title: Live-cell visualization of excitation energy dynamics in chloroplast thylakoid structures.
abstract: The intricate molecular processes underlying photosynthesis have long been studied using various analytic approaches. However, the three-dimensional (3D) dynamics of such photosynthetic processes remain unexplored due to technological limitations related to investigating intraorganellar mechanisms in vivo. By developing a system for high-speed 3D laser scanning confocal microscopy combined with high-sensitivity multiple-channel detection, we visualized excitation energy dynamics in thylakoid structures within chloroplasts of live Physcomitrella patens cells. Two distinct thylakoid structures in the chloroplast, namely the grana and stroma lamellae, were visualized three-dimensionally in live cells. The simultaneous detection of the shorter (than ~670 nm) and longer (than ~680 nm) wavelength regions of chlorophyll (Chl) fluorescence reveals different spatial characteristics-irregular and vertical structures, respectively. Spectroscopic analyses showed that the shorter and longer wavelength regions of Chl fluorescence are affected more by free light-harvesting antenna proteins and photosystem II supercomplexes, respectively. The high-speed 3D time-lapse imaging of the shorter and longer wavelength regions also reveals different structural dynamics-rapid and slow movements within 1.5 seconds, respectively. Such structural dynamics of the two wavelength regions of Chl fluorescence would indicate excitation energy dynamics between light-harvesting antenna proteins and photosystems, reflecting the energetically active nature of photosynthetic proteins in thylakoid membranes.
authors.affiliation: Live Cell Super-Resolution Imaging Research Team, Extreme Photonics Research Group, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.|PRESTO, Japan Science and Technology Agency (JST), Honcho, Kawaguchi, Saitama 332-0012 Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Iwai
authors.affiliation: Institute of Low Temperature Science, Hokkaido University, Sapporo, Hokkaido 060-0819 Japan.
authors.forename: Makio
authors.initials: M
authors.lastname: Yokono
authors.affiliation: Live Cell Super-Resolution Imaging Research Team, Extreme Photonics Research Group, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kurokawa
authors.affiliation: Live Cell Super-Resolution Imaging Research Team, Extreme Photonics Research Group, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Ichihara
authors.affiliation: Live Cell Super-Resolution Imaging Research Team, Extreme Photonics Research Group, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.|Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Nakano
mesh_terms: D019068:Bryopsida / Q000166:cytology* / Q000378:metabolism*; D002470:Cell Survival; D002734:Chlorophyll / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D021621:Imaging, Three-Dimensional; D018613:Microscopy, Confocal / Q000379:methods*; D059828:Plant Cells / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics; D020524:Thylakoids / Q000378:metabolism*; D059008:Time-Lapse Imaging
chemical_list: D002734:Chlorophyll; D049452:Green Fluorescent Proteins