Journal
NEW PHYTOLOGIST
Volume 235, Issue 2, Pages 432-445Publisher
WILEY
DOI: 10.1111/nph.18139
Keywords
Calvin-Benson-Bassham cycle; cyanobacteria; gene regulation; RuBisCO; Synechocystis
Categories
Funding
- German Science Foundation (DFG) [KL3114/2-1]
- German Science Foundation (DFG, graduate school MeInBio) [322977937/GRK2344]
- European Regional Development Fund (EFRE)
- Landtag of Saxony [100361842]
- Helmholtz Association
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Cyanobacteria evolved a CO2 concentrating mechanism to mitigate the ineffective fixation of CO2 by RuBisCO, however, the regulation of these carbon assimilatory systems is still not fully understood. By studying a model cyanobacterium, an essential transcriptional regulator Sll0998 was identified, which controls the activity of RuBisCO, crucial for engineering cyanobacterial cell factories.
Oxygenic photosynthesis evolved in cyanobacteria, primary producers of striking ecological importance. Like plants, cyanobacteria use the Calvin-Benson-Bassham cycle for CO2 fixation, fuelled by ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO). In a competitive reaction this enzyme also fixes O-2 which makes it rather ineffective. To mitigate this problem, cyanobacteria evolved a CO2 concentrating mechanism (CCM) to pool CO2 in the vicinity of RuBisCO. However, the regulation of these carbon (C) assimilatory systems is understood only partially. Using the model Synechocystis sp. PCC 6803 we characterized an essential LysR-type transcriptional regulator encoded by gene sll0998. Transcript profiling of a knockdown mutant revealed diminished expression of several genes involved in C acquisition, including rbcLXS, sbtA and ccmKL encoding RuBisCO and parts of the CCM, respectively. We demonstrate that the Sll0998 protein binds the rbcL promoter and acts as a RuBisCO regulator (RbcR). We propose ATTA(G/A)-N-5-(C/T)TAAT as the binding motif consensus. Our data validate RbcR as a regulator of inorganic C assimilation and define the regulon controlled by it. Biological CO2 fixation can sustain efforts to reduce its atmospheric concentrations and is fundamental for the light-driven production of chemicals directly from CO2. Information about the involved regulatory and physiological processes is crucial to engineer cyanobacterial cell factories.
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