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

Cornejo-Castillo, F.M.; Cabello, A.M.; Salazar, G.; Sanchez-Baracaldo, P.; Lima-Mendez, G.; Hingamp, P.; Alberti, A.; Sunagawa, S.; Bork, P.; de Vargas, C.; Raes, J.; Bowler, C.; Wincker, P.; Zehr, J.P.; Gasol, J.M.; Massana, R.; Acinas, S.G.

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., Cabello, A.M., Salazar, G., Sanchez-Baracaldo, P., Lima-Mendez, G., Hingamp, P., Alberti, A., Sunagawa, S., Bork, P., de Vargas, C., Raes, J., Bowler, C., Wincker, P., Zehr, J.P., Gasol, J.M., 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
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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