Data from: 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 show that Perkinsela spp. is a deep-branching kinetoplastid lineage, and that lateral gene transfer has played a role in the evolution of heme biosynthesis in Perkinsela spp. and other Kinetoplastea. We also discuss the significance of a complete heme pathway in Perkinsela as it relates to its endosymbiotic relationship with Paramoeba.

背景：动质体纲（Kinetoplastea）是一类多样性丰富的原生生物类群，包含地球中数种最为成功的寄生虫，其代谢途径与感染宿主的代谢途径协同演化。在该类群的进化历史中，寄生性动质体曾多次从自由生活、无致病性的祖先类群中演化而来。值得注意的是，无论是寄生还是自由生活的动质体，血红素合成途径（heme pathway）——广泛存在于众多生物中的核心代谢通路——均不完整或完全缺失。截至目前所研究的动质体纲生物，似乎均通过直接从环境中获取血红素或其中间代谢产物，来规避血红素生物合成的需求。
结果：本研究报道了Perkinsela属（Perkinsela spp.）中存在完整的血红素生物合成途径；该类动质体为专性内共生生物，寄生于变形虫属（Paramoeba）所属的变形虫类宿主体内。本研究同时借助系统发育分析（phylogenetic analysis），推断动质体纲内血红素合成途径的演化历程。
结论：本研究证实Perkinsela属属于一支深度分支的动质体纲类群，且水平基因转移（lateral gene transfer）在Perkinsela属及其他动质体纲生物的血红素生物合成演化过程中发挥了重要作用。本研究同时探讨了Perkinsela中完整血红素合成途径的生物学意义，及其与宿主变形虫属的内共生关系之间的关联。