BLASTn results.

Trypanosoma lainsoni, Trypanosoma platydactyli, and Trypanosoma scelopori are kinetoplastid flagellates belonging to the LSRM clade of the genus Trypanosoma. These parasites have a unique mitochondrial DNA structure, the kinetoplast, comprising catenated maxicircles and minicircles. However, genetic information on the kinetoplasts of these species remains unknown. In this study, we assembled and analyzed maxicircles from different isolates of T. lainsoni, T. platydactyli, and T. scelopori to address the current gap in genetic information about the LSRM clade and explore their phylogenetic relationships within the Trypanosoma genus. The maxicircle of T. lainsoni isolate Le29, including the coding and divergent regions, was de novo assembled combining Illumina and Oxford Nanopore Technologies, revealing a length of 49,306 bp. Additional isolates of T. lainsoni (Ca37 and Ca47), as well as T. platydactyli and T. scelopori, were sequenced with Illumina, yielding complete coding regions and partial divergent regions for all. As in other trypanosomes, coding regions exhibited conserved synteny in gene order and RNA editing patterns. We found that mRNA editing by U-insertion was higher in T. lainsoni than in T. cruzi, suggesting a partial loss of editing in the latter. Phylogenetic analyses based on the coding region positioned the LSRM clade alongside the Aquatic clade as one of the most ancestral groups within non-salivarian trypanosomes and supported the ancestral position of the Trypanosoma brucei clade, contrasting with previous reports. Finally, analysis of the maxicircle divergent region suggests a gradual transition from long to short repeat structures in non-salivarian trypanosomes. This study provides the first characterization of the T. lainsoni maxicircle and related LSRM clade species. These findings provide new insights into the ancestral relationships within the group, the evolution of the divergent region of the maxicircles and propose RNA editing has been evolving within the genus.

兰森锥虫（Trypanosoma lainsoni）、平趾锥虫（Trypanosoma platydactyli）和棘鳞蜥锥虫（Trypanosoma scelopori）均属于锥虫属（Trypanosoma）LSRM支（LSRM clade）的动基体目鞭毛虫（kinetoplastid flagellates）。这类寄生虫拥有独特的线粒体DNA结构——动基体（kinetoplast），由连环状大环DNA（catenated maxicircles）和小环DNA（minicircles）组成。然而，目前关于这些物种动基体的遗传信息仍属空白。
本研究对兰森锥虫、平趾锥虫和棘鳞蜥锥虫不同分离株的大环DNA进行了组装与分析，以期填补LSRM支遗传信息的现有缺口，并探究其在锥虫属内的系统发育关系。
结合Illumina与牛津纳米孔测序技术（Oxford Nanopore Technologies），我们从头组装了兰森锥虫Le29分离株的大环DNA（包含编码区与差异区），其全长为49306 bp。我们采用Illumina测序对兰森锥虫的另外两个分离株（Ca37与Ca47）以及平趾锥虫、棘鳞蜥锥虫进行了测序，获得了所有受试物种的完整编码区与部分差异区序列。
与其他锥虫类似，这些编码区在基因共线性与RNA编辑（RNA editing）模式上均呈现保守性。我们发现，兰森锥虫的U插入型mRNA编辑水平高于克氏锥虫（Trypanosoma cruzi），这提示后者的RNA编辑过程存在部分缺失。
基于编码区的系统发育分析显示，LSRM支与水生支（Aquatic clade）一同构成了非唾液传播型锥虫（non-salivarian trypanosomes）中最为古老的类群之一，同时证实了布氏锥虫支（Trypanosoma brucei clade）的祖先地位，这与既往研究结论相悖。
最后，对大环DNA差异区的分析表明，非唾液传播型锥虫的差异区存在从长重复结构向短重复结构逐步过渡的演化特征。
本研究首次完成了兰森锥虫及其相关LSRM支物种的大环DNA解析。本研究结果为该类群的祖先亲缘关系、大环DNA差异区的演化提供了新见解，并提出锥虫属内的RNA编辑过程存在动态演化。