title: Regulation of excitation energy transfer in diatom PSII dimer: How does it change the destination of excitation energy?
abstract: Energy transfer dynamics in dimeric photosystem II (PSII) complexes isolated from four diatoms, Chaetoceros gracilis, Cyclotella meneghiniana, Thalassiosira pseudonana, and Phaeodactylum tricornutum, are examined. Time-resolved fluorescence measurements were conducted in the range of 0-80ns. Delayed fluorescence spectra showed a clear difference between PSII monomer and PSII dimer isolated from the four diatoms. The difference can be interpreted as reflecting suppressed energy transfer between PSII monomers in the PSII dimer for efficient energy trapping at the reaction center. The observation was especially prominent in C. gracilis and T. pseudonana. The pathways seem to be suppressed under a low pH condition in isolated PSII complexes from C. gracilis, and excitation energy may be quenched with fucoxanthin chlorophyll a/c-binding protein (FCP) that was closely associated with PSII in C. gracilis. The energy transfer between PSII monomers in the PSII dimer may play a role in excitation energy regulation in diatoms.
authors.affiliation: Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819, Japan. Electronic address: filia@mac.com.
authors.forename: Makio
authors.initials: M
authors.lastname: Yokono
authors.affiliation: Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Nagao
authors.affiliation: Department of Biology, Faculty of Science, Tokyo University of Science, Kagurazaka 1-3, Shinjuku-ku, Tokyo 162-8601, Japan; PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Tomo
authors.affiliation: Molecular Photoscience Research Center, Kobe University, Kobe 657-8501, Japan; JST, CREST, Kobe 657-8501, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Akimoto
keywords: Diatom; Energy transfer; PSII dimer; Quench; Time-resolved fluorescence