Enhancement of excitation-energy quenching in fucoxanthin chlorophyll a/c-binding proteins isolated from a diatom Phaeodactylum tricornutum upon excess-light illumination.

Affiliation

Nagao R(1), Yokono M(2), Ueno Y(3), Suzuki T(4), Kumazawa M(5), Kato KH(6), Tsuboshita N(6), Dohmae N(4), Ifuku K(5), Shen JR(6), Akimoto S(7).
Author information:
(1)Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan. Electronic address: [Email]
(2)Institute of Low Temperature Science, Hokkaido University, Hokkaido 060-0819, Japan.
(3)Graduate School of Science, Kobe University, Hyogo 657-8501, Japan.
(4)Biomolecular Characterization Unit, RIKEN Center for Sustainable Resource Science, Saitama 351-0198, Japan.
(5)Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
(6)Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan.
(7)Graduate School of Science, Kobe University, Hyogo 657-8501, Japan. Electronic address: [Email]

Abstract

Photosynthetic organisms regulate pigment composition and molecular oligomerization of light-harvesting complexes in response to solar light intensities, in order to improve light-harvesting efficiency. Here we report excitation-energy dynamics and relaxation of fucoxanthin chlorophyll a/c-binding protein (FCP) complexes isolated from a diatom Phaeodactylum tricornutum grown under high-light (HL) illumination. Two types of FCP complexes were prepared from this diatom under the HL condition, whereas one FCP complex was isolated from the cells grown under a low-light (LL) condition. The subunit composition and oligomeric states of FCP complexes under the HL condition are different from those under the LL condition. Absorption and fluorescence spectra at 77 K of the FCP complexes also vary between the two conditions, indicating modifications of the pigment composition and arrangement upon the HL illumination. Time-resolved fluorescence curves at 77 K of the FCP complexes under the HL condition showed shorter lifetime components compared with the LL condition. Fluorescence decay-associated spectra at 77 K showed distinct excitation-energy-quenching components and alterations of energy-transfer pathways in the FCP complexes under the HL condition. These findings provide insights into molecular and functional mechanisms of the dynamic regulation of FCPs in this diatom under excess-light conditions.