Global diversity and distribution of close relatives of apicomplexan parasites
Global diversity and distribution of close relatives of apicomplexan parasites
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DOI：
10.1111/1462-2920.14134
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发表时间：
2018-08-01
影响因子：
5.1
通讯作者：
Keeling, Patrick J.
中科院分区：
文献类型：
--
作者：
Mathur, Varsha;del Campo, Javier;Keeling, Patrick J.
顶复门是一组专性细胞内寄生虫，但它们保留的残余非光合质体揭示了它们是从自由生活的光合祖先进化而来的。顶复门的近亲包括光合色藻（例如，Chromera和Vitrella），非光合作用的阴道虫捕食者（例如，Colpodella）和几个环境分支统称为顶复门相关谱系（ARLs）。在这里，我们调查的全球分布和推断生态的ARLs广泛寻找apicomplexan相关的质体小核糖体亚基（SSU）基因在大规模的高通量细菌扩增子调查。从全球224个地理位置搜索超过2.2亿个序列，发现94324个ARL质体SSU序列。荟萃分析证实，所有的ARLs都与珊瑚礁有关，而不是一般的海洋环境，但只有一个子集实际上与珊瑚本身有关。最出乎意料的是，Chromera只在珊瑚生物沉积物中发现，而不是在珊瑚组织中，这表明它不是通常认为的珊瑚共生体。相比之下，ARL-V是所有ARL分支中最多样化，地理分布最广和最丰富的分支，并且与珊瑚组织和粘液严格相关。在珊瑚礁中的19种珊瑚物种中发现了ARL-V，包括深度超过500米的偶氮黄藻珊瑚。我们认为，这是一个寄生或寄生的关系，而不是光合共生，进一步强调隔离ARL-V和确定其与珊瑚宿主的关系的重要性。
Apicomplexans are a group of obligate intracellular parasites, but their retention of a relict non-photosynthetic plastid reveals that they evolved from free-living photosynthetic ancestors. The closest relatives of apicomplexans include photosynthetic chromerid algae (e.g., Chromera and Vitrella), non-photosynthetic colpodellid predators (e.g., Colpodella) and several environmental clades collectively called Apicomplexan-Related Lineages (ARLs). Here we investigate the global distribution and inferred ecology of the ARLs by expansively searching for apicomplexan-related plastid small ribosomal subunit (SSU) genes in large-scale high-throughput bacterial amplicon surveys. Searching more than 220 million sequences from 224 geographical sites worldwide revealed 94324 ARL plastid SSU sequences. Meta-analyses confirm that all ARLs are coral reef associated and not to marine environments generally, but only a subset is actually associated with coral itself. Most unexpectedly, Chromera was found exclusively in coral biogenous sediments, and not within coral tissue, indicating that it is not a coral symbiont, as typically thought. In contrast, ARL-V is the most diverse, geographically widespread and abundant of all ARL clades and is strictly associated with coral tissue and mucus. ARL-V was found in 19 coral species in reefs, including azooxanthellate corals at depths greater than 500 m. We suggest this is indicative of a parasitic or commensal relationship, and not of photosynthetic symbiosis, further underscoring the importance of isolating ARL-V and determining its relationship with the coral host.