title: Life-cycle modification in open oceans accounts for genome variability in a cosmopolitan phytoplankton.
abstract: Emiliania huxleyi is the most abundant calcifying plankton in modern oceans with substantial intraspecific genome variability and a biphasic life cycle involving sexual alternation between calcified 2N and flagellated 1N cells. We show that high genome content variability in Emiliania relates to erosion of 1N-specific genes and loss of the ability to form flagellated cells. Analysis of 185 E. huxleyi strains isolated from world oceans suggests that loss of flagella occurred independently in lineages inhabiting oligotrophic open oceans over short evolutionary timescales. This environmentally linked physiogenomic change suggests life cycling is not advantageous in very large/diluted populations experiencing low biotic pressure and low ecological variability. Gene loss did not appear to reflect pressure for genome streamlining in oligotrophic oceans as previously observed in picoplankton. Life-cycle modifications might be common in plankton and cause major functional variability to be hidden from traditional taxonomic or molecular markers.
authors.affiliation: 1] Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile [2] UMI 3614, Evolutionary Biology and Ecology of Algae, CNRS, UPMC Sorbonne Universités, PUCCh, UACH, Station Biologique de Roscoff, Roscoff, France [3] Instituto Milenio de Oceanografía, Concepción, Chile [4] CNRS UMR 7144 and UMPC, Evolution of Pelagic Ecosystems and Protists (EPEP), CNRS, UPMC, Station Biologique de Roscoff, Roscoff, France.
authors.forename: Peter
authors.initials: P
authors.lastname: von Dassow
authors.affiliation: Alfred Wegener Institute Helmhotz Centre for Polar and Marine Research, Bremerhaven, Germany.
authors.forename: Uwe
authors.initials: U
authors.lastname: John
authors.affiliation: 1] Institute for Chemical Research, Kyoto University, Kyoto, Japan [2] CNRS, Aix-Marseille Université, Laboratoire Information Génomique et Structurale (UMR 7256), Mediterranean Institute of Microbiology (FR 3479), Marseille, France.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ogata
authors.affiliation: CNRS-UMPC, FR2424, Roscoff Culture Collection, Station Biologique de Roscoff, Roscoff, France.
authors.forename: Ian
authors.initials: I
authors.lastname: Probert
authors.affiliation: Marine Biological Association of the UK, The Laboratory, Citadel Hill, Plymouth, UK.
authors.forename: El Mahdi
authors.initials: el M
authors.lastname: Bendif
authors.affiliation: Alfred Wegener Institute Helmhotz Centre for Polar and Marine Research, Bremerhaven, Germany.
authors.forename: Jessica U
authors.initials: JU
authors.lastname: Kegel
authors.affiliation: CNRS UMR 7144 and UMPC, Evolution of Pelagic Ecosystems and Protists (EPEP), CNRS, UPMC, Station Biologique de Roscoff, Roscoff, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Audic
authors.affiliation: CEA Genoscope, 2 rue Gaston Crémieux, Evry, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Wincker
authors.affiliation: CEA Genoscope, 2 rue Gaston Crémieux, Evry, France.
authors.forename: Corinne
authors.initials: C
authors.lastname: Da Silva
authors.affiliation: CNRS, Aix-Marseille Université, Laboratoire Information Génomique et Structurale (UMR 7256), Mediterranean Institute of Microbiology (FR 3479), Marseille, France.
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Claverie
authors.affiliation: Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Doney
authors.affiliation: Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Glover
authors.affiliation: 1] Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile [2] UMI 3614, Evolutionary Biology and Ecology of Algae, CNRS, UPMC Sorbonne Universités, PUCCh, UACH, Station Biologique de Roscoff, Roscoff, France.
authors.forename: Daniella Mella
authors.initials: DM
authors.lastname: Flores
authors.affiliation: Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Yeritza
authors.initials: Y
authors.lastname: Herrera
authors.affiliation: CNRS, Aix-Marseille Université, Laboratoire Information Génomique et Structurale (UMR 7256), Mediterranean Institute of Microbiology (FR 3479), Marseille, France.
authors.forename: Magali
authors.initials: M
authors.lastname: Lescot
authors.affiliation: CNRS UMR 7144 and UMPC, Evolution of Pelagic Ecosystems and Protists (EPEP), CNRS, UPMC, Station Biologique de Roscoff, Roscoff, France.
authors.forename: Marie-José
authors.initials: MJ
authors.lastname: Garet-Delmas
authors.affiliation: CNRS UMR 7144 and UMPC, Evolution of Pelagic Ecosystems and Protists (EPEP), CNRS, UPMC, Station Biologique de Roscoff, Roscoff, France.
authors.forename: Colomban
authors.initials: C
authors.lastname: de Vargas
mesh_terms: D000818:Animals; D018533:Biomass; D002734:Chlorophyll / Q000737:chemistry; D019295:Computational Biology; D004171:Diploidy; D004463:Ecology; D005407:Flagella / Q000378:metabolism; D020869:Gene Expression Profiling; D005819:Genetic Markers / Q000235:genetics; D016678:Genome; D023281:Genomics; D005838:Genotype; D058087:Haptophyta / Q000235:genetics*; D008018:Life Cycle Stages; D009792:Oceans and Seas; D010839:Phytoplankton / Q000235:genetics*
chemical_list: D005819:Genetic Markers; D002734:Chlorophyll