Project Details
Projekt
Ca2+ signaling in cyanobacteria multicellularity: unravelling the network of the Ca2+ sensor CSE
Applicant
Professor Dr. Khaled Selim
Subject Area
Metabolism, Biochemistry and Genetics of Microorganisms
Biochemistry
Biochemistry
Term
since 2022
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 503969687
The multicellularity in cyanobacteria involves cell-cell communication and cell differentiation into either heterocysts or akinetes, processes that require coordination of individual cells in the filament. Heterocysts have been evolved to spatially separate nitrogen fixation from oxygenic photosynthesis in vegetative cells of the filament, due to the sensitivity of nitrogenase to O2. While, akinetes, have been evolved as spore-like specialized cells to survive the prolonged periods of unfavorable conditions. The differentiation processes have been extensively studied and the underlying molecular mechanisms are relatively well characterized. However, the signaling machinery that triggers those multicellularity responses is only partially elucidated.In multicellular cyanobacteria, a significant role for Ca2+ as a second messenger has been speculated for regulation of heterocyst differentiation, although the Ca2+ signaling cascades and Ca2+ sensors and/or targets remain largely unknown. Our project proposal is built on our recent discovery of a new Ca2+-sensor protein, CSE, which is exclusively found in multicellular cyanobacteria and plays an important role in controlling heterocyst function, assembly of the photosynthetic machinery, and the overall fitness of the filament. We therefore intend to understand the molecular mechanisms of Ca2+ signaling via CSE as a driving force for cyanobacterial multicellularity and differentiation processes.We hypothesize the existence of Ca2+ waves that link heterocyst differentiation and cell-cell communication to the metabolic state of the cell. Likewise, Ca2+ signaling may also influence other multicellular functions such as akinete differentiation. A possible signaling function for CSE may involve a conformational change upon Ca2+ binding to interact with different protein targets for induction of differentiation or for correct assembly of photosynthetic machinery. Also, the CSE protein may exert its function via manipulating the free cytoplasmic Ca2+ ions depending on its cellular abundance, which might affect processes like gene expression, heterocyst development, cell-cell communication, and the protein assembly of the photosynthetic complexes.To test those hypotheses, we aim to study the signaling role of Ca2+, in particular via CSE, on multidimensional levels by combining different biochemical, physiological, microscopic and structural biology approaches to draw a broader picture on their roles in cyanobacteria multicellularity. We therefore aim to 1) determine the physiological significance of Ca2+ waves on gating, cell-cell communication and akinetes differentiation. 2) identify and characterize the CSE-interaction network. 3) elucidate the CSE structure in presence/absence of Ca2+ to determine the Ca2+-binding site(s), which induce(s) CSE conformational changes in CSE. 4) determining the metabolic and transcriptomic impact of high/low intracellular Ca2+-concentrations on central metabolism(optional)
DFG Programme
Priority Programmes
