Biology subjects

Joly, S.

Publications and source records attributed to Joly, S..

7 recordsLinked to original sources

bioRxiv2025

Wnt signaling modulates tissue mechanics, actin order, and regeneration in Hydra vulgaris

Hydra vulgaris is a powerful model organism in the study of axial patterning and regeneration. While recent models emphasize the importance of mechanical cues in establishing the body axis of Hydra tissue spheres, the precise role of the Wnt pathway, known to be central to axial patterning, in regulating tissue mechanics and cytoskeletal organization remains unclear. In this paper, we pharmacologically modulated the canonical Wnt pathway using Alsterpaullone and iCRT14 and assessed their effects on regeneration, tissue rheology, osmotic oscillations and actin organization in Hydra tissue spheres. We found that Wnt activation prevents full regeneration, softens the constitutive tissues, disrupts osmotic oscillations, leads to an accumulation of dense actin filaments but impairs their orientational order. Conversely, we found that Wnt inhibition partially impairs regeneration and reduces actin filament presence while preserving alignment. These results support the underlying hypotheses of two existing mechano-chemical models of Hydra patterning, suggesting that Wnt-driven feedbacks on both tissue stiffness and actin order could contribute to the robust emergence of body axes. Our findings highlight the possibility of redundant and coupled mechanisms in the Hydra patterning system, potentially explaining its robustness.

biophysics↗

bioRxiv2025

Urbanization drives genetic and plastic responses of the spotted jewelweed flower morphology

The spectacular diversity of flowers is largely driven by pollinator-mediated selection that favors attractive flowers and effective pollen transfer. Urbanization has the potential to affect floral trait evolution by altering pollinator communities through environmental changes. Additionally, abiotic changes in urban habitats can induce phenotypic plasticity, further shaping evolutionary trajectories. We investigated how urbanization affects the genetic and plastic components of flower morphology of Impatiens capensis across four Canadian cities. We found that urbanization influenced the pollinator community composition and the body size of bumblebees, the species main pollinator, although the magnitude of the size effect varied among cities. Using a combination of field surveys and a common garden experiment, our results suggest that urbanization affects sepal size - a tubular floral organ in which pollinators enter to access the nectar - through both genetic and plastic responses. While plasticity sometimes masked the genetic determination of sepal size in the field, we observed a positive correlation between the genetic component of the sepal size and bumblebee body size. These results suggest that urban habitats may drive evolutionary changes in floral traits by modifying pollinator communities.

evolutionary biology↗

bioRxiv2025

Global characterization of Dictyostelium discoideum gene expression changes under hypoxic conditions

Aerobic eukaryotes utilize O2 to oxidize metabolites and generate ATP. The protist kingdom lacks the Hypoxia Inducible Factor-dependent transcriptional response network to accommodate low O2 though possesses a HIF prolyl hydroxylase that initially mediates the response. To address the scale and scope of hypoxic responses in protists, we characterized transcriptomic and proteomic changes when the social amoeba Dictyostelium is subjected to low (1%) O2 under nutritive conditions over 24 h followed by reoxygenation. Remarkably, 32% of the transcripts quantified were differentially expressed during hypoxia, with greatest changes associated with early (1 h) and late phases (24 h). Protein changes were modestly correlated with and generally lagged behind transcriptional changes. Correlated changes were observed for transcripts and proteins associated with various metabolic, anabolic, and catabolic pathways, as well as chromosome organization, cell cycling, vesicular trafficking, and signaling. Analysis of 4 marker genes showed extremely rapid responses that were graded over a range of O2 levels, with differential responses to inhibitors affecting protein synthesis and mitochondria. Overall, the amoebal response to a low but non-toxic O2-level resulted in massive remodeling of the transcriptome and proteome.

genomics↗

bioRxiv2023

Latitudinal gradients in predation persist in urban environments

Urbanization can profoundly disrupt local ecology. But while urban areas now stretch across latitudes, little is known about urbanizations effects on macroecological patterns. We used standardized experiments to test whether urbanization disrupts latitudinal gradients in seed predation, a macroecological pattern that shapes community assembly and diversity. Using >56,000 seeds, we compared predation in urbanized and natural areas across 14,000 km of latitude, spanning the Americas. Predation increased 5-fold from high latitudes to the tropics, and latitudinal gradients in predation persisted in urban areas despite significant habitat modification. Urbanization reduced predation by vertebrates, but not invertebrates, and seemed to increase ant predation specifically. Our results show that macroecological patterns in predation intensity can persist in urbanized environments, even as urbanization alters the relative importance of predators. One-Sentence SummaryAcross 56,000 seeds and 112{degrees} of latitude, latitudinal gradients in seed predation are equally strong in natural vs. urban areas

ecology↗

bioRxiv2023

Epigenetic and physiological alterations in zebrafish subjected to hypergravity

Gravity is one of the most constant environmental factors across Earths evolution and all organisms are adapted to it. Consequently, spatial exploration has captured the interest in studying the biological changes that physiological alterations are caused by gravity. In the last two decades, epigenetics has explained how the environmental cues are able to altered gene functions in the organisms. Although many studies addressed gravity, the underlying biological and molecular mechanisms that are occurred in altered gravity for those epigenetics-related mechanisms, are mostly inexistent. The present study addressed the effects of hypergravity on development, behavior, gene expression, and most importantly, on the epigenetic changes in a world-wide animal model, the zebrafish (Danio rerio). To perform hypergravity experiments, a custom-centrifuge simulating the large diameter centrifuge (100 rpm [~] 3 g) were designed and zebrafish embryos were exposed during 5 days post fertilization (dpf). Results showed a significant decrease of survival at 2 dpf but not significance in the hatching rate. Physiological and morphological alterations including fish position, movement frequency and swimming behavior showed significant changes due to hypergravity. Epigenetic studies showed a significant hypermethylation of the genome of the zebrafish larvae subjected to 5 days of hypergravity. A downregulation of the gene expression of three epigenetic-related genes (dnmt1, dnmt3, and tet1), although not significant, were further observed. Taken altogether, gravity alterations affected biological responses including epigenetics in fish, providing a valuable roadmap of the putative hazards of living beyond Earth.

cell biology↗

bioRxiv2019

Immune genes, IL1β and Casp9, show sexual dimorphic methylation patterns in the zebrafish gonads

There is a crosstalk between the immune and the reproductive systems in which sexual dimorphism is a common pattern in vertebrates. In the last years, epigenetics has emerged as a way to study the molecular mechanisms involved during gonadal development, which are responsible to integrate environmental information that contributes to assign a specific sexual phenotype (either an ovary or a testis). In the fish gonads, it is known of the existence of the reproduction-immune system interactions although the epigenetic mechanisms involved are far to be elucidated. Here, we used the zebrafish (Danio rerio) as a model to study the DNA methylation patterns of two well-known innate immune genes: IL1{beta} and Casp9. DNA methylation levels were studied by a candidate gene approach at single nucleotide resolution and further, gene expression analysis were carried out. Results showed that there was clear sexual dimorphism in the DNA methylation levels of the two immune studied genes, being significantly higher in the testes when compared to the ovaries. In summary, and although much research is needed, here we present two potential candidates as epimarkers with forthcoming applications in the livestock and fish farming production, for example, in immune fish diseases or sexual control programs.

immunology↗

bioRxiv2018

On the importance of accounting for intraspecific genomic relatedness in multi-species studies

1. Analyses in many fields of ecology are increasingly considering multiple species and multiple individuals per species. Premises of statistical tests are often violated with such datasets because of the non-independence of residuals due to phylogenetic relationships or intraspecific population structure. Comparative approaches that account for the phylogenetic relationship of species--for which the benefits are demonstrated--are well developed. However, the importance of accounting for the intraspecific genetic structure, especially with the phylogenetic structure, is rarely addressed in the ecological literature.\n\n2. We investigated whether it is beneficial to account for intraspecific genomic relatedness in multi-species studies. For this, we used a Phylogenetic Mixed Model to analyze simulated data and results from a budburst experiment where clippings of 10 tree and shrub species were subjected to different treatments in terms of temperature and photoperiod.\n\n3. We found that accounting for intraspecific genomic relatedness yields more accurate and precise fixed effects as well as increased statistical power, but more so when the relative importance of the intraspecific to the phylogenetic genetic structure is greater. Analysis of the budburst experiment further showed that accounting for intraspecific and phylogenetic structures yields improved estimates of warming and photoperiod effects and their interactions in explaining the time to budburst.\n\n4. Our results show that important statistical gains can be made by incorporating information on the intraspecific genomic relatedness of individuals in multi-species studies. This is relevant for investigations that are interested in intraspecific variation and that plan to include such observations in statistical tests.

ecology↗