Biology subjects

Bastien, M.

Publications and source records attributed to Bastien, M..

5 recordsLinked to original sources

bioRxiv2026

Asymptomatic colonization by Botrytis cinerea reveals polarized plant-fungus interfaces before widespread disease

Botrytis cinerea is a necrotrophic pathogen whose destructive growth is typically studied under conditions that rapidly generate visible disease. Yet symptomless associations are well documented, the fungal and host processes operating before widespread tissue collapse remain poorly resolved. We developped an intact Arabidopsis thaliana seedling pathosystem that extends the interval between infection establishment and widespread visible disease. Fungal colonization was quantified using qPCR and a constitutively bioluminescent reporter strain, together with longitudinal plant phenotyping, hormone profiling and multiscale fluorescence microscopy. Substantial fungal colonization occurred while seedlings remained largely green and continued to grow, whereas robust whole seedling accumulation of salicylic and jasmonic acids occurred later. During this interval, B. cinerea displayed diverse tissue-associated infection morphologies. At individual contact sites, fungal walls showed heterogeneous exposure of chitin-associated epitopes, while host cells exhibited focal plasma-membrane polarization toward fungal contact sites, together with cortical actin reorganization. These results show that the interval preceding widespread visible disease is an active and spatially heterogeneous interaction state, in which substantial fungal development and highly organized local host responses are already established. Intact seedlings therefore provide a powerful system for resolving plant-pathogen interactions that are largely obscured in rapid disease assays.

pathology↗

bioRxiv2025

First detection of Crimean Congo Hemorrhagic Fever antibodies in cattle and wild fauna of southern continental France: investigation of explicative factors

Crimean-Congo Haemorrhagic Fever (CCHF) is a tick-borne zoonosis with significant public health implications due to its expanding geographic distribution and potential for severe outcomes in humans. This study represents the first serological survey conducted in mainland France to detect antibodies against the Crimean-Congo Haemorrhagic Fever Virus (CCHFV) in domestic and wild fauna, providing critical insights into the viruss circulation. We analyzed 8,609 cattle sera and 2,182 wildlife sera collected across the French Mediterranean region from 2008 to 2022, using enzyme-linked immunosorbent assays (ELISA) and pseudo-plaque reduction neutralization tests (PPRNT) for antibody detection and confirmation. Seropositivity was detected in both cattle (2.04%) and wildlife (2.25%), with higher rates observed in specific regions such as Pyrenees-Orientales and Hautes-Pyrenees. These findings reveal spatial clusters of CCHFV circulation and suggest the existence of enzootic transmission cycles involving local tick vectors and animal hosts. Our multivariate analysis identified key factors influencing seropositivity, including animal age, habitat characteristics, and potential wildlife interactions. The presence of natural open habitats and coniferous forests was significantly associated with higher seropositivity in cattle, while sex and geographical variability played a role in wildlife seroprevalence. These findings highlight the importance of environmental and anthropogenic factors in shaping the dynamics of CCHFV transmission. This study demonstrates that CCHFV is actively circulating in parts of mainland France, emphasizing the need for enhanced surveillance and integrated approaches to monitor zoonotic pathogens. It also raises questions about the role of additional tick vectors, such as Hyalomma lusitanicum, in the transmission cycle. These results contribute to a better understanding of CCHF epidemiology and offer valuable guidance for public health strategies to mitigate the risks associated with this emerging disease. Author SummaryCrimean-Congo Haemorrhagic Fever (CCHF) is a severe disease spread by ticks that affects humans and animals. Although the disease is largely distributed in parts of Europe, Africa, and Asia, its presence in France has been uncertain. My study investigated whether the virus causing this disease is circulating in southern mainland France by testing blood samples from domestic animals, like cattle, and wild animals, such as deer and wild boars, for signs of previous infection. I found evidence of the virus in several regions, particularly in the Pyrenees-Orientales, Hautes-Pyrenees and Alpes-maritimes, suggesting that the virus is indeed circulating among animals and ticks in some parts of mainland France. By studying where infected animals were found and considering factors such as age, habitat, and environmental conditions, I identified that older animals seem to have been more often exposed to the virus, as well as animals frequenting open environments favorable to ticks. These findings are important because they show that the disease could potentially spread to new areas and affect human populations. My work highlights the need for ongoing monitoring of ticks and animals for CCHFV epidemiological surveillance and the protection of public health.

ecology↗

bioRxiv2025

Spatial pattern of serology against Borrelia and tick-borne encephalitis virus in roe deer (Capreolus capreolus), Northern France, 2019-2022

BackgroundLyme borreliosis and tick-borne encephalitis (TBE) are tick-borne zoonoses of public health importance, transmitted in Western Europe by the same tick vector Ixodes ricinus. Roe deer (Capreolus capreolus) is a widespread feeding host for I. ricinus stages. Here, we explored the spatial extent of both pathogens in the wild in Northern France by assessing serological status in roe deer. MethodsWe collected 3,147 blood samples (2019-2022), and searched antibodies against both pathogens using ELISA tests. We fitted logistic models to investigate exposure to both or either pathogens, and explored spatial patterns using Kulldorf clustering scan tests. ResultsThe overall ELISA IgG prevalence was 23.24% (95%CI [21.77-34.72]) for Borrelia and 8.64% (95%CI [7.45-9.86]) for TBEV. The median Borrelia seroprevalence varied from 4% to 42% between departments, with two high-risk clusters of exposure identified. TBEV seroprevalence did not show any spatial pattern, and positives by seroneutralisation tests were reported in eight departments. DiscussionOur findings suggest the presence of both pathogens over large areas. Wider spatial sampling including areas at lower risk and improved serological methods would be beneficial to further validate those estimates.

ecology↗

bioRxiv2024

Tick-borne pathogens identified in Hyalomma marginatum (Acari: Ixodidae) collected from various vertebrate hosts in the South of France

Hyalomma marginatum is a common ectoparasitic tick of ungulates, lagomorphs, insectivores, ground-foraging birds, observed in Corsica for decades, but whose permanent establishment in mainland France is very recent. This species is known to be one of the main vectors of the Crimean-Congo Hemorrhagic Fever virus, but also of various parasitic, bacterial or viral pathogens. In this study, we investigated the molecular infection rates of numerous tick-borne pathogens in H. marginatum ticks mainly sampled on horses, and occasionally on other animal species, from the French Mediterranean rim and Corsica between 2016 and 2020. In total, 1, 195 DNA and RNA purified from individual ticks or pools of ticks were screened for 26 microbial genera or species (viruses, bacteria and parasites), using a high-throughput microfluidic real-time PCR system (BioMark dynamic array system, Standard Biotools). For individual ticks and pooled ones, respectively, the most prevalent tick-borne microorganisms were Francisella-like endosymbionts at 97.0% and 96.8%, followed by Rickettsia aeschlimannii (76.4% and 96.4%), Theileria spp. and Theileria equi (3,5% and 0%; 1,9% and 5,8%), Anaplasma phagocytophilum (3.7% and 6.7%), and West Nile virus (0.1% and 0.4%). Babesia occultans (0.9%), Ehrlichia minasensis (0.3%), and Coxiella-like endosymbionts (0.1%) were only detected in individual ticks. Our study provides an overview of the diversity of microorganisms and tick-borne pathogens detected in the invasive tick H. marginatum in Corsica and the continental departments of the Mediterranean rim. Our study opens up new research perspectives on the epidemiology of tick-borne pathogens carried by H. marginatum and on the associated public and veterinary health risks.

microbiology↗

bioRxiv2019

Intragenic recruitment of NF-κB drives alternative splicing modifications upon activation by the viral oncogene TAX of HTLV-1.

The chronic NF-{kappa}B activation in inflammation and cancer has long been linked to persistent activation of NF-{kappa}B responsive gene promoters. However, NF-{kappa}B factors such as RELA also massively bind to gene bodies. Here, we demonstrate that the recruitment of RELA to intragenic regions regulates alternative splicing upon activation of NF-{kappa}B by the viral oncogene TAX of HTLV-1. Integrative analysis of RNA splicing and chromatin occupancy, combined with chromatin tethering assays, demonstrate that DNA-bound RELA interacts with and recruits the splicing regulator DDX17 in a NF-kB activation-dependent manner, leading to alternative splicing of target exons thanks to DDX17 RNA helicase activity. This NF-kB/DDX17 axis accounts for a major part of the TAX-induced alternative splicing landscape that mainly affects genes involved in oncogenic pathways. Collectively, our results demonstrate a physical and direct involvement of NF-{kappa}B in alternative splicing regulation, which significantly revisits our knowledge of HTLV-1 pathogenesis and other NF-{kappa}B-related diseases.

molecular biology↗