Did an ancient chlamydial endosymbiosis facilitate the establishment of primary plastids?
Did an ancient chlamydial endosymbiosis facilitate the establishment of primary plastids?
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DOI：
10.1186/gb-2007-8-6-r99
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发表时间：
2007
期刊：
影响因子：
12.3
通讯作者：
Gogarten JP
中科院分区：
文献类型：
--
作者：
Huang J;Gogarten JP
对红藻merolae的系统基因组分析表明，至少有21个基因在衣原体和原生光合真核生物之间转移，表明衣原体与原生光合真核生物存在一种古老的内共生关系。古老的内共生关系负责线粒体和质体的起源，它们有助于几个主要真核生物群体的分化。尽管在植物中没有发现衣原体这种专性细胞内细菌，但出人意料的是，许多衣原体基因与植物同源物最为相似，有趣的是，这些基因通常含有质体靶向信号。这一观察结果引发了几个假设，包括衣原体和植物相关群体之间的基因转移以及衣原体和蓝藻之间的祖先关系。我们对红藻merolae进行了系统基因组分析，以确定衣原体同源物特异性相关基因。我们发现至少有21个基因在衣原体和初级光合真核生物之间转移，其中供体与环境原衣原体最相似。如此高数量的转移基因表明古代衣原体与原始光合真核生物存在内共生关系。我们假设有三种生物参与了初级光合谱系的建立：真核宿主细胞、提供光合能力的蓝藻内共生体和促进蓝藻内共生体建立的衣原体内共生体或寄生虫。我们的研究结果为在质体和宿主细胞质之间建立初级内共生关系所必需的复杂相互作用提供了一瞥，从而解释了在异养生物和光自养生物之间建立长期成功的内共生关系的罕见性。我们的数据还为所有初级光合真核生物及其所含质体的共同起源提供了强有力的独立支持。
Phylogenomic analyses of the red alga Cyanidioschyzon merolae shows that at least 21 genes were transferred between chlamydiae and primary photosynthetic eukaryotes, suggesting an ancient chlamydial endosymbiosis with the ancestral primary photosynthetic eukaryote. Ancient endosymbioses are responsible for the origins of mitochondria and plastids, and they contribute to the divergence of several major eukaryotic groups. Although chlamydiae, a group of obligate intracellular bacteria, are not found in plants, an unexpected number of chlamydial genes are most similar to plant homologs, which, interestingly, often contain a plastid-targeting signal. This observation has prompted several hypotheses, including gene transfer between chlamydiae and plant-related groups and an ancestral relationship between chlamydiae and cyanobacteria. We conducted phylogenomic analyses of the red alga Cyanidioschyzon merolae to identify genes specifically related to chlamydial homologs. We show that at least 21 genes were transferred between chlamydiae and primary photosynthetic eukaryotes, with the donor most similar to the environmental Protochlamydia. Such an unusually high number of transferred genes suggests an ancient chlamydial endosymbiosis with the ancestral primary photosynthetic eukaryote. We hypothesize that three organisms were involved in establishing the primary photosynthetic lineage: the eukaryotic host cell, the cyanobacterial endosymbiont that provided photosynthetic capability, and a chlamydial endosymbiont or parasite that facilitated the establishment of the cyanobacterial endosymbiont. Our findings provide a glimpse into the complex interactions that were necessary to establish the primary endosymbiotic relationship between plastid and host cytoplasms, and thereby explain the rarity with which long-term successful endosymbiotic relationships between heterotrophs and photoautotrophs were established. Our data also provide strong and independent support for a common origin of all primary photosynthetic eukaryotes and of the plastids they harbor.
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影响因子：
4
作者：
GRAY, MW
通讯作者：
GRAY, MW
影响因子：
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作者：
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通讯作者：
Golding, GB
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通讯作者：
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