Meyerowitz E M, Martin C H
J Mol Evol. 1984;20(3-4):251-64. doi: 10.1007/BF02104731.
The 68C puff is a highly transcribed region of the Drosophila melanogaster salivary gland polytene chromosomes. Three different classes of messenger RNA originate in a 5000-bp region in the puff; each class is translated to one of the salivary gland glue proteins sgs-3, sgs-7, or sgs-8. These messenger RNA classes are coordinately controlled, with each RNA appearing in the third larval instar and disappearing at the time of puparium formation. Their disappearance is initiated by the action of the steroid hormone ecdysterone. In the work reported here, we studied evolution of this hormone-regulated gene cluster in the melanogaster species subgroup of Drosophila. Genome blot hybridization experiments showed that five other species of this subgroup have DNA sequences that hybridize to D. melanogaster 68C sequences, and that these sequences are divided into a highly conserved region, which does not contain the glue genes, and an extraordinarily diverged region, which does. Molecular cloning of this DNA from D. simulans, D. erecta, D. yakuba, and D. teissieri confirmed the division of the region into a slowly and a rapidly evolving portion, and also showed that the rapidly evolving region of each species codes for third instar larval salivary gland RNAs homologous to the D. melanogaster glue mRNAs. The highly conserved region is at least 13,000 bp long, and is not known to code for any RNAs.
68C胀泡是黑腹果蝇唾液腺多线染色体上一个转录活跃的区域。三类不同的信使核糖核酸起源于胀泡内一个5000碱基对的区域；每一类信使核糖核酸都被翻译成唾液腺胶蛋白sgs - 3、sgs - 7或sgs - 8中的一种。这些信使核糖核酸类别受到协同调控，每种核糖核酸都出现在第三龄幼虫期，并在蛹形成时消失。它们的消失是由类固醇激素蜕皮甾酮的作用引发的。在本文报道的研究中，我们研究了果蝇黑腹果蝇种亚组中这个激素调节基因簇的进化。基因组印迹杂交实验表明，该亚组的其他五个物种具有与黑腹果蝇68C序列杂交的DNA序列，并且这些序列被分为一个高度保守的区域（不包含胶蛋白基因）和一个异常分化的区域（包含胶蛋白基因）。从拟果蝇、直立果蝇、雅库布果蝇和泰斯ieri果蝇中对该DNA进行分子克隆，证实了该区域分为一个进化缓慢和一个进化迅速的部分，并且还表明每个物种进化迅速的区域编码与黑腹果蝇胶蛋白信使核糖核酸同源的第三龄幼虫唾液腺核糖核酸。高度保守的区域至少有13000个碱基对长，目前尚不知道它编码任何核糖核酸。
