Abstract
The photoautotrophic lifestyle of cyanobacteria has to cope with the successive diurnal changes. We previously highlighted a unique function of the carbon control protein, SbtB, and its effector molecule c-di-AMP, for nighttime survival through the regulation of glycogen anabolism. However, the extent to which c-di-AMP and SbtB impact the cellular metabolism for day-night survivability remained elusive. To gain a better understanding, we compared the metabolomic and proteomic landscapes of ΔsbtB and the c-di-AMP-free (ΔdacA) mutants of Synechocystis sp. PCC 6803. While our results indicated that the cellular role of SbtB is restricted to carbon/glycogen metabolism, the diurnal lethality of ΔdacA seemed to be a sum of the dysregulation of multiple processes, including photosynthesis and redox regulation. Further, we showed an impact of c-di-AMP on central carbon/nitrogen metabolism, which is linked to NtcA transcription regulation and highlighted by an imbalance of glutamine/glutamate ratio as well as the reduction of arginine pathway metabolites. We further identified the HCO(3) (-) uptake systems, BicA and BCT1, as novel SbtB targets, in agreement with its broader role in regulating carbon homeostasis.