Effects of excess light energy on excitation-energy dynamics in a pennate diatom Phaeodactylum tricornutum

Ryo Nagao, Yoshifumi Ueno, Makio Yokono, Jian Ren Shen, Seiji Akimoto

    Research output: Contribution to journalArticlepeer-review

    10 Citations (Scopus)

    Abstract

    Controlling excitation energy flow is a fundamental ability of photosynthetic organisms to keep a better performance of photosynthesis. Among the organisms, diatoms have unique light-harvesting complexes, fucoxanthin chlorophyll (Chl) a/c-binding proteins. We have recently investigated light-adaptation mechanisms of a marine centric diatom, Chaetoceros gracilis, by spectroscopic techniques. However, it remains unclear how pennate diatoms regulate excitation energy under different growth light conditions. Here, we studied light-adaptation mechanisms in a marine pennate diatom Phaeodactylum tricornutum grown at 30 µmol photons m−2 s−1 and further incubated for 24 h either in the dark, or at 30 or 300 µmol photons m−2 s−1 light intensity, by time-resolved fluorescence (TRF) spectroscopy. The high-light incubated cells showed no detectable oxygen-evolving activity of photosystem II, indicating the occurrence of a severe photodamage. The photodamaged cells showed alterations of steady-state absorption and fluorescence spectra and TRF spectra compared with the dark and low-light adapted cells. In particular, excitation-energy quenching is significantly accelerated in the photodamaged cells as shown by mean lifetime analysis of the Chl fluorescence. These spectral changes by the high-light treatment may result from arrangements of pigment–protein complexes to maintain the photosynthetic performance under excess light illumination. These growth-light dependent spectral properties in P. tricornutum are largely different from those in C. gracilis, thus providing insights into the different light-adaptation mechanisms between the pennate and centric diatoms.

    Original languageEnglish
    Pages (from-to)355-365
    Number of pages11
    JournalPhotosynthesis research
    Volume141
    Issue number3
    DOIs
    Publication statusPublished - Sep 1 2019

    Keywords

    • FCP
    • Low-energy Chl
    • Pennate diatom
    • Photoinhibition
    • Time-resolved fluorescence spectroscopy

    ASJC Scopus subject areas

    • Biochemistry
    • Plant Science
    • Cell Biology

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