title: The light-harvesting chlorophyll a/b binding proteins Lhcb1 and Lhcb2 play complementary roles during state transitions in Arabidopsis.
abstract: Photosynthetic light harvesting in plants is regulated by phosphorylation-driven state transitions: functional redistributions of the major trimeric light-harvesting complex II (LHCII) to balance the relative excitation of photosystem I and photosystem II. State transitions are driven by reversible LHCII phosphorylation by the STN7 kinase and PPH1/TAP38 phosphatase. LHCII trimers are composed of Lhcb1, Lhcb2, and Lhcb3 proteins in various trimeric configurations. Here, we show that despite their nearly identical amino acid composition, the functional roles of Lhcb1 and Lhcb2 are different but complementary. Arabidopsis thaliana plants lacking only Lhcb2 contain thylakoid protein complexes similar to wild-type plants, where Lhcb2 has been replaced by Lhcb1. However, these do not perform state transitions, so phosphorylation of Lhcb2 seems to be a critical step. In contrast, plants lacking Lhcb1 had a more profound antenna remodeling due to a decrease in the amount of LHCII trimers influencing thylakoid membrane structure and, more indirectly, state transitions. Although state transitions are also found in green algae, the detailed architecture of the extant seed plant light-harvesting antenna can now be dated back to a time after the divergence of the bryophyte and spermatophyte lineages, but before the split of the angiosperm and gymnosperm lineages more than 300 million years ago.
authors.affiliation: Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, 901 87 Umeå, Sweden.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Pietrzykowska
authors.affiliation: Molecular Plant Biology, Department of Biochemistry, University of Turku, 20520 Turku, Finland.
authors.forename: Marjaana
authors.initials: M
authors.lastname: Suorsa
authors.affiliation: Electron Microscopy Group, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747AG Groningen, The Netherlands.
authors.forename: Dmitry A
authors.initials: DA
authors.lastname: Semchonok
authors.affiliation: Molecular Plant Biology, Department of Biochemistry, University of Turku, 20520 Turku, Finland.
authors.forename: Mikko
authors.initials: M
authors.lastname: Tikkanen
authors.affiliation: Electron Microscopy Group, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747AG Groningen, The Netherlands.
authors.forename: Egbert J
authors.initials: EJ
authors.lastname: Boekema
authors.affiliation: Molecular Plant Biology, Department of Biochemistry, University of Turku, 20520 Turku, Finland.
authors.forename: Eva-Mari
authors.initials: EM
authors.lastname: Aro
authors.affiliation: Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, 901 87 Umeå, Sweden stefan.jansson@umu.se.
authors.forename: Stefan
authors.identifier: http://orcid.org/0000-0002-7906-6891
authors.initials: S
authors.lastname: Jansson
mesh_terms: D017360:Arabidopsis / Q000378:metabolism* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism*; D000077194:Chlorophyll A; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism*; D035683:MicroRNAs / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D010641:Phenotype; D010766:Phosphorylation; D010788:Photosynthesis; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D011485:Protein Binding; D055503:Protein Multimerization; D020524:Thylakoids / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D029681:Arabidopsis Proteins; C423618:CAB2 protein, Arabidopsis; C000602509:Lhcb2 protein, Arabidopsis; D045342:Light-Harvesting Protein Complexes; D035683:MicroRNAs; D010455:Peptides; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D002734:Chlorophyll; C037184:chlorophyll b; D000077194:Chlorophyll A