Distinctive Genome Reduction Rates Revealed by Genomic Analyses of Two Coxiella-Like Endosymbionts in Ticks.
Bottom Line: Genome reduction is a hallmark of symbiotic genomes, and the rate and patterns of gene loss associated with this process have been investigated in several different symbiotic systems.However, in long-term host-associated coevolving symbiont clades, the genome size differences between strains are normally quite small and hence patterns of large-scale genome reduction can only be inferred from distant relatives.The CRt genome is an extreme example of a symbiont genome caught in the act of genome reduction, and the comparison between CLEAA and CRt indicates that losses of particular genes early on in this process can potentially greatly influence the speed of this process.
Affiliation: Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.Show MeSH
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Mentions: To investigate the dynamics of gene loss and gain in the CRt genome, clustering of orthologous proteins was performed using the proteomes of CRt and 11 other Legionellales and 7 outgroup species. A robust phylogeny created based on the 285 single copy orthologs found in all the species clearly shows the monophyletic relationship between CRt, CLEAA, and C. burnetii, to the exclusion of Rickettsiella (fig. 1A) and confirms that CRt is indeed a species in the genus Coxiella. The two tick symbionts, CRt and CLEAA, group together to form a monophyletic clade, although with CLEAA on a much longer branch than CRt indicating a faster rate of evolution in this symbiont.Fig. 1.—
Affiliation: Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.