Heme pathway evolution in kinetoplastid protists

Background: Kinetoplastea is a diverse protist lineage composed of several of the most successful parasites on Earth, organisms whose metabolisms have coevolved with those of the organisms they infect. Parasitic kinetoplastids have emerged from free-living, non-pathogenic ancestors on multiple occasions during the evolutionary history of the group. Interestingly, in both parasitic and free-living kinetoplastids, the heme pathway—a core metabolic pathway in a wide range of organisms—is incomplete or entirely absent. Indeed, Kinetoplastea investigated thus far seem to bypass the need for heme biosynthesis by acquiring heme or intermediate metabolites directly from their environment. Results: Here we report the existence of a complete heme biosynthetic pathway in Perkinsela spp., kinetoplastids that live as obligate endosymbionts inside amoebozoans belonging to the genus Paramoeba. We also use phylogenetic analysis to infer the evolution of the heme pathway in Kinetoplastea. Conclusion: We...

背景：动质体纲（Kinetoplastea）是一类多样的原生生物谱系，涵盖地球中数种最为成功的寄生生物，其代谢系统与所感染宿主的代谢系统协同演化。在该类群的演化历史中，寄生性动质体曾多次从自由生活、无致病性的祖先类群中独立起源。值得注意的是，无论是寄生性还是自由生活的动质体，血红素合成途径（heme pathway）——一类广泛分布于多种生物中的核心代谢通路——均存在不完整或完全缺失的情况。事实上，目前已被研究的动质体类群似乎均通过直接从环境中获取血红素或其中间代谢产物，来规避自身合成血红素的需求。
结果：本研究报道了Perkinsela属物种中存在完整的血红素生物合成途径；该类动质体作为专性内共生体（obligate endosymbionts），以专性内共生的方式存活于变形虫属（Paramoeba）所属的变形虫类宿主细胞内。本研究同时利用系统发育分析（phylogenetic analysis），推演了动质体纲中血红素合成途径的演化历程。
结论：我们……