title: Heterocyst-specific flavodiiron protein Flv3B enables oxic diazotrophic growth of the filamentous cyanobacterium Anabaena sp. PCC 7120.
abstract: Flavodiiron proteins are known to have crucial and specific roles in photoprotection of photosystems I and II in cyanobacteria. The filamentous, heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120 contains, besides the four flavodiiron proteins Flv1A, Flv2, Flv3A, and Flv4 present in vegetative cells, two heterocyst-specific flavodiiron proteins, Flv1B and Flv3B. Here, we demonstrate that Flv3B is responsible for light-induced O2 uptake in heterocysts, and that the absence of the Flv3B protein severely compromises the growth of filaments in oxic, but not in microoxic, conditions. It is further demonstrated that Flv3B-mediated photosynthetic O2 uptake has a distinct role in heterocysts which cannot be substituted by respiratory O2 uptake in the protection of nitrogenase from oxidative damage and, thus, in an efficient provision of nitrogen to filaments. In line with this conclusion, the Δflv3B strain has reduced amounts of nitrogenase NifHDK subunits and shows multiple symptoms of nitrogen deficiency in the filaments. The apparent imbalance of cytosolic redox state in Δflv3B heterocysts also has a pronounced influence on the amounts of different transcripts and proteins. Therefore, an O2-related mechanism for control of gene expression is suggested to take place in heterocysts.
authors.affiliation: Laboratory of Molecular Plant Biology, Department of Biochemistry, University of Turku, FI-20014, Turku, Finland;
authors.forename: Maria
authors.initials: M
authors.lastname: Ermakova
authors.affiliation: Laboratory of Molecular Plant Biology, Department of Biochemistry, University of Turku, FI-20014, Turku, Finland;
authors.forename: Natalia
authors.initials: N
authors.lastname: Battchikova
authors.affiliation: Commissariat à l'Energie Atomique et aux Energies Alternatives, Institut de Biologie Environnementale et de Biotechnologie, Laboratoire de Bioénergétique et Biotechnologie des Bactéries et Microalgues, Cadarache, F-13108 Saint-Paul-lez-Durance, France;Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7265 Biologie Végétale et Microbiologie Environnementales; F-13108 Saint-Paul-lez-Durance, France;Aix Marseille Université, Unité Mixte de Recherche 7265 Biologie Végétale et Microbiologie Environnementales, F-13284 Marseille, France; and.
authors.forename: Pierre
authors.initials: P
authors.lastname: Richaud
authors.affiliation: Laboratory of Molecular Plant Biology, Department of Biochemistry, University of Turku, FI-20014, Turku, Finland;
authors.forename: Hannu
authors.initials: H
authors.lastname: Leino
authors.affiliation: Laboratory of Molecular Plant Biology, Department of Biochemistry, University of Turku, FI-20014, Turku, Finland;
authors.forename: Sergey
authors.initials: S
authors.lastname: Kosourov
authors.affiliation: Laboratory of Molecular Plant Biology, Department of Biochemistry, University of Turku, FI-20014, Turku, Finland;
authors.forename: Janne
authors.initials: J
authors.lastname: Isojärvi
authors.affiliation: Commissariat à l'Energie Atomique et aux Energies Alternatives, Institut de Biologie Environnementale et de Biotechnologie, Laboratoire de Bioénergétique et Biotechnologie des Bactéries et Microalgues, Cadarache, F-13108 Saint-Paul-lez-Durance, France;Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7265 Biologie Végétale et Microbiologie Environnementales; F-13108 Saint-Paul-lez-Durance, France;Aix Marseille Université, Unité Mixte de Recherche 7265 Biologie Végétale et Microbiologie Environnementales, F-13284 Marseille, France; and.
authors.forename: Gilles
authors.initials: G
authors.lastname: Peltier
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas and Universidad de Sevilla, E-41092 Seville, Spain.
authors.forename: Enrique
authors.initials: E
authors.lastname: Flores
authors.affiliation: Commissariat à l'Energie Atomique et aux Energies Alternatives, Institut de Biologie Environnementale et de Biotechnologie, Laboratoire de Bioénergétique et Biotechnologie des Bactéries et Microalgues, Cadarache, F-13108 Saint-Paul-lez-Durance, France;Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7265 Biologie Végétale et Microbiologie Environnementales; F-13108 Saint-Paul-lez-Durance, France;Aix Marseille Université, Unité Mixte de Recherche 7265 Biologie Végétale et Microbiologie Environnementales, F-13284 Marseille, France; and.
authors.forename: Laurent
authors.initials: L
authors.lastname: Cournac
authors.affiliation: Laboratory of Molecular Plant Biology, Department of Biochemistry, University of Turku, FI-20014, Turku, Finland; eva-mari.aro@utu.fi allahve@utu.fi.
authors.forename: Yagut
authors.initials: Y
authors.lastname: Allahverdiyeva
authors.affiliation: Laboratory of Molecular Plant Biology, Department of Biochemistry, University of Turku, FI-20014, Turku, Finland; eva-mari.aro@utu.fi allahve@utu.fi.
authors.forename: Eva-Mari
authors.initials: EM
authors.lastname: Aro
mesh_terms: D017033:Anabaena / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D005420:Flavoproteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D007501:Iron / Q000378:metabolism; D008667:Metalloproteins / Q000235:genetics / Q000378:metabolism*; D009591:Nitrogenase / Q000235:genetics / Q000378:metabolism; D010084:Oxidation-Reduction; D010788:Photosynthesis / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D005420:Flavoproteins; D008667:Metalloproteins; D007501:Iron; D009591:Nitrogenase
keywords: nitrogen fixation; oxygen protection; photosynthesis