title: Disturbed excitation energy transfer in Arabidopsis thaliana mutants  lacking minor antenna complexes of photosystem II.
abstract: Minor light-harvesting complexes (Lhcs) CP24, CP26 and CP29 occupy a position in photosystem II (PSII c' plants between the major light-harvesting complexes LHCII and the PSII core subunits. Lack of minor Lhcs in vivo causes impairment of PSII organization, and negatively affects electron transport rates anc photoprotection capacity. Here we used picosecond-fluorescence spectroscopy to study excitation-energy transfer (EET) in thylakoid membranes isolated from Arabidopsis thaliana wild-type plants and knockout lines depleted of either two (koCP26/24 and koCP29/24) or all minor Lhcs (NoM). In the absence of all minor Lhcs. the functional connection ofLHCII to the PSII cores appears to be seriously impaired whereas the "disconnected" LHCII is substantially quenched. For both double knock-out mutants, excitation trapping in PSII is faster than in NoM thylakoids but slower than in WT thylakoids. In NoM thylakoids, the loss of all minor Lhcs is accompanied by an over-accumulation ofLHCII, suggesting a compensating response to the reduced trapping efficiency in limiting light, which leads to a photosynthetic phenotype resembling that of low-light-acclimated plants. Finally. fluorescence kinetics and biochemical results show that the missing minor complexes are not replaced by other Lhcs, implying that they are unique among the antenna subunits and crucial for the functioning and macroorganization of PSII.
authors.affiliation: Dipartimento di Biotecnologie, Università di Verona, 37134 Verona, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Dall'Osto
authors.affiliation: Laboratory of Biophysics, Wageningen University, 6703 HA Wageningen, The Netherlands.
authors.forename: Caner
authors.initials: C
authors.lastname: Ünlü
authors.affiliation: Dipartimento di Biotecnologie, Università di Verona, 37134 Verona, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Cazzaniga
authors.affiliation: Laboratory of Biophysics, Wageningen University, 6703 HA Wageningen, The Netherlands; MicroSpectroscopy Centre, Wageningen University, 6703 HA Wageningen, The Netherlands. Electronic address: herbert.vanamerongen@wur.nl.
authors.forename: Herbert
authors.initials: H
authors.lastname: van Amerongen
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002734:Chlorophyll / Q000737:chemistry / Q000378:metabolism; D061146:Chlorophyll Binding Proteins / Q000235:genetics* / Q000378:metabolism; D060365:Chloroplast Proteins / Q000235:genetics* / Q000378:metabolism; D004735:Energy Transfer; D005453:Fluorescence; D015151:Immunoblotting; D009154:Mutation; D010084:Oxidation-Reduction; D045332:Photosystem II Protein Complex / Q000235:genetics* / Q000378:metabolism; D012261:Ribonucleoproteins / Q000235:genetics* / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D020524:Thylakoids / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
chemical_list: D029681:Arabidopsis Proteins; D061146:Chlorophyll Binding Proteins; D060365:Chloroplast Proteins; C490432:LHCB5 protein, Arabidopsis; C529795:Lhcb6 protein, Arabidopsis; D045332:Photosystem II Protein Complex; C529074:RBP29 protein, Arabidopsis; D012261:Ribonucleoproteins; D002734:Chlorophyll