席藻ITS序列拷贝类型及进化关系分析

由于协同进化未完成,蓝藻的16S-23S rDNA基因间隔序列(ITS)存在多种拷贝类型,目前蓝藻ITS序列的拷贝类型分布以及演化规律尚未研究清楚。该文采用本地采集的席藻属样品,测定其ITS序列,并结合基因库中已有的席藻ITS序列,对席藻属蓝藻ITS序列拷贝类型及其之间的进化关系进行探讨。结果显示,席藻属ITS序列的PCR产物有两种情况,即单一条带(仅出现ITS-IA或ITS-I型)和两条条带(同时出现ITS-IA和ITS-N型),其中以单一条带的ITS-IA型最为普遍;在基于ITS序列的系统发生树中,ITS-IA型和ITS-I型均各自聚为一个组群,且ITS-IA型的组群节点出现较早,表明席藻属ITS-I型极有可能是由其原来的ITS-IA型缺失tRNAAla编码区进化而来,ITS-IA型应为席藻ITS序列的基本结构。

Analyses on the types of copy and evolutionary relationships of ITS sequence of Phormidium

The coevolution of the ITS sequences hasn''t been fully accomplished leading to multiple types of copy in cyanobacteria,while the distribution rule of ITS copy in cyanobacteria are unclear. We used Phormidium strains picked up from Suzhou districts and 12 other strains selected from Genebank as the materials to study the characteristics and the evolutionary relationships among different types of copy. The results showed that the PCR product of ITS of Phormidium had single band(i. e. ITS-IA type or ITS-I type)or two bands(i. e. ITS-IA and ITS-N type),and ITS-IA was the most popular type in the materials used in this study; the phylogeny analyzed results indicated that ITS-IA type and ITS-I type were distributed in different groups respectively,and the ITS-IA group appeared earlier than ITS-I group. Thus we proved that ITS-I type was evolved from a deletion of tRNA^Ala coding region of ITS-IA type,and ITS-IA type should be the basic structure of ITS copy of Phormidium.