• Francisco M Cornejo-Castillo
  • Ana M Cabello
  • Guillem Salazar
  • Patricia Sánchez-Baracaldo
  • Gipsi Lima-Mendez
  • Pascal Hingamp
  • Adriana Alberti
  • Shinichi Sunagawa
  • Peer Bork
  • Colomban de Vargas
  • Jeroen Raes
  • Chris Bowler
  • Patrick Wincker
  • Jonathan P Zehr
  • Josep M Gasol
  • Ramon Massana
  • Silvia G Acinas

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.

Original languageEnglish
Article number11071
Number of pages9
JournalNature Communications
Publication statusPublished - 2016

    Research areas

  • Atlantic Ocean, Biological Evolution, Cyanobacteria, Genomics, Haptophyta, Nitrogen Fixation, Phytoplankton, Seawater, Symbiosis, Research Support, Non-U.S. Gov't

ID: 28366091