A1 Refereed original research article in a scientific journal
Flavodiiron proteins Flv1 and Flv3 enable cyanobacterial growth and photosynthesis under fluctuating light
Authors: Allahverdiyeva Y, Mustila H, Ermakova M, Bersanini L, Richaud P, Ajlani G, Battchikova N, Cournac L, Aro EM
Publisher: NATL ACAD SCIENCES
Publication year: 2013
Journal: Proceedings of the National Academy of Sciences of the United States of America
Journal name in source: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Journal acronym: P NATL ACAD SCI USA
Number in series: 10
Volume: 110
Issue: 10
First page : 4111
Last page: 4116
Number of pages: 6
ISSN: 1091-6490
DOI: https://doi.org/10.1073/pnas.1221194110
Abstract
Cyanobacterial flavodiiron proteins (FDPs; A-type flavoprotein, Flv) comprise, besides the beta-lactamase-like and flavodoxin domains typical for all FDPs, an extra NAD(P)H:flavin oxidoreductase module and thus differ from FDPs in other Bacteria and Archaea. Synechocystis sp. PCC 6803 has four genes encoding the FDPs. Flv1 and Flv3 function as an NAD(P) H: oxygen oxidoreductase, donating electrons directly to O-2 without production of reactive oxygen species. Here we show that the Flv1 and Flv3 proteins are crucial for cyanobacteria under fluctuating light, a typical light condition in aquatic environments. Under constant-light conditions, regardless of light intensity, the Flv1 and Flv3 proteins are dispensable. In contrast, under fluctuating light conditions, the growth and photosynthesis of the Delta flv1(A) and/or Delta flv3(A) mutants of Synechocystis sp. PCC 6803 and Anabaena sp. PCC 7120 become arrested, resulting in cell death in the most severe cases. This reaction is mainly caused by malfunction of photosystem I and oxidative damage induced by reactive oxygen species generated during abrupt short-term increases in light intensity. Unlike higher plants that lack the FDPs and use the Proton Gradient Regulation 5 to safeguard photosystem I, the cyanobacterial homolog of Proton Gradient Regulation 5 is shown not to be crucial for growth under fluctuating light. Instead, the unique Flv1/Flv3 heterodimer maintains the redox balance of the electron transfer chain in cyanobacteria and provides protection for photosystem I under fluctuating growth light. Evolution of unique cyanobacterial FDPs is discussed as a prerequisite for the development of oxygenic photosynthesis.
Cyanobacterial flavodiiron proteins (FDPs; A-type flavoprotein, Flv) comprise, besides the beta-lactamase-like and flavodoxin domains typical for all FDPs, an extra NAD(P)H:flavin oxidoreductase module and thus differ from FDPs in other Bacteria and Archaea. Synechocystis sp. PCC 6803 has four genes encoding the FDPs. Flv1 and Flv3 function as an NAD(P) H: oxygen oxidoreductase, donating electrons directly to O-2 without production of reactive oxygen species. Here we show that the Flv1 and Flv3 proteins are crucial for cyanobacteria under fluctuating light, a typical light condition in aquatic environments. Under constant-light conditions, regardless of light intensity, the Flv1 and Flv3 proteins are dispensable. In contrast, under fluctuating light conditions, the growth and photosynthesis of the Delta flv1(A) and/or Delta flv3(A) mutants of Synechocystis sp. PCC 6803 and Anabaena sp. PCC 7120 become arrested, resulting in cell death in the most severe cases. This reaction is mainly caused by malfunction of photosystem I and oxidative damage induced by reactive oxygen species generated during abrupt short-term increases in light intensity. Unlike higher plants that lack the FDPs and use the Proton Gradient Regulation 5 to safeguard photosystem I, the cyanobacterial homolog of Proton Gradient Regulation 5 is shown not to be crucial for growth under fluctuating light. Instead, the unique Flv1/Flv3 heterodimer maintains the redox balance of the electron transfer chain in cyanobacteria and provides protection for photosystem I under fluctuating growth light. Evolution of unique cyanobacterial FDPs is discussed as a prerequisite for the development of oxygenic photosynthesis.
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