Biology subjects

Moreau, S.

Publications and source records attributed to Moreau, S..

9 recordsLinked to original sources

bioRxiv2026

Anthropogenic-driven loss of an adaptive radiation reduces thermal response diversity

Biodiversity is predicted to stabilize ecosystems if species have different environmental responses. How this response diversity is shaped by ecological and evolutionary processes remains poorly understood. We determine the drivers of thermal response diversity of 16 Swiss peri-alpine lake-fish communities. We report the first evidence that evolutionary diversification of lineages through adaptive radiation can increase the response diversity of an ecosystem. In-situ diversification increases response diversity in the cold-deep lake environment, but non-endemic and non-native species contributed only weakly to response diversity. The loss of endemic species during historical anthropogenic eutrophication led to a negative legacy on present thermal response diversity in cold and deep lake strata. Overall, the interplay of evolutionary diversification, ecological assembly and anthropogenic impacts drives variation in response diversity. Conserving and restoring processes that generate diversity may help maintain ecosystem stability beyond the Anthropocene.

ecology↗

bioRxiv2026

A fatal plant toxicosis described more than a century ago is caused by a bacterial endophyte

Gousiekte ( quick disease) is a fatal plant toxicosis affecting livestock in South Africa. Gousiekte is characterized by the sudden death of animals following the ingestion of leaves of several species of Rubiaceae, most notably Vangueria pygmaea, Pavetta harborii, P. schumanniana and Fadogia homblei. The toxin causing gousiekte is pavettamine, a hydroxylated polyamine pavettamine for which no biosynthetic pathway is known. Interestingly, all plants known to contain pavettamine also feature obligate endophytes of the Burkholderiaceae family, in particular belonging to the Caballeronia and Paraburkholderia genera. We identified a cluster of three genes conserved in all Burkholderia s.l. endophytic symbionts of plants containing pavettamine. Constitutive expression the pavABC gene cluster in a strain of Paraburkholderia caledonica isolated from leaves of Fadogia homblei resulted in detectable levels of pavettamine in cultures, and targeted gene deletions showed the involvement of all three genes in its biosynthesis. Genomes of important animal and human pathogens of the Burkholderia pseudomallei complex encode functional homologs of the pavABC genes, indicating a potentially unrecognized role of pavettamine in disease or complications from infections. Significance statementGousiekte is a fatal disease of livestock caused by plants containing the toxin pavettamine, yet the origin of this compound has remained a mystery. We demonstrate that pavettamine is synthesized not by the plants themselves, but by their obligate bacterial endophytes via a conserved three-gene cluster, pavABC. Crucially, these genes were likely acquired via horizontal gene transfer from an ancestor of the Burkholderia pseudomallei complex, a group of significant human and animal pathogens. This discovery identifies the genetic basis of a potent toxin and suggests a previously unrecognized role for pavettamine in human infectious diseases. This work emphasizes the preeminent role of horizontal gene transfer and secondary metabolism for host-microbe interactions.

microbiology↗

bioRxiv2026

A plant single nucleotide polymorphism impacts nectar sugar composition, microbial diversity and pollinator visits

Nectar is a hub for plant-pollinator interactions, yet gene-level causal links between plant genetic variation, pollinator foraging and nectar microbial assembly remain poorly resolved. Using near-isogenic lines, innovative field time-lapse monitoring of pollinator visits and long-read amplicon sequencing of nectar microbiota, we show that a natural single-nucleotide variant at a cell-wall invertase gene (HaCWINV2) controls sunflower nectar chemistry and influences both pollinators and microbes. Plants homozygous for a loss-of-function HaCWINV2 allele produce sucrose-rich nectar, resulting in fewer bee visits under field conditions, while bumblebee visitation remained unaffected. In pollinator-excluded flowers, invertase-deficient plants harboured greater fungal diversity and compositionally distinct communities, indicating that nectar sugar profiles act as ecological filters shaping the nectar microbiome. This loss-of-function allele was found rarely and only at the heterozygote state in wild sunflowers and was fixed in 35% of cultivated lines indicating a positive selection during domestication. Our findings establish a causal link between a single gene and nectar chemistry with cascading ecological effects in a plant-pollinator system, illustrating how subtle genetic changes scale up to alter nectar traits, microbial assembly and pollinator foraging behaviour.

genetics↗

bioRxiv2025

Learn to hear your prey: The role of associative learning on web building and hunting behaviour in black widow spiders (Latrodectus hesperus)

Individuals from many populations vary consistently in their diet or behaviour. Associative learning could lead to such specialisation by improving the ability of predators to detect or recognize prey types or optimizing the sensory cues or spatial locations that they attend to. In this study, we assess the ability of Western black widow spiders for associative learning in response to vibrational prey cues. Black widow spiders are sedentary predators that detect, identify, and choose whether to attack preys caught in the web using the frequency and strength of vibrations. We conducted two experiments assessing the ability of individuals to associate specific frequencies or spatial locations on the web to the presence of a prey. We analyzed changes in web structure and attack behavior through learning. We hypothesized that individuals would adjust the structure of their webs and their responsiveness towards these frequencies in response to these associations. Spiders did not adjust the structure of their web nor their response to specific web locations when we applied prey items and vibrations at specific locations on the web. Instead, all spiders increased their responsiveness to vibrations at 250 Hz irrespective of their experimental treatment, but not towards 25Hz cues. Unexpectedly, exposing spiders to prey items associated with a 250Hz increased the effect of trap threads on responsiveness itself. Hence, repeated exposures, even when paired with food on rare occasions can alter foraging behavior in this species. Individuals could adjust their foraging behavior by tending more or less intensely to specific sensory information. This generalist predator could change major components of its foraging behavior through learning, but the effect of learning on behavior appears mediated by web structure. Learning combined with variation in web structure could explain the substantial individual differences in attack behavior we observe in this species.

ecology↗

bioRxiv2025

Artificial symbiont replacement in a vertically-transmitted plant-bacterium association provides insights into the basis for specificity

Some plants engage in permanent, vertically transmitted symbioses with bacteria. Often, these bacteria are hosted extracellularly in specific structures on the leaves, where they produce specialized bioactive metabolites that benefit their host. These associations are highly specific, with one plant species associating with a single bacterial species, but little is known about how these symbioses originate and how specificity is maintained. In this study, we show that the symbiotic association between a wild yam and a bacterium can be manipulated experimentally, and that bacteria-free plants are open to colonization by environmental bacteria. Through metabolic profiling, we show that the endophytic niche is rich in organic acids and intermediates of the TCA cycle. Environmental bacteria capable of utilizing these acids, such as the soil bacterium Pseudomonas putida, readily colonize aposymbiotic plants. However, successful colonization is contingent upon the absence of the vertically-transmitted symbiont and an active type VI secretion system. Unexpectedly for a vertically-transmitted symbiosis, these findings suggest that microbe-microbe interactions, including antagonism, may play a crucial role in maintaining the specificity of an association. However, low transmission rates of synthetic symbionts provide evidence that transmission barriers or bottlenecks may still occur, further enforcing partner fidelity. Together, these results highlight the complexity of mechanisms underlying mutualistic associations, and provide insights into the evolution of bacterial leaf symbiosis.

microbiology↗

bioRxiv2024

Reversible and reusable compartmentalized microfluidic chip for coculture of dorsal root ganglion neurons

Compartmentalized microfluidic chips play an important role in understanding the cellular mechanisms involved in neurodegenerative disorders. Dorsal root ganglia are a well-established model for modelling the peripheral nervous system (PNS), but their development on a chip remains limited. Furthermore, it would be beneficial for the devices to be openable in order to access the biological material inside for analyses. Easy to prototype and biocompatible, styrenic block copolymers (SBC) are an alternative to polydimethylsiloxane (PDMS) that offer both reversible and permanent bonding properties. This paper presents a fast and straightforward method to produce compartmentalized SBC chips. The study validates the culture of murine dorsal root ganglia explants, comparing it to the standard methods, to obtain a model of the PNS. Moreover, the reversible bonding properties of the SBC permit the reuse of the chip with a quick and easy cleaning protocol. It provides direct access to the cells, opening the way for imaging and molecular biology analysis. The comparison of the resources required to produce PDMS and SBC chips highlights the importance of moving to reusable devices. These detachable, easy-to-manufacture and sustainable all-thermoplastic platforms provide an alternative way of prototyping compartmentalized devices for in vitro PNS modeling.

biophysics↗

bioRxiv2023

The association between Dioscorea sansibarensis and Orrella dioscoreae as a model for hereditary leaf symbiosis

Hereditary, or vertically-transmitted, symbioses affect a large number of animal species and some plants. The precise mechanisms underlying transmission of functions of these associations are often difficult to describe, due to the difficulty in separating the symbiotic partners. This is especially the case for plant-bacteria hereditary symbioses, which lack experimentally tractable model systems. Here, we demonstrate the potential of the leaf symbiosis between the wild yam Dioscorea sansibarensis and the bacterium Orrella dioscoreae (O. dioscoreae) as a model system for hereditary symbiosis. O. dioscoreae is easy to grow and genetically manipulate, which is unusual for hereditary symbionts. These properties allowed us to design an effective antimicrobial treatment to rid plants of bacteria and generate whole aposymbiotic plants, which can later be re-inoculated with bacterial cultures. Aposymbiotic plants did not differ morphologically from symbiotic plants and the leaf forerunner tip containing the symbiotic glands formed normally even in the absence of bacteria, but microscopic differences between symbiotic and aposymbiotic glands highlight the influence of bacteria on the development of trichomes and secretion of mucilage. This is to our knowledge the first leaf symbiosis where both host and symbiont can be grown separately and where the symbiont can be genetically altered and reintroduced to the host.

plant biology↗

bioRxiv2021

Distinct within-host bacterial populations ensure function, colonization and transmission in leaf symbiosis

Hereditary symbioses have the potential to drive transgenerational effects, yet the mechanisms responsible for transmission of heritable plant symbionts are still poorly understood. The leaf symbiosis between Dioscorea sansibarensis and the bacterium Orrella dioscoreae offers an appealing model system to study how heritable bacteria are transmitted to the next generation. Here, we demonstrate that inoculation of apical buds with a bacterial suspension is sufficient to colonize newly-formed leaves and propagules, and to ensure transmission to the next plant generation. Flagellar motility is not required for movement inside the plant, but is important for the colonization of new hosts. Further, stringent tissue-specific regulation of putative symbiotic functions highlight the presence of two distinct subpopulations of bacteria in the leaf gland and at the shoot meristem. We propose that bacteria in the leaf gland dedicate resources to symbiotic functions, while dividing bacteria in the shoot tip ensure successful colonization of meristematic tissue, glands and propagules. Compartmentalization of intra-host populations, together with tissue-specific regulation may serve as a robust mechanism for the maintenance of mutualism in leaf symbiosis. ImportanceSeveral plant species form associations with bacteria in their leaves, called leaf symbiosis. These associations are highly specific, but the mechanisms responsible for symbiont transmission are poorly understood. Using the association between the yam species Dioscorea sansibarensis and Orrella dioscoreae as a model leaf symbiosis, we provide experimental evidence that bacteria are transmitted vertically and distributed to specific leaf structures via association with shoot meristems. Flagellar motility is required for initial infection, but does not contribute to spread within host tissue. We also provide evidence that bacterial subpopulations at the meristem or in the symbiotic leaf gland differentially express key symbiotic genes. We argue that this separation of functional symbiont populations, coupled to tight control over bacterial infection and transmission, explain the evolutionary robustness of leaf symbiosis. These findings may provide insights into how plants may recruit and maintain beneficial symbionts at the leaf surface.

microbiology↗

bioRxiv2020

Chromosomal resolution reveals symbiotic virus colonization of parasitic wasp genomes

Most endogenous viruses, an important proportion of eukaryote genomes, are doomed to slowly decay. Little is known, however, on how they evolve when they confer a benefit to their host. Bracoviruses are essential for the parasitism success of parasitoid wasps, whose genomes they integrated ~103 million years ago. Here we show, from the assembly of a parasitoid wasp genome, for the first time at a chromosomal scale, that symbiotic bracovirus genes spread to and colonized all the chromosomes. Moreover, large viral clusters are stably maintained suggesting strong evolutionary constraints. Genomic comparison with another wasps revealed that this organization was already established ~53 mya. Transcriptomic analyses highlight temporal synchronization of viral gene expression, leading to particle production. Immune genes are not induced, however, indicating the virus is not perceived as foreign by the wasp. This recognition suggests that no conflicts remain between symbiotic partners when benefits to them converge.

genomics↗