Calcium (Ca2+) is one of the most important second messengers, and is known to regulate metabolic and/or differentiation processes in eukaryotic cells. Much less is known about the role of Ca2+ in prokaryotes and especially cyanobacteria and how they sense Ca2+. Therefore, we aim to uncover the role of Ca2+ signaling in the multicellular lifestyle of the diazotrophic cyanobacteria. Recently within the frame of an international cooperation, we identified a novel Ca2+-Sensor protein (CSE protein). CSE protein is important for filament integrity, cell differentiation into heterocyst cells, N2 fixation and the regulation of photosynthesis in diazotrophic multicellular cyanobacteria.
In addition, we are currently investigating the signaling roles of the cyclic di-nucleotides c-di-AMP and c-di-GMP in unicellular cyanobacteria. We identified several of novel c-di-AMP and c-di-GMP receptors as well as RNA-riboswitches, with putative roles in Carbon/Nitrogen metabolisms and photosynthetic day/night and/or phototaxis motility lifestyles. We are currently exploring the regulatory functions of those new c-di-AMP and c-di-GMP receptors.