Uso de filogenia molecular, genômica comparativa e redes complexas para resolver relações evolutivas entre FtsHs do filo Cyanobacteria

Abstract

Introduction. Species of the Phylum Cyanobacteria possessing two or more copies of genes encoding FtsH (filamentation temperature sensitive). These proteins are involved in photosynthetic metabolism and previous studies showed that they are phylogenetically and functionally related to plastidial FtsHs. Despite its importance, the evolutionary history of cyanobacteria FtsHs remain to be elucidated. General objective. Understanding the evolutionary relationships between FtsHs encoded in the genomes of cyanobacteria. Methods. Phylogenetic relationships between FtsHs encoded in 66 completely sequenced cyanobacterial genomes available at NCBI (National Center for Biotechnology Information) they were investigated using molecular phylogeny, comparative genomics and construction of complex networks from the identity matrix proteins, a method recently developed to make phylogenetic inferences. Results. The number of gene copies encoding the cyanobacterial FtsH genomes examined varies from two to nine copies. The results presented here indicate that there are at least seven paralogs of FtsH in cyanobacteria. The paralogous FtsHcb1A, FtsHcb1B and FtsHcb1C derive from an ancestral FtsH originating from a horizontal transfer event (THG) genes in the ancestor of cyanobacteria, in contrast to the paralogous FtsHcb2A, FtsHcb2B, FtsHcb3 and FtsHcb4, that derive from gene duplication events of native ancestral FtsH of cyanobacteria. The genes encoding FtsHcb2A, FtsHcb2B and FtsHcb3 are widely distributed in the cyanobacterial genomes, however, FtsHcb3 is the only paralogue that is present in all the genomes analyzed. It was observed a co-occurrence of genes encoding FtsHcb1C, FtsHcb2A, FtsHcb3 and FtsHcb4, this may indicate some sort of functional interaction between these paralogous. The FtsHcb3 is the most conserved paralogue, in contrast to FtsHcb4. The paralogous of FtsHcb4 encoded in Prochlorococcus marinus genomes have an atypical zinc-binding motif, NEVGR, it was not described yet for FtsH, suggesting a functional divergence of the paralogue in this species. Conclusion. The results presented here show that both THG and gene duplication events have shaped the diversity of FtsHs in Filo Cyanobacteria. Additionally, these results show that complex networks obtained from the identity matrix genes and proteins are useful tools in defining the homology relationships between genes or proteins.