The single, ancient origin of chromist plastids

Hwan Su Yoon, Jeremiah D. Hackett, Gabriele Pinto, Debashish Bhattacharya

Research output: Contribution to journalArticlepeer-review

315 Scopus citations


Algae include a diverse array of photosynthetic eukaryotes excluding land plants. Explaining the origin of algal plastids continues to be a major challenge in evolutionary biology. Current knowledge suggests that plastid primary endosymbiosis, in which a single-celled protist engulfs and "enslaves" a cyanobacterium, likely occurred once and resulted in the primordial alga. This eukaryote then gave rise through vertical evolution to the red, green, and glaucophyte algae. However, some modern algal lineages have a more complicated evolutionary history involving a secondary endosymbiotic event, in which a protist engulfed an existing eukaryotic alga (rather than a cyanobacterium), which was then reduced to a secondary plastid. Secondary endosymbiosis explains the majority of algal biodiversity, yet the number and timing of these events is unresolved. Here we analyzed a five-gene plastid data set to show that a taxonomically diverse group of chlorophyll c2-containing protists comprising cryptophyte, haptophyte, and stramenopiles algae (Chromista) share a common plastid that most likely arose from a single, ancient (≈1,260 million years ago) secondary endosymbiosis involving a red alga. This finding is consistent with Chromista monophyly and implicates secondary endosymbiosis as an important force in generating eukaryotic biodiversity.

Original languageEnglish (US)
Pages (from-to)15507-15512
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number24
StatePublished - Nov 26 2002


  • Cryptophyte
  • Haptophyte
  • Plastid evolution
  • Secondary endosymbiosis
  • Stramenopiles

ASJC Scopus subject areas

  • General


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