title: Changes in antenna sizes of photosystems during state transitions in granal and stroma-exposed thylakoid membrane of intact chloroplasts in Arabidopsis mesophyll protoplasts.
abstract: In chloroplasts of plants and algae, state transition is an important regulatory mechanism to maintain the excitation balance between PSI and PSII in the thylakoid membrane. Light-harvesting complex II (LHCII) plays a key role as the regulated energy distributor between PSI and PSII. It is widely accepted that LHCII, which is bound to PSII localized mainly in the granal thylakoid, migrates to bind with PSI localized mainly in the stroma-exposed thylakoid under preferential excitation of PSII. The phenomena have been extensively characterized by many methods. However, the exchange of LHCII between PSII and PSI has not been directly observed in vivo at physiological temperatures. Herein we applied fluorescence spectromicroscopy to Arabidopsis mesophyll protoplasts in order to observe in vivo changes in fluorescence spectra of granal and stromal thylakoid regions during the state transition. The microscopic fluorescence spectra obtained from a few sections with different depths were decomposed into PSI and PSII spectra and self-absorption effects were removed. We were able to determine amplitude changes of PSI and PSII in fluorescence spectra solely due to state transition. Subdomain analysis of granal and stromal thylakoid regions clarified variant behaviors in the different regions.
authors.affiliation: Department of Energy Science, Sungkyunkwan University, Suwon, 440-746 Korea.
authors.forename: Eunchul
authors.initials: E
authors.lastname: Kim
authors.affiliation: Department of Energy Science, Sungkyunkwan University, Suwon, 440-746 Korea kumazaki@kuchem.kyoto-u.ac.jp taeahn@skku.edu.
authors.forename: Tae Kyu
authors.initials: TK
authors.lastname: Ahn
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto, 606-8502 Japan kumazaki@kuchem.kyoto-u.ac.jp taeahn@skku.edu.
authors.forename: Shigeichi
authors.initials: S
authors.lastname: Kumazaki
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism*; D058503:Mesophyll Cells / Q000378:metabolism*; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D011523:Protoplasts / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D020524:Thylakoids / Q000378:metabolism*
chemical_list: D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex
keywords: Chloroplast; Fluorescence spectromicroscopy; Light-harvesting complex; Photosystem; State transition; Thylakoid membrane