CyanoClust: Protein Cluster Database for Comparative genomics of Cyanobacteria and Plastids

Chloroplasts are the sites of photosynthesis within the cell of land plants and algae. In non-photosynthetic tissues of plants, they are called plastids. Various lines of evidence, such as similarity of photosynthetic machineries and photosynthetic metabolic pathways as well as fossil records, suggested that the cyanobacteria are related to the origin of chloroplasts [1]. Now, cyanobacteria exhibit ecologically and morphologically adapted to wide ecological spectrum from Antarctica to the desert and even in some hot springs. Although their evolutional history is complicated, the clade structure and the lineage of cyanobacteria have been revealed by careful molecular phylogenetic analyses. These findings also encourage the efforts to deciphering the endosymbiosis process of the chloroplasts. Nevertheless, instead of the intuitive idea that the plastids and the host plant cells were co-evolved, actual evolutional relationship between the host cells and the plastids still remains complex as seen in the secondary symbiosis [2]. To study the evolution of plastids, there are some useful platforms of comparative genomic analyses such as ChloroplastDB [4]. But resources for comparative genomics of plastids and cyanobacteria are limited. Here we developed CyanoClust database web server for providing reliable orthologs over many cyanobacteria and plastids, or just various cyanobacteria, which is also used as a platform of comparative genome analysis. For the comparison of orthologs among loosely related organisms, the Gclust software, which was developed in our laboratory [3] was used for the construction of the database.