Project Details
Projekt
Ca2+ signaling in cyanobacteria multicellularity: Diurnal gating, cell-cell communication and cell differentiation require perception of Ca2+ waves through the Ca2+-sensor protein CSE
Applicant
Professor Dr. Khaled Selim, Ph.D.
Subject Area
Metabolism, Biochemistry and Genetics of Microorganisms
Biochemistry
Biochemistry
Term
since 2022
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 503969687
Cyanobacteria multicellularity involves cell-cell communication via septal junctions 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. While, akinetes, have been evolved as spore-like specialized cells to survive the prolonged periods of unfavorable conditions. However, the signaling machineries that trigger those multicellularity responses are largely unknown. 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 proposal is built on our recent discovery of a new Ca2+-sensor protein, CSE, which is exclusively found in multicellular cyanobacteria. We investigated CSE as a potential link between intracellular Ca2+-signaling and cell-cell communication. We showed that CSE is not only essential for Ca2+ homeostasis, heterocyst differentiation and photosynthesis, but also mediates cell-cell communication via regulating the formation of nanopores — a necessary precursor of septal junctions — as Δcse mutant showed a strong reduction in the number of both nanopores and septal junctions. We therefore intend to delve further into the molecular mechanisms of Ca2+ signaling via CSE, as a driving force for cyanobacterial multicellularity and cell differentiation. We hypothesize the presence of Ca2+ waves that link cell-cell communication and cell differentiation to the metabolic state of the cell, particularly to diurnal rhythm. We identified CSE-interactome, including Ca2+-dependent proteases and cell wall amidase AmiC3, required for nanopores formation. A possible signaling function for CSE may involve regulating the enzymatic activity of its targets via protein-protein interaction to induce differentiation processes or for correct assembly of septal junctions. As a Ca2+-buffer protein, CSE may exert its function via manipulating the free cytoplasmic Ca2+ levels, which might affect processes like gene expression, cell-cell communication, and cell differentiation. To test those hypotheses, we aim to study the signaling role of CSE, on multidimensional levels by combining different biochemical, physiological, microscopic and structural biology approaches to draw a broader picture on its roles in cyanobacteria multicellularity. We therefore aim to 1) decode the molecular details of CSE-interactome to reveal the Ca2+ signaling cascades. 2) decipher the structural and molecular details of Ca2+ waves on diurnal gating and cell-cell communication. 3) Unlock the metabolic details of Ca2+ signaling.
DFG Programme
Priority Programmes
