舌鳎亚科鱼类线粒体控制区快速进化及其重复序列延伸机制初步研究

Preliminary Study on the Rapid Evolution of MtDNA Control Region and the Elongated Mechanism of Tandem Repeat Units in Cynoglossinae Fishes

本研究测定双线舌鳎Cynoglossus bilineatus(Lacepède,1802)、长钩须鳎Paraplagusia bilineata(Bloch,1787)和短钩须鳎Paraplagusia blochii(Bleeker,1851)3种舌鳎亚科鱼类的线粒体(mtDNA)控制区全序列,并与舌鳎亚科其它4种及鲽形目其他科的5种鱼类mtDNA控制区结构和序列进行了比较分析。结果显示,3种舌鳎鱼类的线粒体控制区全长从655～1 155bp,长度差异明显;舌鳎亚科鱼类控制区结构与其他鲽形目鱼类相似性很低,保守区系列中只能识别出CSB-A和TAS。碱基组成比较发现这3种舌鳎鱼类的AT含量比鲽形目其它鱼类要高。分析认为上述事件可能都是由该类群鱼类控制区的快速进化导致的。所有3种舌鳎的控制区在5’端都存在串联重复序列,每个重复单元中都存在类似于TAS的相关序列,并且重复序列可以形成非常稳定的二级结构。这2种特征为形成线粒体重复序列的非正常延伸机制(Illegitimate elongation model)提供了新的证据,同时,推测了这些舌鳎鱼类重复序列可能的延伸过程。

The complete control regions of mitochondrial DNA were amplified in three tongue soles Cynoglossus bilineatus（Lacepède,1802）,Paraplagusia bilineata（Bloch,1787）,and Paraplagusia blochii（Bleeker,1851） from subfamily Cynoglossinae,and compared with that from other four flatfishes.The length of control regions（CR） ranged from 655 to 1155 bp and exhibited apparent length heteroplasmy.Comparisons showed that the control regions have significant differences from that of other flatfishes,with only conserved blocks of CSB-A and TAS identified and higher AT content detected.It was presumed that these variations may have resulted in the fast evolution of CR regions in these tongue soles.Furthermore,the presence of tandem repeats at 5’ end of control regions was detected,and these repeat units bear TAS-like sequences,which the possess capability of forming the stable secondary structure in all three tongue soles.These characteristics of control regions in those soles provide likely new evidences for the illegitimate elongation model,the elongated mechanism of tandem repeat units.Additionally,the elongation process of these tandem repeats in tongue soles was speculated using illegitimate elongation model.