title: PGR5-PGRL1-Dependent Cyclic Electron Transport Modulates Linear Electron Transport Rate in Arabidopsis thaliana.
abstract: Plants need tight regulation of photosynthetic electron transport for survival and growth under environmental and metabolic conditions. For this purpose, the linear electron transport (LET) pathway is supplemented by a number of alternative electron transfer pathways and valves. In Arabidopsis, cyclic electron transport (CET) around photosystem I (PSI), which recycles electrons from ferrodoxin to plastoquinone, is the most investigated alternative route. However, the interdependence of LET and CET and the relative importance of CET remain unclear, largely due to the difficulties in precise assessment of the contribution of CET in the presence of LET, which dominates electron flow under physiological conditions. We therefore generated Arabidopsis mutants with a minimal water-splitting activity, and thus a low rate of LET, by combining knockout mutations in PsbO1, PsbP2, PsbQ1, PsbQ2, and PsbR loci. The resulting Δ5 mutant is viable, although mature leaves contain only ∼ 20% of wild-type naturally less abundant PsbO2 protein. Δ5 plants compensate for the reduction in LET by increasing the rate of CET, and inducing a strong non-photochemical quenching (NPQ) response during dark-to-light transitions. To identify the molecular origin of such a high-capacity CET, we constructed three sextuple mutants lacking the qE component of NPQ (Δ5 npq4-1), NDH-mediated CET (Δ5 crr4-3), or PGR5-PGRL1-mediated CET (Δ5 pgr5). Their analysis revealed that PGR5-PGRL1-mediated CET plays a major role in ΔpH formation and induction of NPQ in C3 plants. Moreover, while pgr5 dies at the seedling stage under fluctuating light conditions, Δ5 pgr5 plants are able to survive, which underlines the importance of PGR5 in modulating the intersystem electron transfer.
authors.affiliation: Molecular Plant Biology, Department of Biochemistry, University of Turku, 20014 Turku, Finland.
authors.forename: Marjaana
authors.initials: M
authors.lastname: Suorsa
authors.affiliation: Dipartimento di Bioscienze, Università degli studi di Milano, 20133 Milano, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Rossi
authors.affiliation: Plant Molecular Biology (Botany), Department Biology I, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany.
authors.forename: Luca
authors.initials: L
authors.lastname: Tadini
authors.affiliation: Plant Molecular Biology (Botany), Department Biology I, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany.
authors.forename: Mathias
authors.initials: M
authors.lastname: Labs
authors.affiliation: Centro Ricerca e Innovazione, Fondazione Edmund Mach, 38010, San Michele all'Adige, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Colombo
authors.affiliation: Plant Biochemistry, Heinrich-Heine-University Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Jahns
authors.affiliation: Dipartimento di Bioscienze, Università degli studi di Milano, 20133 Milano, Italy.
authors.forename: Martin M
authors.initials: MM
authors.lastname: Kater
authors.affiliation: Plant Molecular Biology (Botany), Department Biology I, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany.
authors.forename: Dario
authors.initials: D
authors.lastname: Leister
authors.affiliation: Laboratoire de Physiologie Cellulaire & Végétale, Unité Mixte de Recherche 5168, Centre National de la Recherche Scientifique, 38054 Grenoble, France.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Finazzi
authors.affiliation: Molecular Plant Biology, Department of Biochemistry, University of Turku, 20014 Turku, Finland.
authors.forename: Eva-Mari
authors.initials: EM
authors.lastname: Aro
authors.affiliation: Dipartimento di Scienze dell'Ambiente e della Vita, Università del Piemonte Orientale, viale Teresa Michel 11, 15121 Alessandria, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Barbato
authors.affiliation: Dipartimento di Bioscienze, Università degli studi di Milano, 20133 Milano, Italy. Electronic address: paolo.pesaresi@unimi.it.
authors.forename: Paolo
authors.initials: P
authors.lastname: Pesaresi
mesh_terms: D017360:Arabidopsis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D004579:Electron Transport; D007700:Kinetics; D008027:Light; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D010788:Photosynthesis / Q000528:radiation effects; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics / Q000378:metabolism*; D045331:Photosystem I Protein Complex / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D008565:Membrane Proteins; C465062:PGR5 protein, Arabidopsis; C527375:PGRL1 protein, Arabidopsis; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex
keywords: Arabidopsis; Cyclic Electron Transport; Linear Electron Transport; Oxygen Evolving Complex; PGR5; Photosynthesis