Symbiont replacement and subsequent genome erosion reshape a dual obligate aphid symbiosis

Many insects rely on obligate microbial symbioses, often involving multiple partners. Although symbiont replacement is well-documented, how newly acquired and resident obligate symbionts adapt after such events remains unclear. Here, we investigate the dual obligate symbiosis of the aphid Lachnus tropicalis, where an ancestral Serratia lineage was replaced by a newly acquired another Serratia lineage while the primary symbiont Buchnera remained. Our metagenomic sequencing yielded complete genomes of Buchnera (0.42 Mb) and Serratia (2.8 Mb), revealing developing metabolic complementarity. Although the Serratia genome retained abundant gene sets for amino acid synthesis, it also contained pseudogenes in leucine and methionine pathways, which would be compensated for by Buchnera or the host. Comparison with L. roboris, which harbors the ancestral Serratia lineage, showed that the newly acquired Serratia in L. tropicalis exhibits identical tissue localization and vertical transmission patte..., , # Dataset: Symbiont replacement and subsequent genome erosion reshape a dual obligate aphid symbiosis (Dryad_upload_files.zip)

DOI: [https://doi.org/10.5061/dryad.4tmpg4fqm](https://doi.org/10.5061/dryad.4tmpg4fqm)

Manuscript Information

Journal: Proceedings of the Royal Society B (RSPB)

Manuscript Title: Symbiont replacement and subsequent genome erosion reshape a dual obligate aphid symbiosis

Authors: Tomonari Nozaki, Yuuki Kobayashi, Mika Ikeda, Shuji Shigenobu

### 1. Data Accessibility and External Repositories

All datasets generated and analyzed in this study are publicly available. Raw sequencing reads,including 16S rRNA amplicon sequences (DRR709987–DRR709998), Nanopore long reads (DRR718948), and Illumina short reads (DRR718949), have been deposited in the DDBJ Sequence Read Archive (DRA) under BioProject ID PRJDB35790. The primary raw sequencing data are further associated with BioSample ID: SAMD01601843. The assembled genome sequences of Buchnera aphidicola isolate Lt-N...,