Nikkanen L. auteur aut IRD Sanchez A. S. auteur aut IRD Ermakova M. auteur aut IRD Rogner M. auteur aut IRD Cournac Laurent auteur aut IRD Allahverdiyeva Y. auteur aut IRD text journalArticle eng text/pdf reformatted digital access In oxygenic photosynthetic organisms, excluding angiosperms, flavodiiron proteins (FDPs) catalyze light-dependent reduction of O(2)to H2O. This alleviates electron pressure on the photosynthetic apparatus and protects it from photodamage. InSynechocystissp. PCC 6803, four FDP isoforms function as hetero-oligomers of Flv1 and Flv3 and/or Flv2 and Flv4. An alternative electron transport pathway mediated by the NAD(P)H dehydrogenase-like complex (NDH-1) also contributes to redox hemostasis and the photoprotection of photosynthesis. Four NDH-1 types have been characterized in cyanobacteria: NDH-1(1)and NDH-1(2), which function in respiration; and NDH-1(3)and NDH-1(4), which function in CO(2)uptake. All four types are involved in cyclic electron transport. Along with single FDP mutants ( increment flv1and Delta flv3) and the double NDH-1 mutants ( increment d1d2, which is deficient in NDH-1(1,2)and increment d3d4, which is deficient in NDH-1(3,4)), we studied triple mutants lacking one of Flv1 or Flv3, and NDH-1(1,2)or NDH-1(3,4). We show that the presence of either Flv1/3 or NDH-1(1,2), but not NDH-1(3,4), is indispensable for survival during changes in growth conditions from high CO2/moderate light to low CO2/high light. Our results show functional redundancy between FDPs and NDH-1(1,2)under the studied conditions. We suggest that ferredoxin probably functions as a primary electron donor to both Flv1/3 and NDH-1(1,2), allowing their functions to be dynamically coordinated for efficient oxidation of photosystem I and for photoprotection under variable CO(2)and light availability. specialized Flavodiiron proteins Flv NDH-1 photosynthesis Synechocystis sp PCC 6803 cyanobacteria Mehler-like reaction alternative electron transfer photoprotection 076 034 020 103 4 1460-1476 2020 0960-7412 https://www.documentation.ird.fr/hor/fdi:010078179 10.1111/tpj.14812 0960-7412 [F B010078179] https://www.documentation.ird.fr/hor/fdi:010078179 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers20-07/010078179.pdf IRD - Base Horizon / Pleins textes 2020-07-31 2025-02-24 fdi:010078179 fre