Allahverdiyeva Y. auteur aut IRD Mustila H. auteur aut IRD Ermakova M. auteur aut IRD Bersanini L. auteur aut IRD Richaud P. auteur aut IRD Ajlani G. auteur aut IRD Battchikova N. auteur aut IRD Cournac Laurent auteur aut IRD Aro E. M. auteur aut IRD text journalArticle eng text/pdf born digital access 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. specialized Mehler reaction membrane inlet mass spectrometry photorespiration terminal oxidases 034 020 110 10 4111-4116 2013 0027-8424 https://www.documentation.ird.fr/hor/fdi:010060757 10.1073/pnas.1221194110 0027-8424 [F B010060757] https://www.documentation.ird.fr/hor/fdi:010060757 https://www.documentation.ird.fr/intranet/publi/2013/04/010060757.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2013-05-02 2017-08-23 fdi:010060757 fre