端粒复制是链霉菌维持其染色体的线性结构的关键。回文序列是端粒复制重要且必需的序列特征，而目前还没有关于链霉菌非典型端粒复制的必需回文序列的系统报道。前期工作中，本申请者鉴定了卡特利链霉菌DSM46488编码新的非典型端粒系统（端粒-末端蛋白-端粒相关蛋白），并且在多株链霉菌发现了与其同源的非典型端粒系统，包括同源端粒序列（同源性主要集中在前40个核苷酸）及同源Tp-Tap。基于以上结果，本项目将首先鉴定前期识别到的非典型端粒系统是否是各菌株的真正端粒系统。其次，本项目将鉴定它们之间是否存在菌株隔离现象，各元件能否进行互换。最后，系统研究这类同源非典型端粒复制必需回文序列，阐明这类非典型端粒复制机制。前期发现这些编码同源端粒系统的链霉菌编码三种不同遗传结构的Tp-Tap，推测可能代表三个不同进化阶段，因此后续研究中，本申请者将基于本项目的研究结果，对这类Tp-Tap的进化历程进行进一步探索。

Telomere replication is the key for Streptomyces to maintain the linear structure of its chromosomes. The palindromic sequence is an important and essential sequence feature of telomere replication, and there is currently no systematic report on the essential palindromic sequences for Streptomyces non-archetypal telomere replication. In the preliminary work, the applicant identified a novel non-archetypal telomere system (telomere - terminal protein - telomere associated protein, cpTelo-Tpsca-Tapsca) encoded by Streptomyces cattleya DSM46488, and found that several other sequenced Streptomyces encoded homologous non-archetypal systems, including homologous telomere sequences (homology is mainly concentrated in the first 40 nucleotides) and homologous Tp-Tap. Based on the above results, the project will first identify whether the non-archetypal telomere system identified in the previous period is the true telomere system of each strain, respectively. Secondly, this project will identify the existence of “strain isolation phenomenon” among the homologous non-archetypal systems by detecting whether the components can be exchanged. Finally, essential palindrome sequences for homologous non-archetypal telomere replication will be identified to elucidate this type of non-archetypal telomere replication mechanism. It was previously discovered that these Streptomyces encoding homologous non-archetypal telomere systems encode three different genetic structures of Tp - Tap, presumably representing three different evolutionary stages. Therefore, in follow-up studies, the applicant will explore the evolution of the homologous Tp-Tap based on the results of this project.