Biology subjects

Meunier, F.

Publications and source records attributed to Meunier, F..

15 recordsLinked to original sources

bioRxiv2026

Long-term liana infestation leaves architectural legacies in host trees

Lianas are an integral component of tropical forests, and their increasing abundance may alter forest structure and function. Whether infested host trees are shorter and smaller-crowned because lianas suppress them, or because lianas preferentially colonise already small trees, has remained unresolved. We used a longitudinal dataset of individual liana infestation histories spanning fourteen years (2011-2025), combined with terrestrial laser scanning (TLS)-derived structural metrics for 251 trees across 67 species on Barro Colorado Island, Panama. Bayesian analyses showed that persistently infested trees were shorter (11.0%), with smaller crown projected area (22.3%) and crown volume (25.9%) than never-infested trees; the 95% credible intervals for these effects excluded zero. Pre-infestation crown architecture did not credibly predict subsequent colonisation. These patterns are more consistent with persistent infestation imposing lasting architectural legacies than with strong pre-existing architectural susceptibility, suggesting rising liana abundance may progressively reduce forest stature and canopy density, with implications for tropical carbon storage projections.

ecology↗

bioRxiv2025

Dynamic regulation of neuronal Vault trafficking and RNA cargo by the noncoding RNA, Vaultrc5

Vaults are large ribonucleoprotein complexes of unknown function. Here, we report that the vault-associated noncoding RNA, Vaultrc5, is highly enriched at the synapse and is required for activity-dependent vault trafficking in primary cortical neurons. We have discovered that vaults are comprised of unique populations of coding and non-coding RNA, and that this cargo varies dynamically between subcellular compartments. In addition, Vaultrc5 knockdown at the synapse shifts the RNA cargo toward transcripts associated with immune surveillance, and Vaultrc5 knockdown, in vivo, leads to altered fear extinction learning. These findings suggest that the Vaultrc5 is critically involved in coordinating the experience-dependent trafficking of vaults and related RNA cargo, which may represent a novel feature of neuronal plasticity associated with learning and memory.

neuroscience↗

bioRxiv2025

Genotype-Dependent Response to Water Deficit: Increases in Maize Cell Wall Digestibility Occurs Through Reducing Both p-Coumaric Acid and Lignification of the Rind

The compositional dynamics of the cell wall are influenced by drought, and it has been demonstrated that water deficit induces significant changes in its main components. Moreover, changes in cell wall concentration and distribution in response to water deficit affect maize degradability. This study presents a histological and biochemical analysis of thirteen maize inbred lines, evaluated over two years in Pobra de Brollon (Spain) and Mauguio (France) under contrasting water availability conditions. Our aim was to investigate the environmental and genotypic impacts on histological and biochemical profiles, to assess in vitro cell wall digestibility under water deficit, and to explore how these responses relate to changes in cell wall composition and structure. Overall, we observed greater concentrations of p-coumaric acid under control conditions, with significant decreases in stressed conditions at each location. Histologically, we found an increase in non-lignified tissues under water deficit conditions across all tissues and in both locations. In terms of in vitro cell wall digestibility (IVCWRD), significant increases were detected in response to water deficit. Additionally, genotype-dependent response patterns were evident, revealing two distinct behavioural groups. Notably, in plastic genotypes, increases in IVCWRD in response to water deficit were concomitant to reductions in p-coumaric acid content and a decrease in red-stained lignified tissues in the rind. This study emphasizes the complex, genotype-dependent responses to water deficit, underscoring the important roles of plasticity and stability in shaping the impact on maize cell wall digestibility; paving the way to breed for adapted genotypes to face climate changes. HighlightIncreased digestibility in response to water deficit is genotype-dependent and linked to reductions in p-coumaric acid content and lower lignification of the rind

physiology↗

bioRxiv2024

Cell wall digestibility outperforms ear in maintaining digestibility even under severe combined water and heat stress

CONTEXT OR PROBLEMForage maize is a central pillar of dairy cow feeding in France, directly influencing milk production. Drought significantly affects both maize yield and digestibility, which are both key parameters required for hybrid registration purposes. OBJECTIVE OR RESEARCH QUESTIONResearch on maize inbred lines has revealed droughts notable effect on dry matter and cell wall digestibilities due to changes in cell wall composition, directly impacting forage quality. No such studies have been performed on forage maize hybrids however, which are the main seed type used in the agricultural sector. In this paper, we aimed to understand the impact of water and heat stress on forage maize digestibility, and to uncover the factors controlling it. METHODSWe grew a range of modern forage maize hybrids for two years under four different controlled water stress modalities. These plants were agronomically, biochemically and histologically assayed, allowing us to perform a multiscale analysis to determine the traits responsible for variations in digestibility. RESULTSBy establishing a comprehensive heat and water stress index, we classified the environmental conditions. We demonstrated that under severe stress, ear production decreases significantly, but dry matter digestibility can be maintained through increased cell wall digestibility. This boost in cell wall digestibility was due to a reduction in p-hydroxycinnamic acid content and changes in lignin distribution, while lignin content and structure remained stable. The significant impact of lignin distribution on cell wall digestibility increased with the severity of the stress, reaching an extreme threshold where biochemical parameters solely account for digestibility variations. CONCLUSION AND IMPLICATIONSTo improve maize digestibility, it will be necessary to better understand how the reduction in carbon flux under stress affects p-hydroxycinnamic acid levels without greatly impacting lignin content. Finally, our work suggests that the inclusion of moderate stress conditions in future maize breeding programs will be necessary to better adapt forage maize hybrids to climate change.

plant biology↗

bioRxiv2023

Development and calibration of the FSPM CPlantBox to represent the interactions between water and carbon fluxes in the soil-plant-atmosphere continuum

A plants development is strongly linked to the water and carbon flows in the soil-plant-atmosphere continuum. Expected climate shifts will alter the water and carbon cycles and will affect plant phenotypes. Comprehensive models which simulate mechanistically and dynamically the feedback loops between a plants three-dimensional development and the water and carbon flows are useful tools to evaluate the sustainability of genotype-environment-management combinations which do not yet exist. In this study, we present the latest version of the open-source three-dimensional Functional-Structural Plant Model CPlantBox with PiafMunch and DuMux coupling. We simulated semi-mechanistically the development of generic C3 monocots from 10 to 25 days after sowing and undergoing an atmospheric dry spell of one week (no precipitation). We compared the results for dry spells starting on different days (day 11 or 18) and with different climates (wetter and colder against drier and warmer atmospheric and initial soil conditions). Compared with the wetter and colder climate, the dry spell with the drier and warmer climate led to a lower instantaneous water use efficiency. Moreover, the lower symplasm turgor for the drier and warmer climate limited the growth, which made the sucrose available for other processes, such as maintenance respiration. Both of these effects were stronger for the later dry spell compared with the early dry spell under the drier and warmer climate. We could thus use CPlantBox to simulate diverging emerging processes (like carbon partitioning) defining the plants phenotypic plasticity response to their environment.

plant biology↗

bioRxiv2023

Molecular basis for the interaction of Mint proteins with Munc18-1 and interactome analyses with AlphaFold2

Munc18-interacting proteins (Mints) are multi-domain adaptors that regulate neuronal membrane trafficking, signalling and neurotransmission. Mint1 and Mint2 are highly expressed in the brain with overlapping roles in the regulation of synaptic vesicle fusion required for neurotransmitter release by interacting with the essential synaptic protein Munc18-1. Here, we have used AlphaFold2 to identify and then validate the mechanisms that underpin both the specific interactions of neuronal Mint proteins with Munc18-1 as well as their wider interactome. We find a short acidic -helical motif (AHM) within Mint1 and Mint2 is necessary and sufficient for specific binding to Munc18-1 and binds a conserved surface on Munc18-1 domain3b. In Munc18-1/2 double knockout neurosecretory cells mutation of the Mint-binding site reduces the ability of Munc18-1 to rescue exocytosis, and although Munc18-1 can interact with Mint and Sx1a proteins simultaneously in vitro we find they have mutually reduced affinities, suggesting an allosteric coupling between the proteins. Using AlphaFold2 to then examine the entire cellular network of putative Mint interactors provides a structural model for their assembly with a variety of known and novel regulatory and cargo proteins including ARF3/ARF4 small GTPases, and the AP3 clathrin adaptor complex. Validation of Mint1 interaction with a new predicted binder TJAP1 provides experimental support that AlphaFold2 can correctly predict interactions across such large-scale datasets. Overall, our data provides insights into the diversity of interactions mediated by the Mint family and shows that Mints may help facilitate a key trigger point in SNARE complex assembly and vesicle fusion.

biochemistry↗

bioRxiv2021

Why can we detect lianas from space?

Lianas, woody vines acting as structural parasites of trees, have profound effects on the composition and structure of tropical forests, impacting tree growth, mortality, and forest succession. Remote sensing offers a powerful tool for quantifying the scale of liana infestation, provided the availability of robust detection methods. We analyze the consistency and global specificity of spectral signals from liana-infested tree crowns and forest stands, examining the underlying mechanisms. We compiled a database, including leaf reflectance spectra from 5424 leaves, fine-scale airborne reflectance data from 999 liana-infested canopies, and coarse-scale satellite reflectance data covering hectares of liana-infested forest stands. To unravel the mechanisms of the liana spectral signal, we applied mechanistic radiative transfer models across scales, corroborated by field data on liana leaf chemistry and canopy structure. We find a consistent liana spectral signature at canopy and stand scales across sites. This signature mainly arises at the canopy level due to direct effects of leaf angles, resulting in a larger apparent leaf area, and indirect effects from increased light scattering in the NIR and SWIR regions, linked to lianas less costly leaf construction compared to trees. The existence of a consistent global spectral signal for lianas suggests that large-scale quantification of liana infestation is feasible. However, because the traits identified are not exclusive to lianas, accurate large-scale detection requires rigorously validated remote sensing methods. Our models highlight challenges in automated detection, such as potential misidentification due to leaf phenology, tree life-history, topography, and climate, especially where the scale of liana infestation is less than a single remote sensing pixel. The observed cross-site patterns also prompt ecological questions about lianas adaptive similarities across environments, indicating possible convergent evolution due to shared constraints on leaf biochemical and structural traits. Open data statementOf the 17 datasets used, 10 are published and publicly accessible, with links provided in this submission (Appendix S1: Section S1). Upon acceptance, remaining seven datasets will be provided via Smithsonians Dspace. The open-source model code is available as R-package ccrtm (https://cran.r-project.org/web/packages/ccrtm/index.html) and on github (https://github.com/MarcoDVisser/ccrtm). Code will be archived in Zenodo should the manuscript be accepted for publication

plant biology↗

bioRxiv2021

Liana optical traits increase tropical forest albedo and reduce ecosystem productivity

Lianas are a key growth form in tropical forests. Their lack of self-supporting tissues and their vertical position on top of the canopy make them strong competitors of resources. A few pioneer studies have shown that liana optical traits differ on average from those of colocated tree. Those trait discrepancies were hypothesized to be responsible for the competitive advantage of lianas over trees. Yet, in the absence of reliable modelling tools, it is impossible to unravel their impact on the forest energy balance, light competition and on the liana success in Neotropical forests. To bridge this gap, we performed a meta-analysis of the literature to gather all published liana leaf optical spectra, as well as all canopy spectra measured over different levels of liana infestation. We then used a Bayesian data assimilation framework applied to two radiative transfer models (RTMs) covering the leaf and canopy scales to derive tropical tree and liana trait distributions, which finally informed a full dynamic vegetation model. According to the RTMs inversion, lianas grew thinner, more horizontal leaves with lower pigment concentrations. Those traits made the lianas particularly efficient at light interception and completely modified the forest energy balance and its carbon cycle. While forest albedo increased by 14% in the shortwave, light availability was dramatically reduced in the understory (-30% of the PAR radiation) and soil temperature decreased by 0.5{degrees}C. Those liana-specific traits were also responsible for a significant reduction of tree (-19%) and ecosystem (-7%) gross primary productivity (GPP) while lianas benefited from them (their GPP increased by +27%). This study provides a novel mechanistic explanation to the increase in liana abundance, new evidence of the impact of structural parasitism on forest functioning, and paves the way for the evaluation of the large-scale impacts of woody vines on forest biogeochemical cycles.

plant biology↗

bioRxiv2020

Frontotemporal dementia mutant tau (P301L) locks Fyn in an open, active conformation conducive to nanoclustering

Fyn is a Src kinase that controls critical signalling cascades and its postsynaptic enrichment underpins synaptotoxicity in Alzheimers disease (AD) and frontotemporal dementia (FTLD-tau). Previously, we found that pathogenic FTLD tau mutant (P301L) expression promotes aberrant trapping of Fyn in nanoclusters within hippocampal dendrites via an unknown mechanism (Padmanabhan et al., 2019). Here, we imaged Fyn-mEos2 using single particle tracking photoactivated localization microscopy (sptPALM) to demonstrate that nanoclustering of Fyn in hippocampal dendrites is promoted by Fyns open, primed conformation. Disrupting the auto-inhibitory, closed conformation of Fyn through phospho-inhibition, and perturbation of Fyns SH3 domain increases, Fyns nanoscale trapping. However, inhibition of Fyns catalytic domain has no impact on its mobility. Tau-P301L promotes Fyn lateral trapping via Fyn opening and ensuing increased catalytic activation. Pathogenic tau may therefore drive synaptotoxicity by locking Fyn in an open, catalytically active conformation, leading to postsynaptic entrapment and aberrant signalling cascades.

neuroscience↗

bioRxiv2020

Neuropilin-1 facilitates SARS-CoV-2 cell entry and provides a possible pathway into the central nervous system

The causative agent of the current pandemic and coronavirus disease 2019 (COVID-19) is the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)1. Understanding how SARS-CoV-2 enters and spreads within human organs is crucial for developing strategies to prevent viral dissemination. For many viruses, tissue tropism is determined by the availability of virus receptors on the surface of host cells2. Both SARS-CoV and SARS-CoV-2 use angiotensin-converting enzyme 2 (ACE2) as a host receptor, yet, their tropisms differ3-5. Here, we found that the cellular receptor neuropilin-1 (NRP1), known to bind furin-cleaved substrates, significantly potentiates SARS-CoV-2 infectivity, which was inhibited by a monoclonal blocking antibody against the extracellular b1b2 domain of NRP1. NRP1 is abundantly expressed in the respiratory and olfactory epithelium, with highest expression in endothelial cells and in the epithelial cells facing the nasal cavity. Neuropathological analysis of human COVID-19 autopsies revealed SARS-CoV-2 infected NRP1-positive cells in the olfactory epithelium and bulb. In the olfactory bulb infection was detected particularly within NRP1-positive endothelial cells of small capillaries and medium-sized vessels. Studies in mice demonstrated, after intranasal application, NRP1-mediated transport of virus-sized particles into the central nervous system. Thus, NRP1 could explain the enhanced tropism and spreading of SARS-CoV-2.

microbiology↗

bioRxiv2019

Call for participation: Collaborative benchmarking of functional-structural root architecture models. The case of root water uptake.

Three-dimensional models of root growth, architecture and function are becoming important tools that aid the design of agricultural management schemes and the selection of beneficial root traits. However, while benchmarking is common in many disciplines that use numerical models such as natural and engineering sciences, functional-structural root architecture models have never been systematically compared. The following reasons might induce disagreement between the simulation results of different models: different representation of root growth, sink term of root water and solute uptake and representation of the rhizosphere. Presently, the extent of discrepancies is unknown, and a framework for quantitatively comparing functional-structural root architecture models is required. We propose, in a first step, to define benchmarking scenarios that test individual components of complex models: root architecture, water flow in soil and water flow in roots. While the latter two will focus mainly on comparing numerical aspects, the root architectural models have to be compared at a conceptual level as they generally differ in process representation. Therefore defining common inputs that allow recreating reference root systems in all models will be a key challenge. In a second step, benchmarking scenarios for the coupled problems are defined. We expect that the results of step 1 will enable us to better interpret differences found in step 2. This benchmarking will result in a better understanding of the different models and contribute towards improving them. Improved models will allow us to simulate various scenarios with greater confidence and avoid bugs, numerical errors or conceptual misunderstandings. This work will set a standard for future model development.

plant biology↗

bioRxiv2019

MARSHAL, a novel tool for virtual phenotyping of maize root system hydraulic architectures

Functional-structural root system models combine functional and structural root traits to represent the growth and development of root systems. In general, they are characterized by a large number of growth, architectural and functional root parameters, generating contrasted root systems evolving in a highly nonlinear environment (soil, atmosphere), which makes unclear what impact of each single root system on root system functioning actually is. On the other end of the root system modelling continuum, macroscopic root system models associate to each root system instance a set of plant-scale, easily interpretable parameters. However, as of today, it is unclear how these macroscopic parameters relate to root-scale traits and whether the upscaling of local root traits are compatible with macroscopic parameter measurements. The aim of this study was to bridge the gap between these two modelling approaches by providing a fast and reliable tool, which eventually can help performing plant virtual breeding.\n\nWe describe here the MAize Root System Hydraulic Architecture soLver (MARSHAL), a new efficient and user-friendly computational tool that couples a root architecture model (CRootBox) with fast and accurate algorithms of water flow through hydraulic architectures and plant-scale parameter calculations, and a review of architectural and hydraulic parameters of maize.\n\nTo illustrate the tools potential, we generated contrasted maize hydraulic architectures that we compared with architectural (root length density) and hydraulic (root system conductance) observations. Observed variability of these traits was well captured by model ensemble runs We also analyzed the multivariate sensitivity of mature root system conductance, mean depth of uptake, root system volume and convex hull to the input parameters to highlight the key parameters to vary for efficient virtual root system breeding. MARSHAL enables inverse optimisations, sensitivity analyses and virtual breeding of maize hydraulic root architecture. It is available as an R package, an RMarkdown pipeline, and a web application.\n\nOne-sentence summaryWe developed a dynamic hydraulic-architectural model of the root system, parameterized for maize, to generate contrasted hydraulic architectures, compatible with field and lab observations and that can be further analyzed in soil-root system models for virtual breeding.\n\nAuthors contributionsF.M., X.D., M.J. and G.L. designed the study and defined its scope; F.M. and G.L. developed the model while associated tools were created by A.H. and G.L.; F.M. ran the model simulations and analyzed the results together with M.J and G.L.; F.M. and M.J. wrote the first version of this manuscript; all co-authors critically revised it.

plant biology↗

bioRxiv2019

Diurnal variation in xylem water isotopic signature biases depth of root-water uptake estimates

O_LIStable water isotopes are a powerful and widely used tool to derive the depth of root water uptake (RWU) in lignified plants. Uniform xylem water isotopic signature (i-H2O-xyl) along the length of a lignified plant is a central assumption, which has never been properly evaluated.\nC_LIO_LIHere we studied the effects of diurnal variation in RWU, sap flow velocity and various other soil and plant parameters on i-H2O-xyl signature within a plant using a mechanistic plant hydraulic model.\nC_LIO_LIOur model predicts significant variation in i-H2O-xyl along the full length of an individual plant arising from diurnal RWU fluctuations and vertical soil water heterogeneity. Moreover, significant differences in i-H2O-xyl emerge between individuals with different sap flow velocities. We corroborated our model predictions with field observations from French Guiana and northwestern China. Modelled i-H2O-xyl varied considerably along stem length ranging up to 18.3{per thousand} in {delta}2H and 2.2{per thousand} in {delta}18O, largely exceeding the range of measurement error.\nC_LIO_LIOur results show clear violation of the fundamental assumption of uniform i-H2O-xyl and occurrence of significant biases when using stable isotopes to assess RWU. As a solution, we propose to include monitoring of sap flow and soil water potential for more robust RWU depth estimates.\nC_LI

plant biology↗

bioRxiv2018

Actomyosin-II facilitates long-range retrograde transport of large cargoes by controlling axonal radial contractility

Most mammalian neurons have a narrow axon, which constrains the passage of large cargoes such as autophagosomes that can be larger than the axon diameter. Radial axonal expansion must therefore occur to ensure efficient axonal trafficking. In this study we consistently find that the trafficking speed of various large axonal cargoes is significantly slower than that of small ones, and reveal that the transit of diverse-sized cargoes causes an acute, albeit transient axonal radial expansion, which is immediately restored by constitutive contractility. Using live super-resolution microscopy, we demonstrate that actomyosin-II controls axonal radial contractility and local expansion, and that NM-II filaments associate with periodic F-actin rings via their head domains. Pharmacological inhibition of NM-II activity, significantly increases axon diameter by detaching the NM-II from F-actin, and impacts the trafficking speed, directionality, and overall efficiency of long-range retrograde trafficking. Consequently, prolonged disruption of NM-II activity leads to disruption of periodic actin rings and formation of focal axonal swellings, a hallmark of axonal degeneration.\n\nSummaryAxonal radial contractility and local expansion control the retrograde trafficking of large cargoes. The periodic actomyosin-II network comprises of NM-II filaments and F-actin rings. Loss of actomyosin-II-mediated radial contractility causes defects in axonal trafficking and stability, leading to degeneration.

neuroscience↗

bioRxiv2018

Connecting the dots between computational tools to analyse soil-root water relations

In the recent years, many computational tools, such as image analysis, data management, process-based simulation and upscaling tools, were developed to help quantify and understand water flow in the soil-root system, at multiple scales (tissue, organ, plant and population). Several of these tools work together or, at least, are compatible. However, for the un-informed researcher, they might seem disconnected, forming a unclear and disorganised succession of tools.\n\nIn this article, we present how different pieces of work can be further developed by connecting them to analyse soil-root-water relations in a comprehensive and structured network. This \"explicit network of soil-root computational tools\" informs the reader about existing tools and help them understand how their data (past and future) might fit within the network. We also demonstrate the novel possibilities of scale-consistent parameterizations made possible by the network with a set of case studies from the literature. Finally, we discuss existing gaps in the network and how we can move forward to fill them.\n\nHighlightsMany computational tools exist to quantify water flow in the soil-root system. These tools can be arranged in a comprehensive network that can be leveraged to better interpret experimental data.

plant biology↗