Early photosynthetic eukaryotes inhabited low-salinity habitats

Patricia Sánchez-Baracaldo (Lead / Corresponding author), John A. Raven, Davide Pisani, Andrew H. Knoll

Research output: Contribution to journalArticle

53 Citations (Scopus)

Abstract

The early evolutionary history of the chloroplast lineage remains an open question. It is widely accepted that the endosymbiosis that established the chloroplast lineage in eukaryotes can be traced back to a single event, in which a cyanobacterium was incorporated into a protistan host. It is still unclear, however, which Cyanobacteria are most closely related to the chloroplast, when the plastid lineage first evolved, and in what habitats this endosymbiotic event occurred. We present phylogenomic and molecular clock analyses, including data from cyanobacterial and chloroplast genomes using a Bayesian approach, with the aim of estimating the age for the primary endosymbiotic event, the ages of crown groups for photosynthetic eukaryotes, and the independent incorporation of a cyanobacterial endosymbiont by Paulinella Our analyses include both broad taxon sampling (119 taxa) and 18 fossil calibrations across all Cyanobacteria and photosynthetic eukaryotes. Phylogenomic analyses support the hypothesis that the chloroplast lineage diverged from its closet relative Gloeomargarita, a basal cyanobacterial lineage, ∼2.1 billion y ago (Bya). Our analyses suggest that the Archaeplastida, consisting of glaucophytes, red algae, green algae, and land plants, share a common ancestor that lived ∼1.9 Bya. Whereas crown group Rhodophyta evolved in the Mesoproterozoic Era (1,600-1,000 Mya), crown groups Chlorophyta and Streptophyta began to radiate early in the Neoproterozoic (1,000-542 Mya). Stochastic mapping analyses indicate that the first endosymbiotic event occurred in low-salinity environments. Both red and green algae colonized marine environments early in their histories, with prasinophyte green phytoplankton diversifying 850-650 Mya.

Original languageEnglish
Pages (from-to)e7737-e7745
Number of pages9
JournalProceedings of the National Academy of Sciences of the United States of America
Volume114
Issue number37
Early online date14 Aug 2017
DOIs
Publication statusPublished - 12 Sep 2017

Fingerprint

Mya
Salinity
Chloroplasts
Eukaryota
Rhodophyta
Chlorophyta
Ecosystem
Cyanobacteria
Crowns
Streptophyta
Chloroplast Genome
Embryophyta
Viridiplantae
Phytoplankton
Plastids
Bayes Theorem
Symbiosis
Calibration
Age Groups
History

Keywords

  • Photosynthetic eukaryotes
  • Chloroplast
  • Cyanobacteria
  • Phylogenomics
  • Relaxed molecular clock

Cite this

Sánchez-Baracaldo, Patricia ; Raven, John A. ; Pisani, Davide ; Knoll, Andrew H. / Early photosynthetic eukaryotes inhabited low-salinity habitats. In: Proceedings of the National Academy of Sciences of the United States of America. 2017 ; Vol. 114, No. 37. pp. e7737-e7745.
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Early photosynthetic eukaryotes inhabited low-salinity habitats. / Sánchez-Baracaldo, Patricia (Lead / Corresponding author); Raven, John A.; Pisani, Davide; Knoll, Andrew H.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 114, No. 37, 12.09.2017, p. e7737-e7745.

Research output: Contribution to journalArticle

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T1 - Early photosynthetic eukaryotes inhabited low-salinity habitats

AU - Sánchez-Baracaldo, Patricia

AU - Raven, John A.

AU - Pisani, Davide

AU - Knoll, Andrew H.

N1 - D.P. was supported by Natural Environment Research Council, Biosphere Evolution, Transitions, and Resilience Grant NE/P013643/1 and Templeton Foundation Grant 60579. A.H.K. acknowledges support from the NASA Astrobiology Institute.

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AB - The early evolutionary history of the chloroplast lineage remains an open question. It is widely accepted that the endosymbiosis that established the chloroplast lineage in eukaryotes can be traced back to a single event, in which a cyanobacterium was incorporated into a protistan host. It is still unclear, however, which Cyanobacteria are most closely related to the chloroplast, when the plastid lineage first evolved, and in what habitats this endosymbiotic event occurred. We present phylogenomic and molecular clock analyses, including data from cyanobacterial and chloroplast genomes using a Bayesian approach, with the aim of estimating the age for the primary endosymbiotic event, the ages of crown groups for photosynthetic eukaryotes, and the independent incorporation of a cyanobacterial endosymbiont by Paulinella Our analyses include both broad taxon sampling (119 taxa) and 18 fossil calibrations across all Cyanobacteria and photosynthetic eukaryotes. Phylogenomic analyses support the hypothesis that the chloroplast lineage diverged from its closet relative Gloeomargarita, a basal cyanobacterial lineage, ∼2.1 billion y ago (Bya). Our analyses suggest that the Archaeplastida, consisting of glaucophytes, red algae, green algae, and land plants, share a common ancestor that lived ∼1.9 Bya. Whereas crown group Rhodophyta evolved in the Mesoproterozoic Era (1,600-1,000 Mya), crown groups Chlorophyta and Streptophyta began to radiate early in the Neoproterozoic (1,000-542 Mya). Stochastic mapping analyses indicate that the first endosymbiotic event occurred in low-salinity environments. Both red and green algae colonized marine environments early in their histories, with prasinophyte green phytoplankton diversifying 850-650 Mya.

KW - Photosynthetic eukaryotes

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KW - Phylogenomics

KW - Relaxed molecular clock

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DO - 10.1073/pnas.1620089114

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