The phylum Cyanobacteria includes free-living bacteria and plastids, the descendants of cyanobacteria that were engulfed by the ancestral lineage of the major photosynthetic eukaryotic group Archaeplastida. Endosymbiotic events that followed this primary endosymbiosis spread plastids across diverse eukaryotic groups. The remnants of the ancestral cyanobacterial genome present in all modern plastids, enable the placement of plastids within Cyanobacteria using sequence-based phylogenetic analyses. To date, such phylogenetic studies have produced conflicting results and two competing hypotheses: (1) plastids diverge relatively recently in cyanobacterial evolution and are most closely related to nitrogen-fixing cyanobacteria, or (2) plastids diverge early in the evolutionary history of cyanobacteria, before the divergence of most cyanobacterial lineages. Here, we use phylogenetic analysis of ribosomal proteins from an expanded data set of cyanobacterial and representative plastid genomes to infer a deep placement for the divergence of the plastid ancestor lineage. We recover plastids as sister to Gloeomargarita and show that the group diverges from other cyanobacterial groups before Pseudanabaena, a previously unreported placement. The tree topologies and phylogenetic distances in our study have implications for future molecular clock studies that aim to model accurate divergence times, especially with respect to groups containing fossil calibrations. The newly sequenced cyanobacterial groups included here will also enable the use of novel cyanobacterial microfossil calibrations.
Keywords: Archaeplastida; chloroplast; cyanobacteria; evolution; phylogenetic tree.
An Early-Branching Freshwater Cyanobacterium at the Origin of Plastids.Curr Biol. 2017 Feb 6;27(3):386-391. doi: 10.1016/j.cub.2016.11.056. Epub 2017 Jan 26. Curr Biol. 2017. PMID: 28132810 Free PMC article.
Early photosynthetic eukaryotes inhabited low-salinity habitats.Proc Natl Acad Sci U S A. 2017 Sep 12;114(37):E7737-E7745. doi: 10.1073/pnas.1620089114. Epub 2017 Aug 14. Proc Natl Acad Sci U S A. 2017. PMID: 28808007 Free PMC article.
Genes of cyanobacterial origin in plant nuclear genomes point to a heterocyst-forming plastid ancestor.Mol Biol Evol. 2008 Apr;25(4):748-61. doi: 10.1093/molbev/msn022. Epub 2008 Jan 24. Mol Biol Evol. 2008. PMID: 18222943
A new scenario of plastid evolution: plastid primary endosymbiosis before the divergence of the "Plantae," emended.J Plant Res. 2005 Aug;118(4):247-55. doi: 10.1007/s10265-005-0219-1. Epub 2005 Jul 20. J Plant Res. 2005. PMID: 16032387 Review.
Horizontal and endosymbiotic gene transfer in early plastid evolution.New Phytol. 2019 Oct;224(2):618-624. doi: 10.1111/nph.15965. Epub 2019 Jul 4. New Phytol. 2019. PMID: 31135958 Review.
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Blue-/Green-Light-Responsive Cyanobacteriochromes Are Cell Shade Sensors in Red-Light Replete Niches.iScience. 2020 Mar 27;23(3):100936. doi: 10.1016/j.isci.2020.100936. Epub 2020 Feb 25. iScience. 2020. PMID: 32146329 Free PMC article.