Communication Dans Un Congrès Année : 2025

A selective bottleneck during host entry drives the evolution of new plant symbionts

David Roche

Résumé

The acquisition of mobile genetic elements (MGEs) can trigger radical shifts in microbial lifestyles, for example by converting a mutualist into a pathogen or vice versa. These transitions often involve changes in host range, infection strategies, or ecological niches, which typically require specific adaptations to the different stages of the new life cycle. While comparative genomic studies have documented several MGE-associated lifestyle transitions, a detailed understanding of the tempo and mode of adaptation to new symbiotic lifestyles is still lacking.

Here, we sought to evolve new nitrogen-fixing bacterial symbionts of the legume plant Mimosa pudica from an ancestral plant pathogenic bacterium, Ralstonia solanacearum, which was engineered with a plasmid carrying essential symbiosis genes. We experimentally evolved this strain for over 900 generations during serial passages through a simplified symbiotic life cycle (comprising rhizosphere inoculation, root entry, and within-plant proliferation) and characterized the dynamics of molecular and phenotypic adaptation in the evolved populations.

Multiple independent lineages exhibited rapid and parallel fitness increase during their interaction with M. pudica. Whole-population sequencing revealed a continuous accumulation of mutations, facilitated by a plasmid-induced transient hypermutagenesis phase before host entry. We observed sequential sweeps of mutational cohorts, with multiple adaptive mutations co-occurring within these cohorts. Notably, all adaptive mutations enhanced host entry, while only a subset also improved within-host proliferation. Computational modelling suggests that this pattern is a consequence of the strong selective bottleneck occurring at host entry and immediately following the hypermutagenesis phase. Our findings highlight how selective bottlenecks shape adaptive trajectories of symbiotic bacteria experiencing complex infection processes.

Recherche Data Gouv

Est documentée par 10.15454/QYB2S9 Jeu de données Remigi, Philippe; Doin de Moura, Ginaini Grazielli; Ferdy, Jean-Baptiste; Capela, Delphine, 2022, "Supplementary data for "A selective bottleneck during host entry drives the evolution of new legume symbionts"", https://doi.org/10.15454/QYB2S9, Recherche Data Gouv, V1, UNF:6:7V6UpbvEH0Dv11w6XUoz5w== [fileUNF]

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Recherche Data Gouv

Est documentée par 10.15454/QYB2S9 Jeu de données Remigi, Philippe; Doin de Moura, Ginaini Grazielli; Ferdy, Jean-Baptiste; Capela, Delphine, 2022, "Supplementary data for "A selective bottleneck during host entry drives the evolution of new legume symbionts"", https://doi.org/10.15454/QYB2S9, Recherche Data Gouv, V1, UNF:6:7V6UpbvEH0Dv11w6XUoz5w== [fileUNF]

Raw data and code
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Dates et versions

hal-05314854 , version 1 (14-10-2025)

Identifiants

  • HAL Id : hal-05314854 , version 1

Citer

Ginaini Doin de Moura, Saida Mouffok, Nil Gaudu, Anne-Claire Cazalé, Marine Milhes, et al.. A selective bottleneck during host entry drives the evolution of new plant symbionts. Congress of the European Society for Evolutionnary Biology, European Society for Evolutionnary Biology (ESEB), Aug 2025, Barcelona, Spain. ⟨hal-05314854⟩
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