Flavodiiron proteins 1-to-4 function in versatile combinations in O2 photoreduction in cyanobacteria

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Abstract

Flavodiiron proteins (FDPs) constitute a group of modular enzymes widespread in all life Domains. Synechocystis sp. PCC 6803 has four FDPs (Flv1-4), which are essential for the photoprotection of photosynthesis. A direct comparison of light-induced O₂reduction (Mehler-like reaction) under high (3% CO₂, HC) and low (air level CO₂, LC) inorganic carbon conditions demonstrated that the Flv1/Flv3 heterodimer is solely responsible for an efficient steady-state O₂ photoreduction under HC, with flv2 and flv4 expression strongly down-regulated. Conversely, under LC conditions, Flv1/Flv3 acts only as a transient electron sink, due to the competing withdrawal of electrons by the highly induced NDH-1 complex. Further, in vivo evidence is provided indicating that Flv2/Flv4 contributes to the Mehler-like reaction when naturally expressed under LC conditions, or, when artificially overexpressed under HC. The O₂photoreduction driven by Flv2/Flv4 occurs down-stream of PSI in a coordinated manner with Flv1/Flv3 and supports slow and steady-state O₂ photoreduction.

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All data generated or analysed during this study are included in the manuscript and supporting files.

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Anita Isabel Santana Sanchez

Department of Biochemistry, University of Turku, Turku, Finland

Competing interests
The authors declare that no competing interests exist.
Daniel Solymosi

Department of Biochemistry, University of Turku, Turku, Finland

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The authors declare that no competing interests exist.
Henna Mustila

Microbial Chemistry, University of Uppsala, Uppsala, Sweden

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The authors declare that no competing interests exist.
Luca Bersanini

Department of Physics and Astronomy, Vrije Universiteit Amsterdam, Amsterdam, Netherlands

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The authors declare that no competing interests exist.
Eva-Mari Aro

Department of Biochemistry, University of Turku, Turku, Finland

For correspondence
evaaro@utu.fi

Competing interests
The authors declare that no competing interests exist.
Yagut Allahverdiyeva-Rinne

Department of Biochemistry, University of Turku, Turku, Finland

For correspondence
allahve@utu.fi

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-9262-1757

Funding

Suomen Akatemia (315119)

Yagut Allahverdiyeva-Rinne

NordForsk (82845)

Eva-Mari Aro
Yagut Allahverdiyeva-Rinne

Koneen Säätiö (7fa491)

Yagut Allahverdiyeva-Rinne

Suomen Akatemia (307335)

Eva-Mari Aro

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

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This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.