title: Photosystem II supercomplex remodeling serves as an entry mechanism for state transitions in Arabidopsis.
abstract: Within dense plant populations, strong light quality gradients cause unbalanced excitation of the two photosystems resulting in reduced photosynthetic efficiency. Plants redirect such imbalances by structural rearrangements of the photosynthetic apparatus via state transitions and photosystem stoichiometry adjustments. However, less is known about the function of photosystem II (PSII) supercomplexes in this context. Here, we show in Arabidopsis thaliana that PSII supercomplex remodeling precedes and facilitates state transitions. Intriguingly, the remodeling occurs in the short term, paralleling state transitions, but is also present in a state transition-deficient mutant, indicating that PSII supercomplex generation is independently regulated and does not require light-harvesting complex phosphorylation and movement. Instead, PSII supercomplex remodeling involves reversible phosphorylation of PSII core subunits (preferentially of CP43) and requires the luminal PSII subunit Psb27 for general formation and structural stabilization. Arabidopsis knockout mutants lacking Psb27 display highly accelerated state transitions, indicating that release of PSII supercomplexes is required for phosphorylation and subsequent movement of the antenna. Downregulation of PSII supercomplex number by physiological light treatments also results in acceleration of state transitions confirming the genetic analyses. Thus, supercomplex remodeling is a prerequisite and an important kinetic determinant of state transitions.
authors: Lehrstuhl für Pflanzenphysiologie, Friedrich-Schiller-Universität Jena, 07743 Jena, Germany.
authors: Lars
authors: L
authors: Dietzel
authors: Katharina
authors: K
authors: Bräutigam
authors: Sebastian
authors: S
authors: Steiner
authors: Kristin
authors: K
authors: Schüffler
authors: Bernard
authors: B
authors: Lepetit
authors: Bernhard
authors: B
authors: Grimm
authors: Mark Aurel
authors: MA
authors: Schöttler
authors: Thomas
authors: T
authors: Pfannschmidt
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000528:radiation effects / Q000648:ultrastructure; D015536:Down-Regulation; D004579:Electron Transport; D005453:Fluorescence; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000235:genetics / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D010766:Phosphorylation; D010788:Photosynthesis / Q000502:physiology; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000235:genetics / Q000502:physiology / Q000648:ultrastructure; D017384:Sequence Deletion; D020524:Thylakoids / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D029681:Arabidopsis Proteins; D045342:Light-Harvesting Protein Complexes; C576220:PSB27 protein, Arabidopsis; D045332:Photosystem II Protein Complex; C083100:photosystem II, chlorophyll binding protein, CP-43; D002734:Chlorophyll