HAL - RIIP
Not a member yet
17635 research outputs found
Sort by
The EPS-producing Paraburkholderia ultramafica: A tool for enhanced ecological restoration and metal bioremediation.
No full textInternational audiencePlant- associated bacteria are adapted to diverse environments, and most, known as plant growth- promoting rhizobacteria (PGPRs), have been shown to enhance plant growth and health, as well as increase resilience to biotic and abiotic stresses. Many PGPRs secrete mixtures of high- molecular- weight exopolysaccharides (EPSs) in response to physiological stress. EPSs have been shown to bind metals in soil, affecting the solubility of metal phosphates and, consequently, plant nutrition. Additionally, metal-resistant PGPRs can reduce metal stress in plants by decreasing the bioavailability of trace metals through complexation with their secreted EPSs. New Caledonia is a unique biodiversity hotspot, with one-third of the main island covered by ultramafic soils. These environments are exploited for ores such as Ni, Co, and Cr; therefore, sustainable and economically viable strategies are needed for ecological restoration and metal bioremediation.Paraburkholderia ultramafica STM 10279 T, a metal-tolerant rhizobacterium that promotes plant growth, was isolated from the roots of Tetraria arundinaceae, a pioneer endemic tropical herb growing on ultramafic soils in New Caledonia. We have reported that its metal tolerance is linked to the production of an acidic exopolysaccharide (EPS). To investigate the role of this EPS in environmental adaptation, we first elucidated its structure using a combination of chromatography and mass spectrometry techniques. It is a highly branched EPS composed of galactosyl (35. 8%), glucosyl (33. 2%), rhamnosyl (19. 5%), mannosyl (7. 7.2%), and glucuronosyl residues (4.4%). Subsequently, greenhouse experiments were conducted on Tetraria comosa plantlets inoculated with P. ultramafica or a solution of its EPS during transplanting onto ultramafic substrate. The results showed that the dry weight of T. comosa shoots was 2. 2.5 times higher in plants treated with the EPS compared to untreated plants. Analysis of plantlet composition revealed that exposure to the EPS significantly increased Ca, Mg, K, and P uptake, as well as K content and metal retention in roots. Furthermore, in vitro experiments using the Pikovskaya method demonstrated that the EPS could solubilize phosphorus. These findings indicate a beneficial effect of the rhizobacterial EPS on plant growth and metal stress reduction. Ongoing research seeks to see if this EPS can be developed as a biostimulant for promoting plant growth and adaptation to ultramafic soils. It could also be a useful tool in global bioremediation efforts to restore or clean up areas affected by mining activities
Biological screening of Xanthostemon and Myrtaceae essential oils from Oceania and of synthetic triketone analogues
No full textInternational audienc
Argonaute 2 targets viral transcripts but not genomes of RNA viruses during antiviral RNA interference in Drosophila
No full textInternational audienceRNA interference (RNAi) mediated by the small interfering RNA (siRNA) pathway is a major antiviral mechanism in insects. This pathway is triggered when double-stranded RNA (dsRNA) produced during virus replication is recognized by Dicer-2, leading to the formation of virus-derived siRNA duplexes. These siRNAs are loaded onto the programmable nuclease Argonaute-2 (AGO2), with one strand serving as a guide to target and cleave fully complementary sequences of viral RNAs. While siRNAs are generated from viral dsRNA, the specific viral RNA species targeted for silencing during RNA virus replication remains unclear. In this study, we characterized the primary viral RNA targets of the Drosophila siRNA pathway during infections caused by negative and positive RNA viruses, namely Vesicular stomatitis virus (VSV) and Sindbis virus (SINV). Our findings reveal that polyadenylated transcripts of VSV and SINV are the major targets of silencing by the siRNA pathway during infection, likely when they are poised for translation. Consistent with earlier findings, we show that AGO2 is associated with ribosomes in control and virus infected cells. Therefore, we propose that the inhibition of the replication of RNA viruses in Drosophila results from the silencing of incoming viral transcripts, facilitated by the association of AGO2 with ribosomes
Dysregulated proteostasis in p.A53T-α-Synuclein astrocytes aggravates Lewy-like neuropathology in a Parkinson’s disease iPSC model
No full textThe list of proteins detected in Ha samples at steady state is provided in Dataset S1. The list of differentially expressed proteins between PDa and Ha is provided in Dataset S2. Digital reconstructions of neuronal morphology have been submitted and are available at NeuroMorpho.Org. Source data on which the conclusions of the manuscript rely are available in Dataset S3. All study data are included in the article and/or supporting information.International audienceAlpha-Synuclein (αSyn) plays a central role in Parkinson’s disease (PD), and the p.A53T mutation causes an early-onset familial form of PD with severe manifestations. While its effects on neurons are well studied, its consequences on astrocytes and astrocytic contribution to PD pathology are understudied. Here, we differentiated patient-derived p.A53T-αSyn induced pluripotent stem cells (iPSC) to ventral midbrain astrocytes and characterized them via comprehensive molecular, functional, and proteomic analyses. Gene-corrected and healthy iPSC-derived astrocytes served as controls. To assess the effects of p.A53T-αSyn astrocytes on dopamine neurons, we established neuron–astrocyte cocultures of iPSC-derived control and mutant cells at all combinations. Our analyses uncovered cell-intrinsic pathologies in p.A53T-αSyn astrocytes, such as calcium dyshomeostasis, and accumulation of protein aggregates including those of phosphorylated αSyn. Proteomic and mechanistic studies demonstrated perturbed protein catabolic processes, with associated disturbances in lysosomal function and mTOR signaling. These deficits reduced the endocytic clearance capacity of p.A53T-αSyn astrocytes and their ability to process exogenous αSyn cargo. p.A53T-αSyn dopamine neurons cocultured with p.A53T-αSyn astrocytes displayed Lewy-like pathologies, mirroring the histopathological hallmarks identified in postmortem PD brains and exacerbated neurodegeneration, in anatomical and functional aspects. Control astrocytes mitigated these pathologies, highlighting their neuroprotective role. Additionally, p.A53T-αSyn astrocytes induced PD-relevant pathology ιn control neurons. Our findings, validated using an isogenic pair, demonstrate a critical impact of p.A53T-αSyn in disrupting astrocytic protein quality control mechanisms and establish astrocytes as active contributors to PD neuropathology. Our two-dimensional coculture model reflects key aspects of PD pathology, offering a relevant platform for mechanistic and drug discovery studies
Simultaneous Visualization of Distinct Posttranslational Modification States of β‐Catenin Using Genetic Code Expansion and Click Chemistry
No full textInternational audienceA novel strategy based on genetic code expansion combined with click chemistry for the simultaneous visualization of distinct posttranslational modification (PTM) states of a single protein within living cells. As a model, it is focused on threonine 41 (T41) of β-catenin, a regulatory hotspot implicated in epithelial cancers and known to be phosphorylated, O-GlcNAcylated, or left unmodified. Using site-specific incorporation of the unnatural phenylselenocysteine, a β-catenin-EGFP fusion protein is engineered allowing selective installation of a S-GlcNAc moiety via oxidative elimination and thiol-Michael ligation. Additional β-catenin variants, phosphomimetic T41E-mCherry and wild-type-blue fluorescent protein fusions, are produced to represent other PTM states. All constructs are successfully introduced into Hep3B and HeLa cells by lipofection or TAT-mediated transduction. Fluorescence microscopy revealed distinct subcellular localization profiles for each PTM form. Notably, the S-GlcNAcylated β-catenin exhibited enhanced resistance to proteasomal degradation, consistent with known roles of O-GlcNAcylation in protein stability. This approach provides a versatile platform to functionally probe PTMs in a comparative, cell-based context.</div
Opinion and report of the French Agency for Food, Environmental and Occupational Health and Safety (ANSES) relating to an analysis of the health risks associated with exposure to caterpillars with stinging hairs and the development of management recommendations
No full textXavier Bailly et Elsa Jourdain ne sont pas auteurs mais relecteurs du rapportInternational audienceSeveral species of Lepidoptera with caterpillars bearing urticating hairs are increasing their range in metropolitan France from year to year, such as the pine processionary (Thaumetopoea pityocampa Denis et Schiffermüller 1775) whose presence was historically limited to the south of France, and which is gradually being observed in the north and at higher altitudes. The procession period also seems to be appearing earlier. Climate change could have an impact on the range and phenology of this species, as well as other species of Lepidoptera with caterpillar bearing urticating hairs. Urticating caterpillars, which can trigger diffuse urticariform papules and allergic reactions for human people through contact with the skin, mucous membranes or inhalation, represent a health issue. These caterpillars also cause a health risk for animals and can have an impact on plants due to the resulting defoliation. This risk assessment therefore focused on the risk posed by these urticating caterpillars in areas where they have been established for a long time as well as in areas where they currently do not occur but could be colonized in the short or medium terms. One of the outputs of the evaluation consisted in identifying 55 different species of Lepidoptera with urticating caterpillars, for metropolitan France, but also for the overseas regions, based on the review by Kawamoto and Kumada (1984) and the GBIF database. In addition, detailed sheets for the well‐known species were drawn up, describing in particular their range, their phenology and the period when the urticating stages occur. A literature review as well as data from poison control centres and the analysis of the results of two surveys (of three associations of dermatologists/allergists and of occupational populations at risk) allowed to characterize the contexts of exposure and the human populations at risk. Concerning animal health, in addition to an epidemioclinical description based on the literature, data from veterinary poison control centres were analyzed in the specific case of dog exposure to the pine processionary between 1999 and 2021 in metropolitan french territory. Given the impact of these species of Lepidoptera on ecosystems, due to the defoliation they induce, this scientific opinion investigated the impact of these species on ecosystem services. The socio‐economic impacts of defoliations and risk management measures implemented in the event of an outbreak were studied based on a literature review and simulations for forest recreation. To represent risk for the whole metropolitan France territory, three risk maps of the human population exposure to the pine processionary, the oak processionary and the brown‐tail moth were designed at municipality level. A multi‐criteria analysis was undertaken to characterize danger (urticating caterpillars) and vulnerability of human populations. Then, the municipalities were ranked according to their level of danger and vulnerability. As a result, municipalities have been classified into 5 danger classes and 5 vulnerability classes. Based on a risk matrix with levels of hazard (abscissa axis) and levels of vulnerability (ordinate axis), 5 levels of risk were finally defined and the 34,816 municipalities of metropolitan France were classified according to their level of risk
Chikungunya virus replicates in the human testis ex vivo and impacts peritubular myoid cells functional markers
No full textInternational audienceChikungunya virus (CHIKV) is an emerging, mosquito-borne alphavirus responsible for debilitating, long-lasting arthralgia and myalgia. In light of recent findings of prolonged CHIKV RNA shedding in human semen and testicular tropism in animals infected with related alphaviruses, it is imperative to investigate CHIKV's capacity to infect the human testis, an established reservoir for arboviruses like Zika, and to delineate its implications for testicular function. Using an ex vivo human testicular tissue model, we demonstrate that CHIKV rapidly infects peritubular myoid cells (PMCs) and a range of interstitial cells, with robust viral production peaking at day 3 before declining. Importantly, seminiferous tubule cells and isolated testicular germ cells proved nonpermissive to CHIKV infection, indicating a potential limitation for seminal shedding of virions. Infected testicular explants exhibited a broad antiviral response but limited pro-inflammatory cytokines upregulation. CHIKV replication in the testis induced apoptosis and cell death, with a marked impact on PMC markers including decreased transcriptional expression of genes crucial for PMC contractile properties and extracellular matrix production. In summary, our study highlights the susceptibility of human testicular tissue to CHIKV infection, marked by robust viral replication that primarily compromises PMC function. The observed cellular impairment and damage suggest that CHIKV infection might negatively affect key testicular functions, such as tubular contractility and sperm release. These findings warrant further investigation into semen parameters and viral shedding in CHIKV-infected men
Bridging laboratory and field research: method adjustments to manipulate field-derived Aedes aegypti
No full textReference strains of Aedes aegypti , reared over numerous generations under laboratory conditions, are selected to fit laboratory conditions and commonly used in research due to their consistency and ease of handling. However, working exclusively with such strains may not fully reflect the traits of natural populations. While working on such strains is relevant in terms of reproducibility between labs, it is also important to perform some work on field-collected mosquitoes and their progeny to capture more representative biological and behavioural variation. In this study, we used the New Orleans reference strain as a control to adjust and evaluate methods to manipulate the F1 progeny of field-collected mosquitoes from Cayenne (French Guiana). To improve blood feeding rate, we tested the impact of several blood feeding systems for mosquitoes kept in a cage or in individual vials and adjusted starvation time. To monitor fertilization, we assessed if dissection buffer affects burst of spermatheca during dissection, whether mosquitoes were collected alive of shortly after death. The results described here may be helpful for studies on mosquito fitness, particularly on field-derived mosquitoes or on experiments requiring individual level monitoring. Author summary Aedes aegypti is the major vector of dengue virus, causing hundreds of millions of cases per year. To fight against disease transmission, mosquitoes are studied in the laboratory, notably using colonies of mosquitoes kept over decades in the laboratory. These reference strains have been selected to fit laboratory conditions and may thus not fully reflect the traits of natural populations. While working on such strains is relevant in a sake of consistency between labs and ease of handling, it is also important to work on field-collected mosquitoes and their progeny to capture more representative biological and behavioural variation. In this study, we adjusted and evaluated methods to manipulate the F1 progeny of field-collected mosquitoes from Cayenne (French Guiana), using the New Orleans reference strain as a control. To improve blood feeding rate, we tested the impact of several blood feeding systems for mosquitoes kept in a cage or in individual vials and adjusted starvation time. To monitor fertilization, we assessed if dissection buffer affects burst of spermatheca during dissection, whether mosquitoes were collected alive of shortly after death. The results described here may be helpful for studies on mosquito fitness, particularly on field-derived mosquitoes or on experiments requiring individual level monitoring
Polygenic viral factors enable efficient mosquito-borne transmission of African Zika virus
No full textPosted January 24, 2025 on bioRxiv.International audienceZika virus (ZIKV) is a mosquito-borne flavivirus primarily transmitted among humans by Aedes aegypti . Over the past two decades, it has caused significant outbreaks associated with birth defects and neurological disorders. Phylogenetically, ZIKV consists of two main genotypes referred to as the African and Asian lineages, each exhibiting distinct biological properties. African lineage strains are transmitted more efficiently by mosquitoes, but pinpointing the genetic basis of this difference has remained challenging. Here, we address this question by comparing recent African and Asian strains using chimeric viruses, in which segments of the parental genomes are swapped. Our results show that the structural genes from the African strain enhance viral internalization, while the non-structural genes improve genome replication and infectious particle production in mosquito cells. In vivo mosquito transmission is most significantly influenced by the structural genes, although no single viral gene alone determines this effect. Additionally, we develop a stochastic model of in vivo viral dynamics in mosquitoes that mirrors the observed patterns, suggesting that the primary difference between the African and Asian strains lies in their ability to traverse the mosquito salivary glands. Overall, our findings suggest that the polygenic nature of ZIKV transmissibility has prevented Asian lineage strains from achieving the same epidemic potential as African lineage strains, underscoring the importance of lineage-specific adaptive landscapes in shaping ZIKV evolution and emergence