Characterization of photosystem I antenna proteins in the prasinophyte Ostreococcus tauri

Wesley D. Swingley, Masakazu Iwai, Yang Chen, Shin ichiro Ozawa, Kenji Takizawa, Yuichiro Takahashi, Jun Minagawa

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)

Abstract

Prasinophyceae are a broad class of early-branching eukaryotic green algae. These picophytoplankton are found ubiquitously throughout the ocean and contribute considerably to global carbon-fixation. Ostreococcus tauri, as the first sequenced prasinophyte, is a model species for studying the functional evolution of light-harvesting systems in photosynthetic eukaryotes. In this study we isolated and characterized O. tauri pigment-protein complexes. Two photosystem I (PSI) fractions were obtained by sucrose density gradient centrifugation in addition to free light-harvesting complex (LHC) fraction and photosystem II (PSII) core fractions. The smaller PSI fraction contains the PSI core proteins, LHCI, which are conserved in all green plants, Lhcp1, a prasinophyte-specific LHC protein, and the minor, monomeric LHCII proteins CP26 and CP29. The larger PSI fraction contained the same antenna proteins as the smaller, with the addition of Lhca6 and Lhcp2, and a 30% larger absorption cross-section. When O. tauri was grown under high-light conditions, only the smaller PSI fraction was present. The two PSI preparations were also found to be devoid of the far-red chlorophyll fluorescence (715-730. nm), a signature of PSI in oxygenic phototrophs. These unique features of O. tauri PSI may reflect primitive light-harvesting systems in green plants and their adaptation to marine ecosystems. Possible implications for the evolution of the LHC-superfamily in photosynthetic eukaryotes are discussed.

Original languageEnglish
Pages (from-to)1458-1464
Number of pages7
JournalBiochimica et Biophysica Acta - Bioenergetics
Volume1797
Issue number8
DOIs
Publication statusPublished - Aug 2010

Keywords

  • Evolution
  • Light-harvesting complex
  • Photosystem I
  • Prasinophytes

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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