title: Happens in the best of subfamilies: establishment and repeated replacements of co-obligate secondary endosymbionts within Lachninae aphids.
abstract: Virtually all aphids maintain an obligate mutualistic symbiosis with bacteria from the Buchnera genus, which produce essential nutrients for their aphid hosts. Most aphids from the Lachninae subfamily have been consistently found to house additional endosymbionts, mainly Serratia symbiotica. This apparent dependence on secondary endosymbionts was proposed to have been triggered by the loss of the riboflavin biosynthetic capability by Buchnera in the Lachninae last common ancestor. However, an integral large-scale analysis of secondary endosymbionts in the Lachninae is still missing, hampering the interpretation of the evolutionary and genomic analyses of these endosymbionts. Here, we analysed the endosymbionts of selected representatives from seven different Lachninae genera and nineteen species, spanning four tribes, both by FISH (exploring the symbionts' morphology and tissue tropism) and 16S rRNA gene sequencing. We demonstrate that all analysed aphids possess dual symbiotic systems, and while most harbour S. symbiotica, some have undergone symbiont replacement by other phylogenetically-distinct bacterial taxa. We found that these secondary associates display contrasting cell shapes and tissue tropism, and some appear to be lineage-specific. We propose a scenario for symbiont establishment in the Lachninae, followed by changes in the symbiont's tissue tropism and symbiont replacement events, thereby highlighting the extraordinary versatility of host-symbiont interactions.
authors.affiliation: Institut Cavanilles de Biodiversitat i Biologia Evolutiva, Universitat de València, Paterna, Comunitat Valenciana, Spain.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Manzano-Marín
authors.affiliation: Department of Microbiology and Ecosystem Science, University of Vienna, Vienna, Austria.
authors.forename: Gitta
authors.initials: G
authors.lastname: Szabó
authors.affiliation: UMR1349 Institut de Génétique, Environnement et Protection des Plantes (IGEPP), Institut National de la Recherche Agronomique (INRA), Le Rheu, Bretagne, France.
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Simon
authors.affiliation: Department of Microbiology and Ecosystem Science, University of Vienna, Vienna, Austria.
authors.forename: Matthias
authors.initials: M
authors.lastname: Horn
authors.affiliation: Institut Cavanilles de Biodiversitat i Biologia Evolutiva, Universitat de València, Paterna, Comunitat Valenciana, Spain.|Área de Genómica y Salud de la Fundación para el fomento de la Investigación Sanitaria y Biomédica de la Comunitat Valenciana (FISABIO)-Salud Pública, València, Comunitat Valenciana, Spain.
authors.forename: Amparo
authors.initials: A
authors.lastname: Latorre
mesh_terms: D000818:Animals; D001042:Aphids / Q000382:microbiology* / Q000502:physiology; D020635:Buchnera / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D010802:Phylogeny; D012705:Serratia / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D013559:Symbiosis