Origin and evolution of Cyanobacteria, oxygenic photosynthesis, and plastids: a combined approach based on phylogenomics and molecular techniques – PhyloCyano

The emergence of oxygenic photosynthesis has played a crucial role in early Earth's history. Today, the only organisms that are capable of this process are the Cyanobacteria, as well as photosynthetic eukaryotes via their plastids, which derive from anciently enslaved cyanobacteria. Some cyanobacteria have evolved an important degree of cell differentiation, exceptional among bacteria. This morphological complexity is of extreme importance to palaeoenvironmental research, since it has been used to assign a number of Precambrian microfossils to putative ancient cyanobacterial lineages. However, despite their ecologic and evolutionary importance, the Cyanobacteria remain a poorly studied bacterial phylum. The aim of the proposed project is to explore different aspects of the evolution of Cyanobacteria, oxygenic photosynthesis, and plastids by a double approach: 1) An in silico approach will be assured by the group of the principal investigator, that has a strong expertise in this area. This will be done essentially through the use of phylogenomics methods applied to the current set of complete cyanobacterial genome sequences and those obtained by the second approach. 2) A molecular biology approach, with the cloning and sequencing of a number of target genes from a number of cyanobacterial strains that are poorly represented in current sequence databases and whose genomes are not being sequenced. For this, the project will benefit of a unique opportunity represented by the participation of the Pasteur Collection of Cyanobacteria (PCC), the most important collection of axenic cyanobacteria and a major reference on cyanobacterial features and taxonomy. One of the originalities of the project is that it will establish an important feedback between the group of the principal investigator and the PCC, since data obtained by phylogenomics analyses will be the starting point for gene sequencing, and the novel sequences will be included in further in silico evolutionary analysis. The major outcomes of this project will include: - Clarify the phylogeny of Cyanobacteria. This will be an invaluable tool to set the basis for a much-demanded consensual taxonomy for this phylum and provide a frame to understand the evolution of this important bacterial group. - Study the origin and evolution of photosynthesis. This will allow a better understanding of the timing and mode of emergence of this fundamental metabolism that will be of much interest to biologists, biochemists, and palaeogeologists. - Determine the origin of plastids by identifying their closest cyanobacterial relative. This will be a major finding for Evolutionary studies and Plants research. - Provide a substantial increase in sequence data from a spectrum of cyanobacterial diversity much wider that that currently covered in public sequence databases, that will benefit in the long term to the whole scientific community.