title: Fingerprinting the macro-organisation of pigment-protein complexes in plant thylakoid membranes in vivo by circular-dichroism spectroscopy.
abstract: Macro-organisation of the protein complexes in plant thylakoid membranes plays important roles in the regulation and fine-tuning of photosynthetic activity. These delicate structures might, however, undergo substantial changes during isolating the thylakoid membranes or during sample preparations, e.g., for electron microscopy. Circular-dichroism (CD) spectroscopy is a non-invasive technique which can thus be used on intact samples. Via excitonic and psi-type CD bands, respectively, it carries information on short-range excitonic pigment-pigment interactions and the macro-organisation (chiral macrodomains) of pigment-protein complexes (psi, polymer or salt-induced). In order to obtain more specific information on the origin of the major psi-type CD bands, at around (+)506, (-)674 and (+)690nm, we fingerprinted detached leaves and isolated thylakoid membranes of wild-type and mutant plants and also tested the effects of different environmental conditions in vivo. We show that (i) the chiral macrodomains disassemble upon mild detergent treatments, but not after crosslinking the protein complexes; (ii) in different wild-type leaves of dicotyledonous and monocotyledonous angiosperms the CD features are quite robust, displaying very similar excitonic and psi-type bands, suggesting similar protein composition and (macro-) organisation of photosystem II (PSII) supercomplexes in the grana; (iii) the main positive psi-type bands depend on light-harvesting protein II contents of the membranes; (iv) the (+)506nm band appears only in the presence of PSII-LHCII supercomplexes and does not depend on the xanthophyll composition of the membranes. Hence, CD spectroscopy can be used to detect different macro-domains in the thylakoid membranes with different outer antenna compositions in vivo.
authors.affiliation: Institute of Plant Biology, Biological Research Centre, Hungarian Academy of Sciences, P.O. Box 521, H-6701 Szeged, Hungary; Laboratory of Biophysics, Wageningen University, P.O. Box 8128, 6700 ET Wageningen, The Netherlands. Electronic address: toth.tunde@brc.mta.hu.
authors.forename: Tünde N
authors.initials: TN
authors.lastname: Tóth
authors.affiliation: Institute of Plant Biology, Biological Research Centre, Hungarian Academy of Sciences, P.O. Box 521, H-6701 Szeged, Hungary. Electronic address: neha15.bhu@gmail.com.
authors.forename: Neha
authors.initials: N
authors.lastname: Rai
authors.affiliation: Department of Plant Anatomy, Institute of Biology, Eötvös Loránd University, H-1117 Budapest, Hungary. Electronic address: katalin.solymosi@ttk.elte.hu.
authors.forename: Katalin
authors.initials: K
authors.lastname: Solymosi
authors.affiliation: Institute of Plant Biology, Biological Research Centre, Hungarian Academy of Sciences, P.O. Box 521, H-6701 Szeged, Hungary. Electronic address: zsiros.otto@brc.mta.hu.
authors.forename: Ottó
authors.initials: O
authors.lastname: Zsiros
authors.affiliation: Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden. Electronic address: wolfgang.schroder@umu.se.
authors.forename: Wolfgang P
authors.initials: WP
authors.lastname: Schröder
authors.affiliation: Institute of Plant Biology, Biological Research Centre, Hungarian Academy of Sciences, P.O. Box 521, H-6701 Szeged, Hungary. Electronic address: garab.gyozo@brc.mta.hu.
authors.forename: Győző
authors.initials: G
authors.lastname: Garab
authors.affiliation: Laboratory of Biophysics, Wageningen University, P.O. Box 8128, 6700 ET Wageningen, The Netherlands. Electronic address: herbert.vanamerongen@wur.nl.
authors.forename: Herbert
authors.initials: H
authors.lastname: van Amerongen
authors.affiliation: Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK. Electronic address: p.horton@sheffield.ac.uk.
authors.forename: Peter
authors.initials: P
authors.lastname: Horton
authors.affiliation: Institute of Plant Biology, Biological Research Centre, Hungarian Academy of Sciences, P.O. Box 521, H-6701 Szeged, Hungary. Electronic address: kovacs.laszlo@brc.mta.hu.
authors.forename: László
authors.initials: L
authors.lastname: Kovács
mesh_terms: D002736:Chloroplasts / Q000648:ultrastructure; D002942:Circular Dichroism; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D018515:Plant Leaves / Q000737:chemistry; D020524:Thylakoids / Q000737:chemistry*; D024341:Xanthophylls / Q000737:chemistry
chemical_list: D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; D024341:Xanthophylls
keywords: Chiral macrodomain; Circular dichroism; Light-harvesting complexes; Photosystem II supercomplexes; Psi-type CD; Thylakoid membrane