Biology subjects

Lagorce, A.

Publications and source records attributed to Lagorce, A..

3 recordsLinked to original sources

bioRxiv2025

Multi-Omics Reprogramming Drives a Counterintuitive Reversal of Disease Susceptibility During Ageing

Ageing is a progressive and irreversible biological process characterized by the deterioration of physiological functions and increased vulnerability to mortality. Although extensively studied in vertebrates, ageing in long-lived invertebrates remains comparatively unexplored. While ageing typically leads to greater susceptibility to infectious diseases, a striking and unexpected reversal was identified in oysters: older oysters exhibit markedly increased tolerance to the Pacific Oyster Mortality Syndrome (POMS), a panzootic disease primarily driven by the OsHV-1 herpesvirus and responsible for severe losses in global aquaculture. To investigate this counterintuitive pattern, we challenged oysters aged 4, 16, and 28 months from four biparental families and conducted an integrative multi-omics analysis, including epigenomics, transcriptomics, and metabolomics on the two families showing the strongest age-related increase in survival. Our results reveal that ageing in Magallana gigas is characterized by coordinated epigenetic, transcriptional, and metabolic reprogramming that reduces host permissiveness to POMS. We show that the epigenetic remodeling of key immune regulators (e.g., Toll-like receptors, MyD88) aligns with transcriptional rewiring of NF-{kappa}B and ubiquitin pathways, producing a finely tuned innate immune state marked by enhanced antiviral activity but reduced antibacterial responsiveness. We also identify age-related repression of mTOR signaling, likely promoting autophagy and improving viral control. These regulatory changes are tightly linked to metabolic adjustments, including reduced TCA cycle flux, remodeled nitrogen metabolism, and altered glutathione dynamics, which collectively support a stress-tolerant, energy-conserving phenotype. Together, our findings reveal a fundamental evolutionary trade-off: juveniles prioritize growth at the cost of viral susceptibility, whereas adults invest in cellular maintenance and antiviral preparedness.

genomics↗

bioRxiv2025

Starvation of the bacteria Vibrio atlanticus promotes lightning group-attacks on the dinoflagellate Alexandrium pacificum

Phytoplankton serve as a source of nutrients for bacteria in the marine environment. The interactions between algae and bacteria are known to include mutualism, commensalism, competition or antagonism. This occurs in the microenvironment surrounding phytoplankton cells, the phycosphere, an interface rich in nutrients and organic molecules exuded by the cell. Here, based on in situ observations and on an in vitro interaction study, we report on a novel form of starvation-induced hunting that the cells of selected Vibrio species exert on dinoflagellates. The results showed that Vibrio atlanticus was capable of attacking and killing the dinoflagellate Alexandrium pacificum ACT03. Briefly, the observed mechanism of algal-killing consists of first, the immobilization stage involving the secretion of algicidal metabolites that disrupt the flagella of the algae. In the attack stage, Vibrios simultaneously surround algal cells at high density for a brief period without invading them. Finally, the killing stage in which the lysis and consumption of the dinoflagellates occur. By using a combination of biochemical, proteomic, molecular and fluorescence microscopy approaches, we showed that this relationship is not related to the decomposition of algal organic matter, Vibrio quorum sensing pathways, toxicity of the algae or pathogenicity of the bacterium but is conditioned by nutrient stress, iron availability and linked to the iron-vibrioferrin transport system of Vibrio atlanticus. This is the first evidence of a new mechanism that could be involved in regulating Alexandrium spp. blooms and giving Vibrio a competitive advantage in obtaining nutrients from the environment. The interaction model we propose here suggests that Vibrio could play a role in regulating the proliferation of Alexandrium spp., giving it a competitive advantage in obtaining nutrients from the environment.

microbiology↗

bioRxiv2023

Cooperation and cheating orchestrate Vibrio assemblages and polymicrobial synergy in oysters infected with OsHV-1 virus

Polymicrobial diseases significantly impact the health of humans and animals but remain understudied in natural systems. We recently described the Pacific Oyster Mortality Syndrome (POMS), a polymicrobial disease that impacts oyster production and is prevalent worldwide. Analysis of POMS-infected oysters on the French North Atlantic coast revealed that the disease involves co-infection with the endemic ostreid herpesvirus 1 (OsHV-1) and virulent bacterial species such as Vibrio crassostreae. However, it is unknown whether consistent Vibrio populations are associated with POMS in different regions, how Vibrio contribute to POMS, and how they interact with the OsHV-1 virus during pathogenesis. We resolved the Vibrio population structure in oysters from a Mediterranean ecosystem and investigated their functions in POMS development. We find that Vibrio harveyi and Vibrio rotiferianus are the predominant species found in OsHV-1-diseased oysters and show that OsHV-1 is necessary to reproduce the partition of the Vibrio community observed in the field. By characterizing the interspecific interactions between OsHV-1, V. harveyi and V. rotiferianus, we find that only V. harveyi synergizes with OsHV-1. When co-infected, OsHV-1 and V. harveyi behave cooperatively by promoting mutual growth and accelerating oyster death. V. harveyi showed high virulence potential in oysters and dampened host cellular defenses, making oysters a more favorable niche for microbe colonization. We next investigated the interactions underlying the co-occurrence of diverse Vibrio species in diseased oysters. We found that V. harveyi harbors genes responsible for the biosynthesis and uptake of a key siderophore called vibrioferrin. This important resource promotes the growth of V. rotiferianus, a cheater that efficiently colonizes oysters during POMS without costly investment in host manipulation nor metabolite sharing. By connecting field-based approaches, laboratory infection assays and functional genomics, we have uncovered a web of interdependencies that shape the structure and function of the POMS pathobiota. We showed that cooperative behaviors contribute to synergy between bacterial and viral co-infecting partners. Additional cheating behaviors further shape the polymicrobial consortium. Controlling such behaviors or countering their effects opens new avenues for mitigating polymicrobial diseases.

microbiology↗