Early Determinants of Heterocyst Differentiation in Multicellular Cyanobacteria

• Prof Dr Rolf Backofen Albert-Ludwigs-Universität Freiburg, Institut für Informatik, Lehrstuhl für Bioinformatik.
• Prof Dr Wolfgang Hess Albert-Ludwigs-Universität Freiburg, Institut für Biologie III.

© SPP2389

Certain multicellular cyanobacteria develop trichomes in which cells are connected by cell-cell adhesion and communicate through gated septal junctions. These cyanobacteria differentiate up to four different cell types, and the trichomes respond to certain stimuli as a whole. Thus, these cyanobacteria fulfil all hallmarks of truly multicellular organisms. Our project targets the earliest steps in the differentiation process of heterocysts, cells specialized for the fixation of N₂ using the enzyme nitrogenase.

Heterocysts are specialized for the fixation of N₂ using the enzyme nitrogenase and are photosynthetically inactive. Heterocysts and the neighbouring photosynthetically active vegetative cells crucially depend on each other and exchange metabolites and signals, which makes the heterocyst-specific N₂ fixation the emergent function that allows these cyanobacteria to survive in nitrogen-poor environments.

The project focuses on understanding the earliest steps in the heterocyst differentiation process in the genetically tractable and well-characterized model Nostoc 7120, on the evolution of the involved genes and mechanisms from non-heterocystous cyanobacteria and on the impact heterocyst differentiation has on environmental bacterial communities.

We apply single cell transcriptomics, identify and characterize early regulators of multicellular decision making, identify tipping points for heterocyst differentiation and extend from analyses in the laboratory to the impact on environmental populations.

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