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

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...

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Bibliographic Details
Published in:Nature Communications
Main Authors: Cornejo-Castillo, Francisco M., Cabello, Ana M., Salazar, Guillem, Sánchez-Baracaldo, Patricia, Lima-Mendez, Gipsi, Hingamp, Pascal, Alberti, Adriana, Sunagawa, Shinichi, Bork, Peer, De Vargas, Colomban, Raes, Jeroen, Bowler, Chris, Wincker, Patrick, Zehr, Jonathan P., Gasol, Josep M., Massana, Ramon, Acinas, Silvia G.
Format: Article in Journal/Newspaper
Language:English
Published: 2016
Subjects:
South Atlantic Ocean
Online Access:https://hdl.handle.net/1983/3dd3a633-16e3-44f2-ba42-33d71f6236a3
https://research-information.bris.ac.uk/en/publications/3dd3a633-16e3-44f2-ba42-33d71f6236a3
https://doi.org/10.1038/ncomms11071
https://research-information.bris.ac.uk/ws/files/88557076/ncomms11071.pdf
https://research-information.bris.ac.uk/ws/files/88557078/ncomms11071_s1.pdf
http://www.scopus.com/inward/record.url?scp=84961658202&partnerID=8YFLogxK
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Summary: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.

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