Rapid and dfferential evolution of the venom composition of a parasitoid wasp depending on the host strain

Abstract: Parasitoid wasps rely primarily on venom to suppress the immune response and regulatethe physiology of their host. Intraspecific variability of venom protein composition has beendocumented in some species, but its evolutionary potential is poorly understood. We performed anexperimental evolution initiated with the crosses of two lines of Leptopilina boulardi of differentvenom composition to generate variability and create new combinations of venom factors. Theoffspring were maintained for 10 generations on two strains of Drosophila melanogaster differing inresistance/susceptibility to the parental parasitoid lines. The venom composition of individuals wascharacterized by a semi-automatic analysis of 1D SDS-PAGE electrophoresis protein profiles whoseaccuracy was checked by Western blot analysis of well-characterized venom proteins. Results madeevident a rapid and differential evolution of the venom composition on both hosts and showed thatthe proteins beneficial on one host can be costly on the other. Overall, we demonstrated the capacityof rapid evolution of the venom composition in parasitoid wasps, important regulators of arthropodpopulations, suggesting a potential for adaptation to new hosts. Our approach also proved relevantin identifying, among the diversity of venom proteins, those possibly involved in parasitism successand whose role deserves to be deepened

Variation in the Venom of Parasitic Wasps, Drift, or Selection? Insights From a Multivariate QST Analysis

Differentiation of traits among populations can evolve by drift when gene flow is low relative to drift or selection when there are different local optima in each population (heterogeneous selection), whereas homogeneous selection tends to prevent evolution of such a differentiation. Analyses of geographical variations in venom composition have been done in several taxa such as wasps, spiders, scorpions, cone snails and snakes, but surprisingly never in parasitoid wasps, although their venom should constrain their ability to succeed on locally available hosts. Such a study is now facilitated by the development of an accurate method (quantitative digital analysis) that allows analyzing the quantitative variation of large sets of proteins from several individuals. This method was used here to analyse the venom-based differentiation of four samples of Leptopilina boulardi and five samples of L. heterotoma from populations along a 300 km long south-north gradient in the Rhône-Saône valley (South-East of France). A major result is that the composition of the venom allows to differentiate the populations studied even when separated by few kilometers. We further analyzed these differentiations on the populations (reared under similar conditions to exclude environmental variance) with a QST analysis which compared the variance of a quantitative trait (Q) among the subpopulations (S) to the total variance (T). We also used random forest clustering analyses to detect the venom components the most likely to be adapted locally. The signature of the natural selection was strong for L. heterotoma and L. boulardi. For the latter, the comparison with the differentiation observed at some neutral markers revealed that differentiation was partly due to some local adaptation. The combination of methods used here appears to be a powerful framework for population proteomics and for the study of eco-evolutionary feedbacks between proteomic level and population and ecosystem levels. This is of interest not only for studying field evolution at an intermediate level between the genome and phenotypes, or for understanding the role of evolution in chemical ecology, but also for more applied issues in biological control

Insect population dynamics under Wolbachia -induced cytoplasmic incompatibility: puzzle more than buzz in Drosophila suzukii

Abstract Wolbachia pipientis is an intracellular bacterium that infects many insects and other arthropods. Cytoplasmic incompatibility (CI) is one of several effects that Wolbachia has on its hosts. In its simplest form, CI causes host reproductive failure when an uninfected female mates with an infected male. Theoretically, this has two consequences. First, when an incompatible Wolbachia strain is introduced into a recipient host population, uninfected females are selected against, triggering Wolbachia invasion. Second, reproductive failures during Wolbachia invasion lead to a transient decrease in population growth rate. Modelling studies combining Wolbachia invasion and host population dynamics show that these two processes could interact to cause population decline and even extinction. However, these effects could be sensitive to density dependence, with competition reducing the demographic impact of CI and Allee effect increasing the probability of extinction. We tested these predictions with laboratory experiments in the fruit fly Drosophila suzukii and the exogenous Wolbachia strain w Tei. Surprisingly, the introduction of w Tei into D. suzukii populations at carrying capacity did not result in the expected invasion of w Tei and transient population decline. In parallel, we found strong negative density dependence, but no Allee effect. From these results, we propose that negative density dependence is an important but underappreciated driver of the eco-evolutionary feedback underlying Wolbachia invasion and insect population dynamics. If future models and data support this hypothesis, pest management strategies using Wolbachia -induced CI should target early-season populations with negligible competition but a possible Allee effect

Processing and secretion of guanylate binding protein-1 depend on inflammatory caspase activity.

Human guanylate binding protein-1 (GBP-1) belongs to the family of large GTPases. The expression of GBP-1 is inducible by inflammatory cytokines, and the protein is involved in inflammatory processes and host defence against cellular pathogens. GBP-1 is the first GTPase which was described to be secreted by eukaryotic cells. Here, we report that precipitation of GBP-1 with GMP-agarose from cell culture supernatants co-purified a 47-kD fragment of GBP-1 (p47-GBP-1) in addition to the 67-kD full-length form. MALDI-TOF sequencing revealed that p47-GBP-1 corresponds to the C-terminal helical part of GBP-1 and lacks most of the globular GTPase domain. In silico analyses of protease target sites, together with cleavage experiments in vitro and in vivo, showed that p67-GBP-1 is cleaved by the inflammatory caspases 1 and 5, leading to the formation of p47-GBP-1. Furthermore, the secretion of p47-GBP-1 was found to occur via a non-classical secretion pathway and to be dependent on caspase-1 activity but independent of inflammasome activation. Finally, we showed that p47-GBP-1 represents the predominant form of secreted GBP-1, both in cell culture supernatants and, in vivo, in the cerebrospinal fluid of patients with bacterial meningitis, indicating that it may represent the biologically active form of extracellular GBP-1. These findings confirm the involvement of caspase-1 in non-classical secretion mechanisms and open novel perspectives for the extracellular function of secreted GBP-1

Field monitoring of <em>Drosophila suzukii</em> and associated communities in south eastern france as a Pre-requisite for classical biological control

International audienceThe spotted wing Drosophila, Drosophila suzukii (Ds), became a major economic pest for fruit production since its establishment in Europe and America. Among potential control methods, only classical biological control appears to be a mean of sustainably regulating Ds in both cultivated and natural habitats. In the frame of risk assessment, pre-release surveys were carried out in a restricted but highly heterogeneous area in the south-east of France using traps and deliberate field exposures of Ds and D. melanogaster larvae/pupae. Although Ds abundance varied according to sampling methods, it was found to be pervasive and to produce offspring and adults in most conditions (spatial and seasonal). Its main limits are some specific abiotic conditions (i.e., desiccation) as well as interspecific competition. Indeed, Ds mostly co-occurred with D. busckii and D. hydei, probably due to common phenology and/or ecological requirements. These two species thus deserve more attention for risk assessment. The main indigenous parasitoids collected belonged to two pupal species, Trichopria cf drosophilae and Pachycrepoideus vindemmiae, but their presence was observed late in the autumn and mainly in cultivated areas. Results are discussed in a comparison of the methodological approaches for monitoring Drosophilids and the benefits-risks assessment of classical biological control

Rapid and dfferential evolution of the venom composition of a parasitoid wasp depending on the host strain

Abstract: Parasitoid wasps rely primarily on venom to suppress the immune response and regulate the physiology of their host. Intraspecific variability of venom protein composition has been documented in some species, but its evolutionary potential is poorly understood. We performed an experimental evolution initiated with the crosses of two lines of Leptopilina boulardi of different venom composition to generate variability and create new combinations of venom factors. The offspring were maintained for 10 generations on two strains of Drosophila melanogaster differing in resistance/susceptibility to the parental parasitoid lines. The venom composition of individuals was characterized by a semi-automatic analysis of 1D SDS-PAGE electrophoresis protein profiles whose accuracy was checked by Western blot analysis of well-characterized venom proteins. Results made evident a rapid and differential evolution of the venom composition on both hosts and showed that the proteins beneficial on one host can be costly on the other. Overall, we demonstrated the capacity of rapid evolution of the venom composition in parasitoid wasps, important regulators of arthropod populations, suggesting a potential for adaptation to new hosts. Our approach also proved relevant in identifying, among the diversity of venom proteins, those possibly involved in parasitism success and whose role deserves to be deepened

Interplay between trauma and Pseudomonas entomophila infection in flies: a central role of the JNK pathway and of CrebA

International audienceIn mammals, both sterile wounding and infection induce inflammation and activate the innate immune system, and the combination of both challenges may lead to severe health defects, revealing the importance of the balance between the intensity and resolution of the inflammatory response for the organism's fitness. Underlying mechanisms remain however elusive. Using Drosophila, we show that, upon infection with the entomopathogenic bacterium Pseudomonas entomophila (Pe), a sterile wounding induces a reduced resistance and increased host mortality. To identify the molecular mechanisms underlying the susceptibility of wounded flies to bacterial infection, we analyzed the very first steps of the process by comparing the transcriptome landscape of infected (simple hit flies, SH), wounded and infected (double hit flies, DH) and wounded (control) flies. We observed that overexpressed genes in DH flies compared to SH ones are significantly enriched in genes related to stress, including members of the JNK pathway. We demonstrated that the JNK pathway plays a central role in the DH phenotype by manipulating the Jra/dJun activity. Moreover, the CrebA/Creb3‐like transcription factor (TF) and its targets were up‐regulated in SH flies and we show that CrebA is required for mounting an appropriate immune response. Drosophila thus appears as a relevant model to investigate interactions between trauma and infection and allows to unravel key pathways involved

Rapid and differential evolution of the venom composition of a parasitoid wasp depending on the host strain

Parasitoid wasps rely primarily on venom to suppress the immune response and regulate the physiology of their host. Intraspecific variability of venom protein composition has been documented in some species, but its evolutionary potential is poorly understood. We performed an experimental evolution initiated with crosses of two lines of Leptopilina boulardi of different venom composition to generate variability and create new combinations of venom factors. The offspring were maintained for 10 generations on two strains of Drosophila melanogaster differing in resistance / susceptibility to the parasitoid lines. The venom composition of individuals was characterized by a semi-automatic analysis of 1D SDS-PAGE protein profiles whose accuracy was checked by Western blot analysis of well-characterized venom proteins. Results evidenced a rapid and differential evolution of the venom composition on both hosts and showed that the proteins beneficial on one host can be costly on the other. Overall, we demonstrated the capacity of rapid evolution of the venom composition in parasitoid wasps, important regulators of arthropod populations, suggesting a potential for adaptation to new hosts. Our approach also proved relevant in identifying, among the diversity of venom proteins, those possibly involved in parasitism success and whose role deserves to be deepened

Genetic architecture of natural variations of cardiac performance in flies

Abstract Background Deciphering the genetic architecture of cardiac disorders is of fundamental importance but their underlying complexity is a major hurdle. Drosophila has gained importance as a useful model to study heart development and function and allows the analysis of organismal traits in a physiologically relevant and accessible system. Our aim was to (i) identify in flies the loci associated to natural variations of cardiac performances among a natural population, (ii) decipher how these variants interact with each other and with the environment to impact cardiac traits, (iii) gain insights about the molecular and cellular processes affected, (iv) determine whether the genetic architecture of cardiac disorders is conserved with humans. Methods and Results We investigated the genetic architecture of natural variations of cardiac performance in the sequenced inbred lines of the Drosophila Genetic Reference Panel (DGRP). Genome Wide Associations (GWA) for single markers and epistatic interactions identified genetic networks associated with natural variations of cardiac traits that were extensively validated in vivo. Non-coding variants were used to map potential regulatory non-coding regions which in turn were employed to predict Transcription Factors (TFs) binding sites. Cognate TFs, many of which themselves bear polymorphisms associated with variations of cardiac performance, were validated by heart specific knockdown. We also analyzed natural variations of cardiac traits variance that revealed unique features of their micro-environmental plasticity. More importantly, correlations between genes associated with cardiac phenotypes both in flies and in humans support the conserved genetic architecture of cardiac functioning from arthropods to mammals. The characteristics of natural variations in cardiac function established in Drosophila may thus guide the analysis of cardiac disorders in humans. Using human iPSC-derived cardiomyocytes, we indeed characterized a conserved function for PAX9 and EGR2 in the regulation of the cardiac rhythm Conclusion In-depth analysis of the genetic architecture of natural variations of cardiac performance in flies combined with functional validations in vivo and in human iPSC-CM represents a major achievement in understanding the mechanisms underlying the genetic architecture of these complex traits and a valuable resource for the identification of genes and mechanisms involved in cardiac disorders in humans

Genetic architecture of natural variation of cardiac performance from flies to humans

Deciphering the genetic architecture of human cardiac disorders is of fundamental importance but their underlying complexity is a major hurdle. We investigated the natural variation of cardiac performance in the sequenced inbred lines of the Drosophila Genetic Reference Panel (DGRP). Genome-wide associations studies (GWAS) identified genetic networks associated with natural variation of cardiac traits which were used to gain insights as to the molecular and cellular processes affected. Non-coding variants that we identified were used to map potential regulatory non-coding regions, which in turn were employed to predict transcription factors (TFs) binding sites. Cognate TFs, many of which themselves bear polymorphisms associated with variations of cardiac performance, were also validated by heart-specific knockdown. Additionally, we showed that the natural variations associated with variability in cardiac performance affect a set of genes overlapping those associated with average traits but through different variants in the same genes. Furthermore, we showed that phenotypic variability was also associated with natural variation of gene regulatory networks. More importantly, we documented correlations between genes associated with cardiac phenotypes in both flies and humans, which supports a conserved genetic architecture regulating adult cardiac function from arthropods to mammals. Specifically, roles for PAX9 and EGR2 in the regulation of the cardiac rhythm were established in both models, illustrating that the characteristics of natural variations in cardiac function identified in Drosophila can accelerate discovery in humans