Parallel genome reduction in symbionts descended from closely related free-living bacteria

0483952 - BC 2018 RIV GB eng J - Článek v odborném periodiku
Boscaro, V. - Kolísko, Martin - Felletti, M. - Vannini, C. - Lynn, D. H. - Keeling, P.J.
Parallel genome reduction in symbionts descended from closely related free-living bacteria.
Nature Ecology & Evolution. Roč. 1, č. 8 (2017), s. 1160-1167. ISSN 2397-334X. E-ISSN 2397-334X
Institucionální podpora: RVO:60077344
Klíčová slova: polynucleobacter-necessarius * phylogenetic analysis * maximum-likelihood * evolution * replacement * model * endosymbionts * acceleration * perspectives
Obor OECD: Biochemistry and molecular biology

Endosymbiosis plays an important role in ecology and evolution, but fundamental aspects of the origin of intracellular symbionts remain unclear. The extreme age of many symbiotic relationships, lack of data on free-living ancestors and uniqueness of each event hinder investigations. Here, we describe multiple strains of the bacterium Polynucleobacter that evolved independently and under similar conditions from closely related, free-living ancestors to become obligate endosymbionts of closely related ciliate hosts. As these genomes reduced in parallel from similar starting states, they provide unique glimpses into the mechanisms underlying genome reduction in symbionts. We found that gene loss is contingently lineage-specific, with no evidence for ordered streamlining. However, some genes in otherwise disrupted pathways are retained, possibly reflecting cryptic genetic network complexity. We also measured substitution rates between many endosymbiotic and free-living pairs for hundreds of genes, which showed that genetic drift, and not mutation pressure, is the main non-selective factor driving molecular evolution in endosymbionts.
Trvalý link: http://hdl.handle.net/11104/0279125