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Cyanobacterial symbionts diverged in the late Cretaceous towards lineage-specific nitrogen fixation factories in single-celled phytoplankton

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Item Type:Article
Title:Cyanobacterial symbionts diverged in the late Cretaceous towards lineage-specific nitrogen fixation factories in single-celled phytoplankton
Creators Name:Cornejo-Castillo, F.M. and Cabello, A.M. and Salazar, G. and Sanchez-Baracaldo, P. and Lima-Mendez, G. and Hingamp, P. and Alberti, A. and Sunagawa, S. and Bork, P. and de Vargas, C. and Raes, J. and Bowler, C. and Wincker, P. and Zehr, J.P. and Gasol, J.M. and Massana, R. and Acinas, S.G.
Abstract:The unicellular cyanobacterium UCYN-A, one of the major contributors to nitrogen fixation in the open ocean, lives in symbiosis with single-celled phytoplankton. UCYN-A includes several closely related lineages whose partner fidelity, genome-wide expression and time of evolutionary divergence remain to be resolved. Here we detect and distinguish UCYN-A1 and UCYN-A2 lineages in symbiosis with two distinct prymnesiophyte partners in the South Atlantic Ocean. Both symbiotic systems are lineage specific and differ in the number of UCYN-A cells involved. Our analyses infer a streamlined genome expression towards nitrogen fixation in both UCYN-A lineages. Comparative genomics reveal a strong purifying selection in UCYN-A1 and UCYN-A2 with a diversification process ∼91 Myr ago, in the late Cretaceous, after the low-nutrient regime period occurred during the Jurassic. These findings suggest that UCYN-A diversified in a co-evolutionary process, wherein their prymnesiophyte partners acted as a barrier driving an allopatric speciation of extant UCYN-A lineages.
Keywords:Atlantic Ocean, Biological Evolution, Cyanobacteria, Genomics, Haptophyta, Nitrogen Fixation, Phytoplankton, Seawater, Symbiosis
Source:Nature Communications
ISSN:2041-1723
Publisher:Nature Publishing Group (U.K.)
Volume:7
Page Range:11071
Date:22 March 2016
Official Publication:https://doi.org/10.1038/ncomms11071
PubMed:View item in PubMed

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