title: Live-cell imaging of photosystem II antenna dissociation during state transitions.
abstract: Plants and green algae maintain efficient photosynthesis under changing light environments by adjusting their light-harvesting capacity. It has been suggested that energy redistribution is brought about by shuttling the light-harvesting antenna complex II (LHCII) between photosystem II (PSII) and photosystem I (PSI) (state transitions), but such molecular remodeling has never been demonstrated in vivo. Here, using chlorophyll fluorescence lifetime imaging microscopy, we visualized phospho-LHCII dissociation from PSII in live cells of the green alga Chlamydomonas reinhardtii. Induction of energy redistribution in wild-type cells led to an increase in, and spreading of, a 250-ps lifetime chlorophyll fluorescence component, which was not observed in the stt7 mutant incapable of state transitions. The 250-ps component was also the dominant component in a mutant containing the light-harvesting antenna complexes but no photosystems. The appearance of the 250-ps component was accompanied by activation of LHCII phosphorylation, supporting the visualization of phospho-LHCII dissociation. Possible implications of the unbound phospho-LHCII on energy dissipation are discussed.
authors.affiliation: Institute of Low Temperature Science, Hokkaido University, N19 W8, Sapporo, Hokkaido 060-0819, Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Iwai
authors.forename: Makio
authors.initials: M
authors.lastname: Yokono
authors.forename: Noriko
authors.initials: N
authors.lastname: Inada
authors.forename: Jun
authors.initials: J
authors.lastname: Minagawa
mesh_terms: D020418:Algal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism; D017125:Genes, Protozoan; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry; D009154:Mutation; D045331:Photosystem I Protein Complex / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D020418:Algal Proteins; D045342:Light-Harvesting Protein Complexes; D046912:Multiprotein Complexes; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D015800:Protozoan Proteins; D002734:Chlorophyll