The genetic mechanisms for multiseriate filament formation in cyanobacteria

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This proposed project aims to identify the genetic mechanisms that are involved in cyanobacterial morphological complexity and to study their evolutionary history. Cyanobacteria are a monophyletic group of photosynthetic prokaryotes with a long evolutionary trajectory. Contemporary cyanobacteria are successful inhabitants in most environments on Earth and harbor diverse genotypic and phenotypic characteristics. Their morphological diversification comprise unicellular forms dividing by binary fission to multicellular filaments that divide in more than one plane, thus generating multiseriate filaments and true branches. This diversity places cyanobacteria among the most complex prokaryotes. The cyanobacterial common ancestor was most probably unicellular whereas multicellular and true branching species appeared later during evolution. Cyanobacteria have been extensively studied with a focus on the biology of photosynthesis and of nitrogen fixation. Yet the mechanisms involved in multiseriate and true-branching morphology are still unknown, mostly because morphologically complex cyanobacteria have been seldom explored. Here we use multiseriate and true-branching cyanobacteria as model organisms in order to unravel the genetic mechanisms underlying these phenotypes. With the genome sequences at hand, we now wish to proceed with our objective using a functional approach that is aimed to identify the proteins involved in multiseriate and true-branch formation and their relationship with components of the cytoskeleton and cell division machinery. Comparative genomics of the whole phylum is expected to shed light on the emergence of these mechanisms during evolution.