Ermakova Maria, Battchikova Natalia, Richaud Pierre, Leino Hannu, Kosourov Sergey, Isojärvi Janne, Peltier Gilles, Flores Enrique, Cournac Laurent, Allahverdiyeva Yagut, Aro Eva-Mari
Laboratory of Molecular Plant Biology, Department of Biochemistry, University of Turku, FI-20014, Turku, Finland;
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.
Proc Natl Acad Sci U S A. 2014 Jul 29;111(30):11205-10. doi: 10.1073/pnas.1407327111. Epub 2014 Jul 7.
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.
已知黄素二铁蛋白在蓝细菌光系统I和II的光保护中发挥关键且特定的作用。丝状、形成异形胞的蓝细菌鱼腥藻属Anabaena sp.菌株PCC 7120，除了营养细胞中存在的四种黄素二铁蛋白Flv1A、Flv2、Flv3A和Flv4外，还含有两种异形胞特异性黄素二铁蛋白Flv1B和Flv3B。在此，我们证明Flv3B负责异形胞中光诱导的氧气摄取，并且Flv3B蛋白的缺失严重损害了丝状藻在有氧条件下的生长，但在微氧条件下则不然。进一步证明，Flv3B介导的光合氧气摄取在异形胞中具有独特作用，在保护固氮酶免受氧化损伤从而有效地为丝状藻提供氮方面，呼吸氧气摄取无法替代该作用。与此结论一致，Δflv3B菌株中固氮酶NifHDK亚基的量减少，并且丝状藻中出现多种氮缺乏症状。Δflv3B异形胞中胞质氧化还原状态的明显失衡也对不同转录本和蛋白质的量产生显著影响。因此，建议在异形胞中存在一种与氧气相关的基因表达调控机制。
