title: Regulation of photosystem I light harvesting by zeaxanthin.
abstract: In oxygenic photosynthetic eukaryotes, the hydroxylated carotenoid zeaxanthin is produced from preexisting violaxanthin upon exposure to excess light conditions. Zeaxanthin binding to components of the photosystem II (PSII) antenna system has been investigated thoroughly and shown to help in the dissipation of excess chlorophyll-excited states and scavenging of oxygen radicals. However, the functional consequences of the accumulation of the light-harvesting complex I (LHCI) proteins in the photosystem I (PSI) antenna have remained unclarified so far. In this work we investigated the effect of zeaxanthin binding on photoprotection of PSI-LHCI by comparing preparations isolated from wild-type Arabidopsis thaliana (i.e., with violaxanthin) and those isolated from the A. thaliana nonphotochemical quenching 2 mutant, in which violaxanthin is replaced by zeaxanthin. Time-resolved fluorescence measurements showed that zeaxanthin binding leads to a previously unrecognized quenching effect on PSI-LHCI fluorescence. The efficiency of energy transfer from the LHCI moiety of the complex to the PSI reaction center was down-regulated, and an enhanced PSI resistance to photoinhibition was observed both in vitro and in vivo. Thus, zeaxanthin was shown to be effective in inducing dissipative states in PSI, similar to its well-known effect on PSII. We propose that, upon acclimation to high light, PSI-LHCI changes its light-harvesting efficiency by a zeaxanthin-dependent quenching of the absorbed excitation energy, whereas in PSII the stoichiometry of LHC antenna proteins per reaction center is reduced directly.
authors.affiliation: Department of Biotechnology, University of Verona, I-37134 Verona, Italy;
authors.forename: Matteo
authors.initials: M
authors.lastname: Ballottari
authors.affiliation: Center for Nanoscience and Technology, Italian Institute of Technology, Polytechnic University of Milan, 20133 Milan, Italy;Institute for Photonics and Nanotechnology, National Research Council, Department of Physics, Polytechnic University of Milan, 20133 Milan, Italy;
authors.forename: Marcelo J P
authors.initials: MJ
authors.lastname: Alcocer
authors.affiliation: Center for Nanoscience and Technology, Italian Institute of Technology, Polytechnic University of Milan, 20133 Milan, Italy;Institute for Photonics and Nanotechnology, National Research Council, Department of Physics, Polytechnic University of Milan, 20133 Milan, Italy;
authors.forename: Cosimo
authors.initials: C
authors.lastname: D'Andrea
authors.affiliation: Institute for Photonics and Nanotechnology, National Research Council, Department of Physics, Polytechnic University of Milan, 20133 Milan, Italy;
authors.forename: Daniele
authors.initials: D
authors.lastname: Viola
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720;Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Korea; andDepartment of Chemistry, University of California, Berkeley, CA 94720.
authors.forename: Tae Kyu
authors.initials: TK
authors.lastname: Ahn
authors.affiliation: Center for Nanoscience and Technology, Italian Institute of Technology, Polytechnic University of Milan, 20133 Milan, Italy;
authors.forename: Annamaria
authors.initials: A
authors.lastname: Petrozza
authors.affiliation: Center for Nanoscience and Technology, Italian Institute of Technology, Polytechnic University of Milan, 20133 Milan, Italy;Institute for Photonics and Nanotechnology, National Research Council, Department of Physics, Polytechnic University of Milan, 20133 Milan, Italy;
authors.forename: Dario
authors.initials: D
authors.lastname: Polli
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720;Department of Chemistry, University of California, Berkeley, CA 94720.
authors.forename: Graham R
authors.initials: GR
authors.lastname: Fleming
authors.affiliation: Institute for Photonics and Nanotechnology, National Research Council, Department of Physics, Polytechnic University of Milan, 20133 Milan, Italy;
authors.forename: Giulio
authors.initials: G
authors.lastname: Cerullo
authors.affiliation: Department of Biotechnology, University of Verona, I-37134 Verona, Italy; roberto.bassi@univr.it.
authors.forename: Roberto
authors.initials: R
authors.lastname: Bassi
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D005453:Fluorescence; D007700:Kinetics; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000235:genetics / Q000378:metabolism*; D008163:Luminescent Measurements / Q000295:instrumentation / Q000379:methods; D009154:Mutation; D010788:Photosynthesis / Q000528:radiation effects; D045331:Photosystem I Protein Complex / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D013997:Time Factors; D024341:Xanthophylls / Q000378:metabolism*; D065146:Zeaxanthins
chemical_list: D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; D024341:Xanthophylls; D065146:Zeaxanthins; D002734:Chlorophyll
keywords: photobleaching; photosynthesis; violaxanthin de-epoxidase; xanthophylls