Biology subjects

Capela, D.

Publications and source records attributed to Capela, D..

5 recordsLinked to original sources

bioRxiv2026

SpoT-mediated reduction of (p)ppGpp levels promotes Ralstonia pseudosolanacearum adaptation to both plant xylem and legume nodules

During evolution, bacteria have developed the ability to interact intimately with eukaryotic hosts. These interactions span a dynamic continuum ranging from pathogenicity to mutualism, along which bacteria can rapidly evolve and shift their lifestyles. However, the molecular mechanisms that enable bacteria to adapt to new hosts and to transition between distinct interaction modes remain poorly understood. Here, using a unique combination of two independent evolution experiments, we identified and characterized parallel adaptive mutations in spoT, which encodes the bifunctional (p)ppGpp synthetase-hydrolase. These mutations promote the adaptation of the plant pathogen Ralstonia pseudosolanacearum to two distinct plant-associated environments and two distinct lifestyles, the xylem of both susceptible and tolerant host plants as a pathogen and the root nodules of a legume as a symbiont, without compromising virulence on susceptible hosts. These mutations enhance the utilization of multiple carbon and nitrogen sources, including substrates known to be abundant in xylem sap, and increase bacterial exponential growth rate in minimal medium, suggesting reduced basal (p)ppGpp levels. Assessment of a strain deficient in SpoT synthetase activity confirmed that lowering basal (p)ppGpp levels is adaptive in both plant environments. Together, our findings reveal that fine-tuning intracellular (p)ppGpp concentrations represents an efficient strategy for optimizing bacterial adaptation to complex host-associated environments.

microbiology↗

bioRxiv2025

Environmental complexity constrains evolutionary adaptation across taxa

Complex environments combining multiple stressors are the new norm worldwide. Adaptive evolution will be critical to population persistence under these combined challenges, but how environmental complexity affects the pace of evolution remains poorly understood. Using a meta-experimental evolution approach, we exposed 14 species, from bacteria to unicellular eukaryotes and plants, to single stressors and their pairwise combinations for multiple generations, while keeping the overall stress level comparable. Populations evolving under combined stressors tended to have lower fitness increase in the selective environments, higher fitness reductions in the control environment, and shallower relation between initial maladaptation and fitness gain, than under single stressors. However, these responses varied with species and stressor type. Accounting for such constraints on evolutionary dynamics should prove crucial for the management of biodiversity. Significance StatementA pressing challenges for modern science and society in the face of ongoing global change is understanding what limits the capacity of living organisms to adapt to complex environments combining multiple stressors. To answer to this question, we conducted a large-scale meta-experimental evolution design across a diversity of organisms, exposing them for multiple generations to either single or combined-stress treatments. Combined stressors led to less adaptive fitness gain than single stressors, and imposed additional costs through reduced fitness in non-stressful conditions. This unique combination of meta-experimental approach with a careful distinction between environmental complexity and overall stress allowed us to gain robust quantitative evidence on how environmental complexity can impact the pace of evolution.

evolutionary biology↗

bioRxiv2022

Comparative phylotranscriptomics reveals a 110 million years-old symbiotic program

Symbiotic interactions have structured past and present ecosystems and shaped the evolution of life. As any trait, the symbiotic state observed in extant species builds on ancestral and conserved features, and lineage-specific innovations. From these mixed origins, defining the ancestral state of symbiotic associations is challenging although it is instrumental for understanding how symbiotic abilities emerge from non-symbiotic states. Here we aimed at reconstructing the intermediate steps leading to the root-nodule nitrogen-fixing symbiosis (RNS) observed in some extant flowering plants. For this, we compared the transcriptomic responses of nine host plants in response to symbiotic bacteria. We included the mimosoid legume Mimosa pudica for which we assembled a chromosome-level genome and generated the transcriptomic response to experimentally evolved bacterial symbionts. With this dataset, we reconstructed the ancestral RNS transcriptome, composed of most already described symbiotic genes together with hundreds of novel candidates. We found that the response to the chemical signals produced by the symbiont, nodule organogenesis and nitrogen-fixation are predominantly linked to ancestral responses, although these traits have diversified in the different nitrogen-fixing lineages. We detected a clear signature of recent and convergent evolution for the ability to release intracellular symbiosomes in two legume lineages, exemplified by the expression of different classes of small proteins in each group, potentially leading to the convergent gain of symbiotic evolutionary stability. Our findings demonstrate that most of the novelties for RNS were mostly in place in the most recent common ancestor of the RNS-forming species that lived on Earth 110 million years ago. Graphical abstractA little graphical/nice phylogeny with nodes of interest HighlightsO_LIWe sequenced a high-quality genome of the Mimosoideae Mimosa pudica C_LIO_LIThe nitrogen-fixing root-nodule symbiosis relies on an ancestral transcriptomic response C_LIO_LIAll symbiotic traits involve genes of the ancestral symbiotic program C_LIO_LISymbiont perception, nodule organogenesis and nitrogen-fixation are essentially ancestral processes C_LIO_LIConvergent evolution of intracellular accommodation of symbionts additionally involves lineage-specific genes C_LI

plant biology↗

bioRxiv2022

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

During the emergence of new host-microbe symbioses, multiple selective pressures-acting at the different steps of the microbial life cycle-shape the phenotypic traits that jointly determine microbial fitness. However, the relative contribution of these different selective pressures to the adaptive trajectories of microbial symbionts are still poorly known. Here we characterized the dynamics of phenotypic adaptation and its underlying genetic bases during the experimental evolution of a plant pathogenic bacterium into a legume symbiont. We observed that fast adaptation was predominantly driven by selection acting on competitiveness for host entry, which outweighed selection acting on within-host proliferation. Whole-population sequencing of evolved bacteria revealed that phenotypic adaptation was supported by the continuous accumulation of new mutations and the sequential sweeps of cohorts of mutations with similar temporal trajectories. The identification of adaptive mutations within the fixed mutational cohorts showed that all of them improved competitiveness for host entry, while only a subset of those also improved within host proliferation. Computer simulations predict that this effect emerges from the presence of a strong selective bottleneck at host entry. Together, these results show how selective bottlenecks can alter the relative influence of selective pressures acting during bacterial adaptation to multistep infection processes.

evolutionary biology↗

bioRxiv2018

Parallels between experimental and natural evolution of legume symbionts

The emergence of symbiotic interactions has been studied using population genomics in nature and experimental evolution in the laboratory, but the parallels between these processes remain unknown. We compared the emergence of rhizobia after the horizontal transfer of a symbiotic plasmid in natural populations of Cupriavidus taiwanensis, over 10 MY ago, with the experimental evolution of symbiotic Ralstonia solanacearum for a few hundred generations. In spite of major differences in terms of time-span, environment, genetic background and phenotypic achievement, both processes resulted in rapid diversification dominated by purifying selection concomitant with acquisition of positively selected mutations. The latter were lacking in the plasmid carrying the genes responsible for the ecological transition. Instead, adaptation targeted the same set of genes leading to the cooption of the same quorum-sensing system. Our results provide evidence for similarities in experimental and natural evolutionary transitions and highlight the potential of comparisons between both processes to understand symbiogenesis.

evolutionary biology↗