Latorre, Amparo

Summary 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.

ABSTRACT The genome of “ Candidatus Portiera aleyrodidarum,” the primary endosymbiont of the whitefly Bemisia tabaci (Mediterranean species), is reported. It presents a reduced genome (357 kb) encoding the capability to synthetize, or participate in the synthesis of, several amino acids and carotenoids, being the first insect endosymbiont capable of supplying carotenoids.

ABSTRACT The sequence of the genome of “ Candidatus Tremblaya princeps” strain PCVAL, the primary endosymbiont of the citrus mealybug Planococcus citri , has been determined. “ Ca . Tremblaya princeps” presents an unusual nested endosymbiosis and harbors a gammaproteobacterial symbiont within its cytoplasm in all analyzed mealybugs. The genome sequence reveals that “ Ca . Tremblaya princeps” cannot be considered an independent organism but that the consortium with its gammaproteobacterial symbiotic associate represents a new composite living being.

ABSTRACT Buchnera aphidicola BCc, the primary endosymbiont of the aphid Cinara cedri (subfamily Lachninae), is losing its symbiotic capacity and might be replaced by the coresident “ Candidatus Serratia symbiotica.” Phylogenetic and morphological analyses within the subfamily Lachninae indicate two different “ Ca . Serratia symbiotica” lineages and support the longtime coevolution of both symbionts in C. cedri .