Biology subjects

Perrier, A.

Publications and source records attributed to Perrier, A..

8 recordsLinked to original sources

bioRxiv2026

The extraordinary robustness of mitotic spindle assembly to microtubule dynamics plasticity revealed by end-binding proteins and tubulin tagging

Microtubules are dynamic, conserved cytoskeletal filaments that are essential for all eukaryotic cells. Microtubule dynamic properties are primarily characterized by measuring how fast they grow and shrink (growth and shrinkage rates) and how often they switch between assembly and disassembly (catastrophe and rescue frequencies). These four parameters measured for individual filaments can inform on the behavior of the entire microtubule network at the cell level. By comparing microtubule dynamics in Caenorhabditis elegans one-cell embryos using different genetically-encoded fluorescent probes, we observed an unexpected high variability in these parameters. Microtubule dynamics parameters were consistently higher in C. elegans strains expressing a fluorescently labelled microtubule end-binding protein than in strains relying on tubulin labelling, with microtubule growth rates differing by nearly a factor of two between the two conditions. This discrepancy was not limited to C. elegans, as we observed a similar effect in embryos of the tunicate Phallusia mammillata. Despite this, spindle size and assembly timing were only mildly affected. However, embryos expressing labelled end-binding protein exhibited higher frequency of mitotic defects and perturbed embryonic development upon exposure to various stresses such as elevated temperature or a compromised spindle assembly checkpoint. Thus, our work reveals both the remarkable robustness of mitotic spindle assembly in response to extreme microtubule dynamics plasticity, and the requirement for strict control of microtubule dynamics across successive early embryonic divisions. Our findings should also serve as a cautionary note when using tagged end-binding proteins to measure microtubule dynamics.

cell biology↗

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↗

bioRxiv2026

Adaptation to marginal habitats provides resilience to future warming at the rear edge

Rear-edge populations, relicts of glacial refugia, often persist in marginal habitats at the warmer edge of species distributions. Persistence in these habitats likely required adapting to postglacial climate warming. The resulting local adaptation may affect success in changing climates depending on whether adaptative strategies align or conflict with future conditions. We explored how rear-edge populations persist in their marginal habitats, and whether any adaptations affect responses to future warming in the North American herb Campanula americana. We raised plants from 23 rear-edge and central populations in a common garden experiment spanning their climatic gradient. We evaluated performance across sites and life stages to identify key traits underlying adaptation to rear-edge conditions. We then predicted the expression of key traits under future climates. Local adaptation at the rear edge was mainly driven by whether plants were able to transition from vegetative growth to reproduction, i.e. bolting. Rear-edge populations exhibited high bolting frequency under local warm winters, while more northern populations failed to bolt in these conditions. Bolting is cued by winter cold (vernalization) in the species, but rear-edge climates provide only few days sufficiently cold for effective vernalization. We found that rear-edge populations have adapted to these conditions by evolving reduced vernalization requirement and sensitivity. Under projected warmer winters, bolting is expected to decline at mid-latitudes, whereas rear-edge populations are predicted to maintain high bolting. Our findings highlight that adaptation to marginal rear-edge habitats can hinge on a single trait, and this adaptation may buffer rear-edge populations against future climates.

evolutionary biology↗

bioRxiv2025

Heterogeneous evolutionary history defines the rear edge of the North American herb Campanula americana

AimWarmer range limits of species distributions offer a window into the ecological and evolutionary processes associated with long-term warming, as they often harbor relicts of refugial populations from last glaciation. However, warm-edge populations vary in their refugial, evolutionary, and climatic histories, complicating their use as models. Here, we characterize this variation at the warmer range limit of the North American herb Campanula americana. LocationEastern North America TaxonCampanula americana MethodsWe evaluated the warmer range limit using species distribution model hindcasting, range-wide analyses of population structure, effective migration and phylogenetic relationships. ResultsWarm-edge populations vary in their refugial history; most are relicts of historic refugial populations (i.e. rear edge), but some result from southward postglacial colonization. Within the rear edge, populations exhibit pronounced genetic structure, forming highly isolated clusters despite contiguous geography and only modest landscape barriers. Distinct rear-edge clusters also varied in climate history and gene flow among population, with the more southern populations experiencing higher habitat decline, fragmentation and isolation. Finally, only rear-edge populations from northern refugial areas contributed to postglacial range expansion. Main conclusionsOur study highlights the challenges of using warm-edge populations as ecological and evolutionary models of response to climate change. Even in a geographically simple setting, warm-edge populations exhibit refugial, genetic, and climatic heterogeneity. Characterizing this variation is essential for accurately identifying rear-edge populations and inferring their evolutionary history. Knowledge of the contribution of warm-edge populations to range-wide genetic variation is key when considering how these populations may inform studies of adaptation to future climate change.

evolutionary biology↗

bioRxiv2025

The legacy of past climate warming: strong local adaptation in rear-edge populations

Improving forecasts of species responses to climate change has become a central challenge in ecology and evolution as species distributions are increasingly disrupted by ongoing climate warming. Insight into this challenge may be gained through a better understanding of evolutionary responses to past climate change. The rear edges of species distributions are typically relict populations persisting in former glacial refugia at warmer range limits. As such, they form natural laboratories to study the evolutionary outcomes of past climate warming. Three such outcomes have been proposed for rear-edge populations: maintenance of high diversity due to long-term persistence, strong genetic drift following habitat decline, and strong local adaptation allowing persistence despite environmental change. Empirical studies rarely explicitly test these alternate outcomes limiting our understanding of evolutionary responses to warming climates. We tested all three evolutionary outcomes at the rear edge of the North American herb Campanula americana, by assessing genetic variation in a genome-wide population genetic study, drift load as measure of fitness decline due to drift in a controlled crossing study, and local adaptation in a transplant study. Rear-edge populations exhibited reduced genetic diversity within populations and high differentiation among populations, typically interpreted as evidence of genetic drift, yet show limited drift load. Instead, these populations expressed strong local adaptation, thriving in rear-edge habitats that were unsuitably warm for populations in the expanded range. This indicates that warm-edge populations may persist under warming climates by gradually adapting, even in the face of genetic erosion. Our findings highlight the importance of explicitly testing for all evolutionary outcomes, and particularly going beyond measures of genetic variation, when inferring evolutionary history. More broadly, these findings identify rear-edge populations not as relics of decline, but as underappreciated models for studying successful adaptation under long-term climate change.

evolutionary biology↗

bioRxiv2025

Functional interplay between (p)ppGpp and RNAP in Acinetobacter baumannii

The (p)ppGpp-dependent stress response is required for pathogenic bacteria to survive both outside and inside the host but the mechanisms behind this survival are mostly unknown. In this study, we characterize the (p)ppGpp metabolism in the opportunistic pathogen multi-drug-resistant Acinetobacter baumannii. We show that two stressful conditions potentially encountered during infection - iron starvation and polymyxin exposure - induce (p)ppGpp production. The absence of (p)ppGpp led to multiple consequences on the physiology of A. baumannii, including an increase of surface motility, a decrease in catalase activity, a poor survival upon nutrient starvation, a rapid killing during desiccation and a strong attenuation in a Galleria mellonella model of infection. Using a motility suppressor screen, we isolated multiple independent stringent mutations in rpoB and rpoC that suppress the (p)ppGpp-dependent phenotypes. By combining the suppressor screen with deep sequencing, we isolated dozens of additional mutants, expanding the list of putative stringent RNAP mutations described so far. Furthermore, our transcriptomic data reveal that (p)ppGpp deeply impacts the transcriptional landscape of A. baumannii on solid surface to induce many stress-related genes, including catalase and hydrophilins critical for tolerance to desiccation. This work highlights the functional interplay between (p)ppGpp and RNAP in the successful survival of A. baumannii in the environment but also during infection.

microbiology↗

bioRxiv2024

Shifts in vernalization and phenology at the rear edge hold insight into adaptation of 1 temperate plants to future milder winters

O_LITemperate plants often regulate reproduction through winter cues, such as vernalization, that may decrease under climate change. Studies of rear-edge populations, glacial relicts that persist in environments that have warmed since last glaciation, can provide insight into adaptive potential to milder winters. C_LIO_LIWe studied how rear-edge populations have adapted to shorter winters and compared them to the rest of the range in the herb Campanula americana. Using citizen science, climate data and experimental climate manipulation, we characterize variation in vernalization requirements and reproductive phenology across the range and their potential climatic drivers. C_LIO_LIRear-edge populations experienced little to no vernalization in nature. In climate manipulation experiments, these populations also had a reduced vernalization requirement, weaker response to changes in vernalization length, and flowered later compared to the rest of the range. C_LIO_LIOur results suggest shifts in phenology and its underlying regulation at the rear edge to compensate for unreliable vernalization cues. Thus, future milder winters may be less detrimental to these populations than more northern ones. Furthermore, our results showcase strong adaptive shifts at the rear edge of temperate plants ranges, highlighting the importance of these areas in studies of predicted future climates. C_LI

evolutionary biology↗

bioRxiv2021

Environment-dependent expression of mutational load and species' range limits

Theoretical and empirical research on the causes of species range limits suggests the contribution of several intrinsic and extrinsic factors, with potentially complex interactions among them. An intrinsic factor proposed by recent theory is mutational load increasing towards range edges because of genetic drift. Furthermore, environmental quality may decline toward range edges and enhance the expression of load. Here we tested whether the expression of mutational load associated with range limits in the North American plant Arabidopsis lyrata is enhanced under stressful environmental conditions by comparing the performance of within- versus between-population crosses at common garden sites across the species distribution and beyond. Heterosis, reflecting the expression of load, increased with heightened estimates of genomic load and with environmental stress caused by warming, but the interaction was not significant. We conclude that range-edge populations suffer from a twofold genetic Allee effect caused by increased mutational load and stress-dependent load linked to general heterozygote deficiency, but no synergistic effect between them.

evolutionary biology↗