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：动质体目（Kinetoplastea）是一类多样性丰富的原生生物演化支，包含地球上数种最为成功的寄生虫类群。该类群生物的代谢途径与其侵染宿主的代谢途径协同演化。在该类群的演化历程中，寄生性动质体曾多次从自由生活的非致病性祖先类群中独立起源。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）——一类广泛分布于多种生物中的核心代谢通路——均不完整甚至完全缺失。截至目前已被研究的动质体类群，似乎均通过直接从环境中摄取血红素或中间代谢产物，来规避血红素生物合成的需求。结果：本研究报道了珀金斯拉虫属（Perkinsela spp.）中存在完整的血红素生物合成途径，该类群为专性内生于变形巴虫属（Paramoeba）所属变形虫类（amoebozoans）体内的动质体。本研究同时通过系统发育分析，推演了动质体目中血红素合成途径的演化过程。结论：本研究证实，珀金斯拉虫属为一支深分支的动质体演化支，且水平基因转移（lateral gene transfer）在珀金斯拉虫属及其他动质体类群的血红素生物合成途径演化中发挥了重要作用。本研究还探讨了珀金斯拉虫属完整血红素合成途径的生物学意义，及其与变形巴虫属之间的内共生关系的关联。