Heterocyst-specific flavodiiron protein Flv3B enables oxic diazotrophic growth of the filamentous cyanobacterium Anabaena sp. PCC 7120

Maria Ermakova, Natalia Battchikova, Pierre Richaud, Hannu Leino, Sergey Kosourov, Janne Isojar̈vi, Gilles Peltier, Enrique Flores, Laurent Cournac, Yagut Allahverdiyeva*, Eva Mari Aro

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

46 Citations (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)11205-11210
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume111
Issue number30
DOIs
Publication statusPublished - 2014
Externally publishedYes

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