Biology subjects

Joncour, P.

Publications and source records attributed to Joncour, P..

8 recordsLinked to original sources

bioRxiv2022

Asexual male production by ZW recombination in Artemia parthenogenetica

In some asexual species, parthenogenetic females occasionally produce males, which may strongly affect the evolution and maintenance of asexuality if they cross with related sexuals and transmit genes causing asexuality to their offspring ("contagious parthenogenesis"). How these males arise in the first place has remained enigmatic, especially in species with sex chromosomes. Here, we test the hypothesis that rare, asexually produced males of the crustacean Artemia parthenogenetica are produced by recombination between the Z and W sex chromosomes during non-clonal parthenogenesis, resulting in ZZ males through loss of heterozygosity at the sex determination locus. We used RAD-sequencing to compare asexual mothers with their male and female offspring. Markers on several sex-chromosome scaffolds indeed lost heterozygosity in all male but no female offspring, suggesting that they correspond to the sex-determining region. Other sex-chromosome scaffolds lost heterozygosity in only a part of the male offspring, consistent with recombination occurring at a variable location. Alternative hypotheses for the production of these males (such as partial or total hemizygosity of the Z) could be excluded. Rare males are thus produced because recombination is not entirely suppressed during parthenogenesis in A. parthenogenetica. This finding may contribute to explaining the maintenance of recombination in these asexuals.

evolutionary biology↗

bioRxiv2021

Beneficial Lactiplantibacillus plantarum promote Drosophila growth by down-regulating the expression of PGRP-SC1

Animals and their commensal bacteria are known to reciprocally influence many traits of their physiology. Specifically, microbes contribute to the maintenance of the immune system homeostasis, improve host digestive processes, and sustain host growth and development. Several studies have reported that such effects result from an intricate network of nutritional, metabolic and immune inputs and partly rely on the capacity of microbes to regulate the hosts transcriptional response. However, these evidences mainly come from comparing the transcriptional response caused by commensal bacteria with that of axenic animals, making it difficult to identify the specific animal genes that are regulated by beneficial microbes. Here, we employ a well-established model of nutritional symbiosis, Drosophila melanogaster associated with Lactiplantibacillus plantarum, to understand the host genetic pathways regulated by beneficial bacteria and leading to improved host growth and development. Using isogenic L. plantarum strains bearing different growth-promoting effects, we show that the microbial benefit to the host relies on the down-regulation of peptidoglycan- recognition proteins. In particular, we report that the lower expression of PGRP-SC1 exerted by growth-promoting bacteria is responsible for their higher proliferation and the consequent increased production of beneficial metabolites, which ultimately leads to improved host growth and development. Our study helps elucidate the mechanisms underlying the beneficial effect exerted by commensal bacteria, defining the role of PGRP-SC1 in the relationship between Drosophila and its gut microbes. IMPORTANCECommensal bacteria are in constant association with their animal hosts, significantly affecting animal physiology through an intricate network of nutritional, metabolic and immune inputs. Yet, how beneficial bacteria specifically improve animal health is not fully understood. Here, we used a well-established model of nutritional symbiosis to understand how beneficial gut microbes improve host growth via regulation of its transcriptional response. Our study advances the current knowledge in host-microbe interactions by demonstrating that commensal bacteria improve fly growth by actively regulating the expression of immune effectors, which lead to higher immune tolerance. This leads to higher bacterial proliferation and the increased production of beneficial microbial metabolites, which are then consumed by the host. Our results shed light on the complex mechanisms underlying the relationships between a host and its gut microbes.

microbiology↗

bioRxiv2021

Strong transgenerational effects but no genetic adaptation in zooplankton 24 years after an abrupt +10°C climate change

The climate is currently warming fast, threatening biodiversity all over the globe. Adaptation is often rapid when the environment changes quickly, but for climate warming very little evidence is available. Here, we investigate the pattern of adaptation to an extreme +10{degrees}C climate change in the wild, following the introduction of brine shrimp Artemia franciscana from San Francisco Bay, USA, to Vinh Chau saltern in Vietnam. We use a resurrection ecology approach, hatching diapause eggs from the ancestral population and the introduced population after 13 and 24 years (resp. ~54 and ~100 generations). In a series of coordinated experiments, we determined whether the introduced Artemia show increased tolerance to higher temperatures, and the extent to which genetic adaptation, developmental plasticity, transgenerational effects, and local microbiome differences contributed to this tolerance. We find that introduced brine shrimp do show increased phenotypic tolerance to warming. Yet strikingly, these changes do not have an additive genetic component, are not caused by mitochondrial genetic variation, and are not caused by epigenetic marks set by adult parents exposed to warming. Further, we do not find any developmental plasticity in response to warming, nor any protective effect of heat-tolerant local microbiota. We conclude that the evolution of shrimps extreme thermal tolerance is only due to transgenerational (great)grandparental effects, possibly epigenetic marks set by parents who were exposed to high temperatures as juveniles. This finding challenges standard models of genetic and plastic adaptive responses, and our conception of how species may cope with climate warming. Significance statementAdaptation is often rapid when environments change quickly, but for climate warming little evidence is available. Many studies report no genetic responses due to pre-existing plasticity, while others point towards epigenetics and microbiota effects. In this study, we take advantage of a natural experiment to study all of these effects. We use a set of coordinated experiments and a resurrection ecology approach, reviving resting eggs of brine shrimp up to100 generations after their introduction from a temperate to a tropical saltern. We find that heat adaptation occurs, but heritability is fully "missing". Plasticity and microbiota play no role either, indicating that only transgenerational (great)grandmaternal effects are involved. This finding prompts us to reconsider the relative importance of the different possible mechanisms by which phenotypic change can occur, especially in response to temperature variation.

evolutionary biology↗

bioRxiv2020

Papillary And Reticular Fibroblasts Generate Distinct Microenvironments That Differentially Impact Angiogenesis

Papillary and reticular dermis show distinct extracellular matrix (ECM) and vascularization, and fibroblasts isolated from these compartments have different gene expression patterns and behaviour in vitro. However, due to lack of relevant models, the contribution of skin fibroblast sub-populations to vascularization remains unknown. We thus cultured human papillary and reticular fibroblasts as cell sheets. Differential transcriptomic analysis was performed by RNA sequencing to characterize their microenvironment. Bioinformatic analysis revealed that each fibroblast population expressed specific angiogenesis and matrisome gene expression signatures resulting in specific ECM that differed both in composition and structure. The impact of secreted and ECM-bound factors was then assessed using 3D angiogenesis assays. When co-cultivated with endothelial cells, the papillary and reticular microenvironments induced the formation of distinct capillary networks mimicking the characteristics of vasculature of native dermis subcompartments (vessel diameter and density, number of branch points). Whereas conditioned media of papillary fibroblasts displayed intrinsic high angiogenic potential, reticular ones only contributed to capillary formation induced by exogenous VEGF. These results show that skin fibroblast populations regulate angiogenesis via both secreted and ECM-bound factors. Our work emphasizes the importance of papillary and reticular fibroblasts, not only for modelling dermis microenvironment but also for its vascularization.

cell biology↗

bioRxiv2018

Commensal bacteria act as a broad genetic buffer in Drosophila during chronic under-nutrition

Eukaryotic genomes encode several well-studied buffering mechanisms that robustly maintain invariant phenotypic outcome despite fluctuating environmental conditions. Here we show that the gut microbiota, represented by a single Drosophila facultative symbiont, Lactobacillus plantarum (LpWJL), acts also as a broad genetic buffer that masks the contribution of the cryptic genetic variations in the host under nutritional stress. During chronic under-nutrition, LpWJL consistently reduces variation in different host phenotypic traits and ensures robust organ patterning; LpWJL also decreases genotype-dependent expression variation, particularly for development-associated genes. We further demonstrate that LpWJL buffers via reactive oxygen species (ROS) signaling whose inhibition severely impairs microbiota-mediated phenotypic robustness. We thus identified an unexpected contribution of facultative symbionts to Drosophila fitness by assuring developmental robustness and phenotypic homogeneity in times of nutritional stress.

developmental biology↗

bioRxiv2017

Bacterial adaptation to host diet is a key evolutionary force shaping host-microbe symbiosis

Life on Earth was dominated by bacteria for billions of years1. About 600 million years ago, animal life emerged and micro-organisms played a crucial role in shaping animal development, physiology and evolution2-4. The two partners committed to a symbiotic relationship that persists in nearly all animals today. Such beneficial interactions are pervasive throughout nature and have been extensively characterized5,6. However, the ecological and evolutionary forces that drive the emergence and evolution of the symbiont benefits to their animal hosts remain largely elusive. Here we show that the host nutritional environment, instead of the host, is a predominant driving force in this evolutionary process and we identify a mechanism resulting from the bacterial adaptation to the diet, which confers improved functional benefit to the host. By applying experimental evolution to a model of host-bacteria beneficial symbiosis: Drosophila melanogaster associated with Lactobacillus plantarum, one of its growth promoting symbiotic bacteria7,8, we found that the de novo mutations in the same acetate kinase (ackA) locus invariably emerge first, rapidly become fixed, and such evolution occurs with or without the host. Furthermore, we demonstrate that ackA mutations trigger the increased production of N-acetyl-glutamine, which is sufficient to confer improved host growth capabilities to the evolved bacterial strains. Our study therefore identifies a specific mechanism by which a symbiotic bacterium increases its benefit to its animal host and reveals that adaptation to the host diet is a foremost step in the determination of the evolutionary course of symbiosis between an animal and its gut microbes.

evolutionary biology↗

bioRxiv2017

Stable association of a Drosophila-derived microbiota with its animal partner and the nutritional environment upon transfer between populations and generations

In the past years, the fruit fly Drosophila melanogaster has been extensively used to study the relationship between animals and their associated microbes. Compared to the one of wild populations, the microbiota of laboratory-reared flies is less diverse, and comprises fewer bacterial taxa; nevertheless, the main commensal bacteria found in fly microbiota always belong to the Acetobacteraceae and Lactobacillaceae families. The bacterial communities associated with the fly are environmentally acquired, and the partners engage in a perpetual re-association process. Adult flies constantly ingest and excrete microbes from and onto their feeding substrate, which are then transmitted to the next generation developing within this shared habitat. We wanted to analyze the potential changes in the bacterial community during its reciprocal transfer between the two compartments of the niche (i.e. the fly and the diet). To address this question, we used a diverse, wild-derived microbial community and analyzed its relationship with the fly population and the nutritive substrate in a given habitat. Here we show that the community was overall well maintained upon transmission to a new niche, to a new fly population and to their progeny, illustrating the stable association of a Drosophila-derived microbiota with its fly partner and the nutritional environment. These results highlight the preponderant role of the nutritional substrate in the dynamics of Drosophila/microbiota interactions, and the need to fully integrate this variable when performing such studies.

microbiology↗

bioRxiv2017

D-Alanine esterification of teichoic acids contributes to Lactobacillus plantarum mediated intestinal peptidase expression and Drosophila growth promotion upon chronic undernutrition

The microbial environment influence animal physiology. However, the underlying molecular mechanisms of such functional interactions are largely undefined. Previously, we showed that upon chronic undernutrition, strains of Lactobacillus plantarum, a dominant commensal partner of Drosophila, promote host juvenile growth and maturation partly via enhanced expression of intestinal peptidases. By screening a transposon insertion library of Lactobacillus plantarum in gnotobiotic Drosophila larvae, we identify a bacterial cell wall modifying machinery encoded by the pbpX2-dltXABCD operon that is critical to enhance host digestive capabilities and promote growth and maturation. Deletion of this operon leads to bacterial cell wall alteration with a complete loss of teichoic acids D-alanylation. We thus conclude that teichoic acids modifications participate in commensal-host interactions and specifically, D-alanine esterification of teichoic acids contributes to optimal L. plantarum mediated intestinal peptidase expression and Drosophila juvenile growth upon chronic undernutrition.\n\nHighlights- LpNC8 mutant library screening identifies genes affecting Drosophila growth promotion.\n- pbpX2-dlt operon is required for D-alanylation of teichoic acids and Drosophila growth.\n- Deleting the pbpX2-dlt operon alters host intestinal peptidase expression.\n- Peptidoglycan and pbpX2-dlt dependent signals are required for LpNC8 mediated growth promotion.\n\n\neTOC blurbAnimals establish interactions with their microbial communities that shape many aspects of their physiology including juvenile growth. However, the underlying molecular mechanisms are largely undefined. Matos et al. reveal that bacterial teichoic acids modifications contribute to host juvenile growth promotion.

microbiology↗