive selection acting on the subregion immediately upstream of the Amy coding region to cause divergence of regulatory elements of the paralogous genes.
对属于黑腹果蝇种亚组的八个姊妹物种中重复的Amy基因5'侧翼区域的核苷酸序列进行了分析。在黑腹果蝇中，两个旁系同源基因（近端基因和远端基因）翻译起始位点上游约450 bp的区域具有序列相似性。然而，我们在比-450更上游的区域未检测到任何显著的序列相似性。这一结果表明，祖先Amy基因的编码区域与5'侧翼区域的450 bp作为一个单元一起被复制。对所有八个物种近端和远端基因中这450 bp序列的多重比对揭示了高度保守和发散区域的镶嵌模式。保守区域几乎包括了先前序列分析中鉴定出的所有假定调控元件。对排列好的序列进行系统发育分析表明，这些450 bp序列聚为近端和远端两组。总体而言，该区域两组之间的差异与编码区域相比非常大。基于两组之间的差异，将450 bp区域分为两个子区域。我们发现，两组之间的差异与组内差异的比率在两个子区域中有所不同。基于这些观察结果，我们讨论了正选择作用于Amy编码区域紧邻上游的子区域以导致旁系同源基因调控元件发生差异的可能性。
