Light dependent accumulation of β-carotene enhances photo-acclimation of Euglena gracilis

Yuri Tanno, Shota Kato, Senji Takahashi, Shun Tamaki, Shinichi Takaichi, Yutaka Kodama, Kintake Sonoike, Tomoko Shinomura*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


Carotenoids are essential components of photosynthetic organisms including land plants, algae, cyanobacteria, and photosynthetic bacteria. Although the light-mediated regulation of carotenoid biosynthesis, including the light/dark cycle as well as the dependence of carotenoid biosynthesis–related gene translation on light wavelength, has been investigated in land plants, these aspects have not been studied in microalgae. Here, we investigated carotenoid biosynthesis in Euglena gracilis and found that zeaxanthin accumulates in the dark. The major carotenoid species in E. gracilis, namely β-carotene, neoxanthin, diadinoxanthin and diatoxanthin, accumulated corresponding to the duration of light irradiation under the light/dark cycle, although the translation of carotenoid biosynthesis genes hardly changed. Irradiation with either blue or red-light (3 μmol photons m−2 s−1) caused a 1.3-fold increase in β-carotene content compared with the dark control. Blue-light irradiation (300 μmol photons m−2 s−1) caused an increase in the cellular content of both zeaxanthin and all trans-diatoxanthin, and this increase was proportional to blue-light intensity. In addition, pre-irradiation with blue-light of 3 or 30 μmol photons m−2 s−1 enhanced the photosynthetic activity and tolerance to high-light stress. These findings suggest that the accumulation of β-carotene is regulated by the intensity of light, which may contribute to the acclimation of E. gracilis to the light environment in day night conditions.

Original languageEnglish
Article number111950
JournalJournal of Photochemistry and Photobiology B: Biology
Publication statusPublished - 2020 Aug


  • Blue light
  • Carotenoid
  • Photo-acclimation
  • Photosynthesis
  • Red light

ASJC Scopus subject areas

  • Radiation
  • Radiological and Ultrasound Technology
  • Biophysics
  • Radiology Nuclear Medicine and imaging


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