Arab, D. A. | Search bioRxiv

bioRxiv2020

Evolutionary rates are correlated between Buchnera endosymbionts and mitochondrial genomes of their aphid hosts

The evolution of bacterial endosymbiont genomes is strongly influenced by host-driven selection. Factors affecting host genome evolution will potentially affect endosymbiont genomes in similar ways. One potential outcome is correlations in molecular rates between the genomes of the symbiotic partners. Recently, we presented the first evidence of such a correlation between the mitochondrial genomes of cockroaches and the genome of their endosymbiont (Blattabacterium cuenoti). Here we investigate whether similar patterns are found in additional host-symbiont partners. We use partial genome data from multiple strains of bacterial endosymbionts, B. aphidicola and Sulcia mulleri, and the mitochondrial genomes of their sap-feeding insect hosts. Both endosymbionts show phylogenetic congruence with the mitochondria of their hosts, a result that is expected due to their identical mode of inheritance. We compared root-to-tip distances and branch lengths of phylogenetically independent species pairs. Both analyses show a highly significant correlation of molecular rates between genomes of Buchnera and mitochondrial genomes of their hosts. A similar correlation was detected between Sulcia and their hosts, but was not statistically significant. Our results indicate that evolutionary rate correlations between hosts and long-term symbionts may be a widespread phenomenon.

evolutionary biology↗

bioRxiv2019

Evolutionary rates are correlated between cockroach symbiont and mitochondrial genomes

Bacterial endosymbionts evolve under strong host-driven selection. Factors influencing host evolution might affect symbionts in similar ways, potentially leading to correlations between the molecular evolutionary rates of hosts and symbionts. Although there is evidence of rate correlations between mitochondrial and nuclear genes, similar investigations of hosts and symbionts are lacking. Here we demonstrate a correlation in molecular rates between the genomes of an endosymbiont (Blattabacterium cuenoti) and the mitochondrial genomes of their hosts (cockroaches). We used partial genome data for multiple strains of B. cuenoti to compare phylogenetic relationships and evolutionary rates for 55 cockroach/symbiont pairs. The phylogenies inferred for B. cuenoti and the mitochondrial genomes of their hosts were largely congruent, as expected from their identical maternal and cytoplasmic mode of inheritance. We found a correlation between evolutionary rates of the two genomes, based on comparisons of root-to-tip distances and on comparisons of the branch lengths of phylogenetically independent species pairs. Our results underscore the profound effects that long-term symbiosis can have on the biology of each symbiotic partner.

evolutionary biology↗