Did an ancient chlamydial endosymbiosis facilitate the establishment of primary plastids?


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dc.contributor.author Huang, Jinling
dc.contributor.author Gogarten, Johann Peter
dc.date.accessioned 2007-10-15T19:55:58Z
dc.date.available 2007-10-15T19:55:58Z
dc.date.issued 2007-06-04
dc.identifier.citation Genome Biology 8 (2007): R99 en
dc.identifier.uri http://hdl.handle.net/1912/1820
dc.description © 2007 Huang and Gogarten. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The definitive version was published in Genome Biology 8 (2007): R99, doi:10.1186/gb-2007-8-6-r99. en
dc.description.abstract 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. en
dc.description.sponsorship This work was performed while JH held a National Research Council Associateship Award at the NASA Astrobiology Institute at the Marine Biological Laboratory in Woods Hole, Massachusetts (NCC2-1054). Additional support was provided through NSF (MCB-0237197) and NASA AISR (NNG04GP90G) grants to JPG. en
dc.format.mimetype application/pdf
dc.language.iso en en
dc.publisher BioMed Central en
dc.relation.uri http://dx.doi.org/10.1186/gb-2007-8-6-r99
dc.rights.uri http://creativecommons.org/licenses/by/2.0 *
dc.title Did an ancient chlamydial endosymbiosis facilitate the establishment of primary plastids? en
dc.type Article en
dc.identifier.doi 10.1186/gb-2007-8-6-r99

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