Comeron J M, Aguadé M
Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Spain.
Genetics. 1996 Nov;144(3):1053-62. doi: 10.1093/genetics/144.3.1053.
The Xdh (rosy) region of Drosophila subobscura has been sequenced and compared to the homologous region of D. pseudoobscura and D. melanogaster. Estimates of the numbers of synonymous substitutions per site (Ks) confirm that Xdh has a high synonymous substitution rate. The distributions of both nonsynonymous and synonymous substitutions along the coding region were found to be heterogeneous. Also, no relationship has been detected between Ks estimates and codon usage bias along the gene, in contrast with the generally observed relationship among genes. This heterogeneous distribution of synonymous substitutions along the Xdh gene, which is expression-level independent, could be explained by a differential selection pressure on synonymous sites along the coding region acting on mRNA secondary structure. The synonymous rate in the Xdh coding region is lower in the D. subobscura than in the D. pseudoobscura lineage, whereas the reverse is true for the Adh gene.
已对暗果蝇的Xdh（玫瑰色）区域进行了测序，并与拟暗果蝇和黑腹果蝇的同源区域进行了比较。每个位点的同义替换数（Ks）估计值证实Xdh具有较高的同义替换率。发现非同义替换和同义替换沿编码区的分布是不均匀的。此外，与基因间普遍观察到的关系相反，未检测到Ks估计值与基因沿密码子使用偏好之间的关系。Xdh基因同义替换的这种不均匀分布与表达水平无关，这可以通过编码区同义位点上作用于mRNA二级结构的差异选择压力来解释。暗果蝇Xdh编码区的同义替换率低于拟暗果蝇谱系，而乙醇脱氢酶（Adh）基因则相反。
