Biology subjects

Cloutier, M.

Publications and source records attributed to Cloutier, M..

10 recordsLinked to original sources

bioRxiv2026

MillionTrees: A global benchmark for tree detection across geography, sensor, and annotation geometry

Airborne tree monitoring using remotely sensed data, combined with the growth of computer vision models for object detection and segmentation, can facilitate broad scale assessment of tree health, ecology and ecosystem function. However, datasets for airborne tree detection have been largely limited to a single geography, resolution, or annotation approach, making it difficult to develop general models and benchmark their utility for broad applications. We compile existing and newly published annotation datasets to create a comprehensive dataset for training and evaluating airborne tree detection in RGB imagery. The MillionTrees dataset has over a million individual trees from a broad range of forest types, tree species, and geographic locations. In addition, it has six million weakly supervised annotations from a range of sources including airborne LiDAR and photogrammetry, arborist surveys, and simulated landscapes. An evaluation standard is provided to facilitate rapid model development. We benchmark several existing tree detection algorithms and demonstrate that while current open-source models do not generalize across the diverse datasets in the benchmark, training on MillionTrees improves both within-domain and out-of-domain performance. Held-out validation datasets using ground truth derived from terrestrial LiDAR paired with overhead RGB show that overfitting to test data is common and hyperparameter tuning is an underappreciated challenge towards a global zero shot tree detection method. We discuss the limitations of the currently available data for airborne RGB tree detection, how to create more robust evaluation data and the need for better understanding of the uncertainty and utility of tree detection from airborne remote sensing.

ecology↗

bioRxiv2025

Pantoea ananatis-triggered systemic resistance requires root sensing through the LORE receptor kinase in Arabidopsis

Systemic immunity induced by beneficial bacteria helps plants to cope with subsequent pathogen attacks. However, how these bacteria are sensed by plants and how this sensing results in a systemic response is not well understood. Recently, the Brassicaceae LIPOOLIGOSACCHARIDE-SPECIFIC REDUCED ELICITATION (LORE) receptor kinase was identified as the direct sensor of bacterial medium-chain-length 3-hydroxy fatty acids (mc-3-OH-FAs) and 3-(3-hydroxyalkanoyloxy)alkanoic acids (HAAs), which activate systemic Brassicaceae immunity. Here, we show that the bacterium Pantoea ananatis BRT175, which produces HAAs, can colonize Arabidopsis thaliana roots independently of the production of these compounds. P. ananatis triggers induced systemic resistance (ISR) to the necrotrophic pathogen Botrytis cinerea, but not to the hemibiotrophic pathogen Pseudomonas syringae pv. tomato. Importantly, this ISR can be mimicked by HAAs or 3-hydroxy-decanoic acid (3-OH-C10). Both P. ananatis-triggered and 3-OH-C10-triggered ISR against B. cinerea are mediated by LORE sensing, involve salicylic acid, jasmonic acid and ethylene signaling pathways, and activate the expression of similar defense genes in infected leaves. Thus, 3-OH-C10 and HAAs are perceived by a pattern recognition receptor (PRR) in the root and activate a local immune response in roots as well as systemic immunity in leaves. Our study demonstrates that these lipidic microbe-associated molecular patterns (MAMPs), produced by beneficial microorganisms, are necessary and sufficient to trigger rhizobacteria-driven ISR. It further highlights the role of these MAMPs in differentially activating systemic resistance against biotrophic and necrotrophic pathogens.

plant biology↗

bioRxiv2025

Fluorescence in situ hybridization (FISH) and detection of Bacteria and Archaea cells in fecal samples

Oligonucleotide probes have been used to detect bacteria and archaea that colonize the cattle and pig digestive system. The Fluorescent in situ hybridization (FISH) is a molecular biology technique that uses oligonucleotides of 15 to 25 nucleotides of length associated with a fluorescent molecule. In microbiology, the FISH technique utilizes probes targeting ribosomal RNA (rRNA). It is one amongst others, a staining technique that allows the identification, detection and quantification of microorganisms without prior cultivation by means of epifluorescence and confocal laser scanning microscopy (CLSM). In this study, we describe the usage of the confocal laser scanning microscopy coupled with fluorescence in situ hybridization (FISH), in order to detect and quantify of bacteria and archaea in fecal samples from cattles manure and swine slurry.

microbiology↗

bioRxiv2024

deadtrees.earth - An Open-Access and Interactive Database for Centimeter-Scale Aerial Imagery to Uncover Global Tree Mortality Dynamics

Excessive tree mortality is a global concern and remains poorly understood as it is a complex phenomenon. We lack global and temporally continuous coverage on tree mortality data. Ground-based observations on tree mortality, e.g., derived from national inventories, are very sparse, not standardized and not spatially explicit. Earth observation data, combined with supervised machine learning, offer a promising approach to map tree mortality over time. However, global-scale machine learning requires broad training data covering a wide range of environmental settings and forest types. Drones provide a cost-effective source of training data by capturing high-resolution orthophotos of tree mortality events at sub-centimeter resolution. Here, we introduce deadtrees.earth, an open-access platform hosting more than a thousand centimeter-resolution orthophotos, covering already more than 300,000 ha, of which more than 58,000 ha are fully annotated. This community-sourced and rigorously curated dataset shall serve as a foundation for a global initiative to gather comprehensive reference data. In concert with Earth observation data and machine learning it will serve to uncover tree mortality patterns from local to global scales. This will provide the foundation to attribute tree mortality patterns to environmental changes or project tree mortality dynamics to the future. Thus, the open and interactive nature of deadtrees.earth together with the collective effort of the community is meant to continuously increase our capacity to uncover and understand tree mortality patterns.

ecology↗

bioRxiv2023

Influence of Temperate Forest Autumn Leaf Phenology on Segmentation of Tree Species from UAV Imagery Using Deep Learning

Remote sensing of forests has become increasingly accessible with the use of unoccupied aerial vehicles (UAV), along with deep learning, allowing for repeated high-resolution imagery and the capturing of phenological changes at larger spatial and temporal scales. In temperate forests during autumn, leaf senescence occurs when leaves change colour and drop. However, the influence of leaf senescence in temperate forests on tree species segmentation using a Convolutional Neural Network (CNN) has not yet been evaluated. Here, we acquired high-resolution UAV imagery over a temperate forest in Quebec, Canada on seven occasions between May and October 2021. We segmented and labelled 23,000 tree crowns from 14 different classes to train and validate a CNN for each imagery acquisition. The CNN-based segmentation showed the highest F1-score (0.72) at the start of leaf colouring in early September and the lowest F1-score (0.61) at peak fall colouring in early October. The timing of the events occurring during senescence, such as leaf colouring and leaf fall, varied substantially between and within species and according to environmental conditions, leading to higher variability in the remotely sensed signal. Deciduous and evergreen tree species that presented distinctive and less temporally-variable traits between individuals were better classified. While tree segmentation in a heterogenous forest remains challenging, UAV imagery and deep learning show high potential in mapping tree species. Our results from a temperate forest with strong leaf colour changes during autumn senescence show that the best performance for tree species segmentation occurs at the onset of this colour change.

ecology↗

bioRxiv2022

The Fc-effector function of COVID-19 convalescent plasma contributes to SARS-CoV-2 treatment efficacy in mice

COVID-19 convalescent plasmas (CCPs) are chosen for plasma therapy based on neutralizing titers and anti-Spike immunoglobulin levels. However, specific CCP characteristics that promote SARS-CoV-2 control in recipients are complex and incompletely defined. Using an in vivo imaging approach, we demonstrate that CCPs with low neutralizing and high Fc-effector activity, in contrast to those with poor Fc-function, afford effective prophylaxis and therapy in K18-hACE2 mice lethally challenged with SARS-CoV-2-nLuc. Macrophages and neutrophils significantly contributed to CCP effects during therapy but to a reduced extent under prophylaxis. Both IgG and Ig(M+A) were required during therapy, but the IgG fraction alone was sufficient during prophylaxis. Finally, despite neutralizing poorly, SARS-CoV-2 Wuhan-elicited CCPs delayed Delta and Beta variants of concern (VOC)-induced mortality in mice illustrating the contribution of polyclonal Fc-effector functions in immunity against VOCs. Thus, in addition to neutralization, Fc-effector activity is a significant criterion for CCP selection for therapeutic applications.

immunology↗

bioRxiv2020

Rhamnolipids and their 3-(3-hydroxyalkanoyloxy)alkanoic acid precursors activate Arabidopsis innate immunity through two independent mechanisms

Plant innate immunity is activated upon perception of invasion pattern molecules by plant cell-surface immune receptors. Several bacteria of the genera Pseudomonas and Burkholderia produce rhamnolipids (RLs) from L- rhamnose and (R)-3-hydroxyalkanoate precursors (HAAs). RL and HAA secretion is required to modulate bacterial surface motility, biofilm development, and thus successful colonization of hosts. Here, we show that the lipidic secretome from the opportunistic pathogen Pseudomonas aeruginosa mostly comprising RLs and HAAs stimulates Arabidopsis immunity. We demonstrate that HAAs are sensed by the bulb-type lectin receptor kinase LIPOOLIGOSACCHARIDE-SPECIFIC REDUCED ELICITATION/S-DOMAIN-1-29 (LORE/SD1-29) that also mediates medium-chain 3-hydroxy fatty acid (mc-3-OH-FA) perception in the plant Arabidopsis thaliana. HAA sensing induces canonical immune signaling and local resistance to plant pathogenic Pseudomonas infection. By contrast, RLs trigger an atypical immune response and resistance to Pseudomonas infection independent of LORE. Thus, the glycosyl moieties of RLs, albeit abolishing sensing by LORE, do not impair their ability to trigger plant defense. In addition, our results show that RL-triggered immune response is affected by the sphingolipid composition of the plasma membrane. In conclusion, RLs and their precursors released by bacteria can both be perceived by plants but through distinct mechanisms. SignificanceActivation of plant innate immunity relies on the perception of microorganisms through self and nonself elicitors. Rhamnolipids and their precursor HAAs are exoproducts produced by beneficial and pathogenic bacteria. They are involved in bacterial surface dissemination and biofilm development. As these compounds are released in the extracellular milieu, they have the potential to be perceived by the plant immune system. Our work shows that both compounds independently activate plant immunity. We demonstrate that HAAs are perceived by the receptor protein kinase LORE. By contrast, rhamnolipids are not senses by LORE but activate a non-canonical immune response affected by the sphingolipid composition of the plant plasma membrane. Thus, plants are able to sense bacterial molecules as well as their direct precursors to trigger a distinct immune response.

plant biology↗

bioRxiv2020

Major role of IgM in the neutralizing activity of convalescent plasma against SARS-CoV-2

Characterization of the humoral response to SARS-CoV-2, the etiological agent of Covid-19, is essential to help control the infection. In this regard, we and others recently reported that the neutralization activity of plasma from COVID-19 patients decreases rapidly during the first weeks after recovery. However, the specific role of each immunoglobulin isotype in the overall neutralizing capacity is still not well understood. In this study, we selected plasma from a cohort of Covid-19 convalescent patients and selectively depleted immunoglobulin A, M or G before testing the remaining neutralizing capacity of the depleted plasma. We found that depletion of immunoglobulin M was associated with the most substantial loss of virus neutralization, followed by immunoglobulin G. This observation may help design efficient antibody-based COVID-19 therapies and may also explain the increased susceptibility to SARS-CoV-2 of autoimmune patients receiving therapies that impair the production of IgM.

microbiology↗

bioRxiv2020

Cytokine priming of naive CD8+ T lymphocytes modulates chromatin accessibility that partially overlaps with changes induced by antigen simulation

BackgroundNaive CD8+ T lymphocytes undergo antigen non-specific proliferation following exposure to certain synergistic combination of inflammatory (IL-6, IL-21) and homeostatic (IL-7, IL-15) cytokines. Such cytokine-stimulated naive CD8+ T cells display increased T cell antigen receptor (TCR) sensitivity, allowing them to respond to limiting concentrations of cognate antigenic peptides and altered peptide ligands of lower affinity towards the TCR. The purpose of this study is to gain insight into the molecular mechanisms of such cytokine priming. MethodsNaive CD8+ T lymphocytes expressing the PMEL-1 transgenic TCR were stimulated with IL-15 and IL-21, and chromatin accessibility was assessed using the assay for transposase-accessible chromatin (ATAC) sequencing. Cells stimulated by the cognate antigenic peptide mgp10025-33 were used as controls. ResultsCompared to naive cells, cytokine-primed cells showed 212 opening and 484 closing peaks, whereas antigen-stimulated cells showed 12087 opening and 6982 closing peaks. However, a significant fraction of the opening (33%) and closing (63%) peaks of cytokine-primed cells overlapped with those of the antigenic stimulated cells. Chromatin accessibility peaks modulated in cytokine-primed cells were strongly represented in gene ontology pathways for T cell signaling, activation, regulation and effector functions. Many of the transcription factor binding motifs located close to the opening and closing peaks of cytokine-primed cells also occurred in antigen-stimulated cells. ConclusionsOur data suggest that by modulating the gene expression programs involved in TCR signaling, cytokine priming induces a poised state that lowers the TCR signaling threshold in naive CD8+ T cells and increases their antigen responsiveness.

immunology↗

bioRxiv2020

SILAC proteomics implicates the ubiquitin conjugating enzyme UBE2D in SOCS1-mediated downmodulation of the MET receptor in hepatocytes

Suppressor of Cytokine Signaling 1 (SOCS1) functions as a tumor suppressor in hepatocellular carcinoma (HCC) and many other types of cancers. SOCS1 mediates its functions by inhibiting tyrosine kinases, promoting ubiquitination and proteasomal degradation of signal transducing proteins, and by modulating transcription factors. Here, we studied the impact of SOCS1 on the hepatocyte proteome using Stable Isotopic Labelling of Amino acids in Cell culture (SILAC)-based mass spectrometry on the Hepa1-6 murine HCC cell line stably expressing wildtype SOCS1 or a mutant SOCS1 with impaired SH2 domain. As SOCS1 regulates the hepatocyte growth factor (HGF) receptor MET, the SILAC-labelled cells were stimulated or not with HGF. Following mass spectrometry analysis, differentially modulated proteins were identified, quantified and analyzed for pathway enrichment. Of the 3440 proteins identified in Hepa-SOCS1 cells at steady state, 181 proteins were significantly modulated compared to control cells. The SH2 domain mutation and HGF increased the number of differentially modulated proteins. Protein interaction network analysis revealed enrichment of SOCS1-modulated proteins within multiprotein complexes such as ubiquitin conjugating enzymes, proteasome, mRNA spliceosome, mRNA exosome and mitochondrial ribosome. These findings suggest that SOCS1, induced by cytokines, growth factors and diverse other stimuli, may dynamically modulate of large macromolecular regulatory complexes to help maintain cellular homeostasis. Notably, the expression of UBE2D ubiquitin conjugating enzyme, which is implicated in the control of growth factor receptor tyrosine kinase signaling, was found to be regulated by SOCS1.

molecular biology↗