Biology subjects

Rivard, C.

Publications and source records attributed to Rivard, C..

5 recordsLinked to original sources

bioRxiv2026

NRAMP2 controls manganese partitioning between seed coat and embryo to regulate seed vigor

Seed development and germination depend on the coordinated transport of macronutrients and micronutrients, which sustain the embryo and determine seed vigour. Manganese (Mn) is an essential micronutrient involved in various metabolic processes, yet its role in seed development is not well understood. In this study, we investigated manganese (Mn) homeostasis in seeds and identified NRAMP2, a previously characterised trans-Golgi-localised Mn exporter, as a key transporter that controls Mn delivery to the embryo. Promoter analysis showed NRAMP2 expression in the chalazal region, which is a central hub for the exchange of nutrients between maternal tissues and the developing seed. X-ray fluorescence mapping revealed mislocalisation of Mn in nramp2 mutant seeds, retention of Mn on the seed coat and markedly reduced levels of Mn in the embryo. Functionally, Mn depletion delayed seed germination and increased physiological dormancy by reducing reactive oxygen species (ROS) accumulation. Our results uncover the vital role of Mn in supporting embryo development and seed vigour, establishing NRAMP2 as a pivotal component of the Mn transport machinery during seed development.

plant biology↗

bioRxiv2024

Detection of titanium nanoparticles in human, animal and infant formula milk

The sustainability of mammals on Earth relies on milk. During lactation, maternal exposure to pollutants like metal nanoparticles (NPs) can affect offspring development and survival. Despite being banned from food applications in Europe due suspected toxicity, titanium dioxide (TiO2) NPs are still massively manufactured for countless other uses. While contamination of ecosystems is well documented, contamination of mammals remains underexplored. Here, we used synchrotron X-ray fluorescence and single particle inductively coupled plasma mass spectrometry to analyse human, animal, and infant formula milk. Titanium containing micro- and nano-particles were detected in all samples, regardless of the species, location, and processing. We identified varying concentrations, sizes, and combinations of rutile and anatase TiO2, ilmenite FeTiO3 and possibly titanite CaTiSiO5 or pseudobrookite Fe2TiO5. These findings suggest that milk serves as a carrier for titanium-containing nanomaterials to expose newborns on a daily basis until weaning.

physiology↗

bioRxiv2020

Small Cell Lung Cancer Neuroendocrine Subtypes are Associated with Different Immune Microenvironment and Checkpoint Molecule Distribution

Small cell lung cancer (SCLC) has recently been sub-categorized into neuroendocrine (NE)- high and NE-low subtypes showing immune desert and immune oasis phenotypes, respectively. We aimed to characterize the immune cell localization and the microenvironment according to immune checkpoints and NE subtypes in human SCLC tissue samples at the protein level. In this cross-sectional study, we included 32 primary tumors and matched lymph node (LN) metastases of resected early-stage, histologically confirmed SCLC patients, which were previously clustered into NE subtypes using NE-associated key RNA genes. Immunohistochemistry (IHC) was performed on FFPE TMAs with antibodies against CD45, CD3, CD8 and immune checkpoints including poliovirus receptor (PVR) and Indoleamine 2,3-dioxygenase (IDO). According to our results, the stroma was significantly more infiltrated by immune cells both in primary tumors and LN metastases (vs tumor cell nests). Immune (CD45+) cell density was significantly higher in tumor nests (110.6 {+/-} 24.95 vs 42.74 {+/-} 10.30, cell/mm2, p= 0.0048), with increased CD8+ effector T cell infiltration (21.81 {+/-} 5.458 vs 3.16 {+/-} 1.36 cell/mm2, p < 0.001) in NE-low vs NE-high tumors. Furthermore, the expression of IDO was confirmed on stromal and endothelial cells, and it positively correlated (r= 0.755, p<0.01) with higher immune cell density both in primary tumors and LN metastases, regardless of the NE pattern. Expression of IDO in tumor nests was significantly higher in NE-low (vs NE-high) primary tumors. PVR expression was significantly higher in NE-low (vs NE-high) patients both in primary tumors) and LN metastases. To our knowledge, this is the first human study that demonstrates in situ that NE-low tumors are associated with increased immune cell infiltration compared to NE-high tumors. PVR and IDO are potential new targets in SCLC, with increased expression in the NE-low subtype, providing key insight for further prospective studies on potential biomarkers and targets for SCLC immunotherapies.

cancer biology↗

bioRxiv2019

Integration of system phenotypes in microbiome networks to identify candidate synthetic communities: a study of the grafted tomato rhizobiome

Understanding factors influencing microbial interactions, and designing methods to identify key taxa, are complex challenges for achieving microbiome-based agriculture. Here we study how grafting and the choice of rootstock influence root-associated fungal communities in a grafted tomato system. We studied three tomato rootstocks (BHN589, RST-04-106 and Maxifort) grafted to a BHN589 scion and profiled the fungal communities in the endosphere and rhizosphere by sequencing the Internal Transcribed Spacer (ITS2). The data provided evidence for a rootstock effect (explaining ~2% of the total captured variation, p < 0.01) on the fungal community. Moreover, the most productive rootstock, Maxifort, supported greater fungal species richness than the other rootstocks or controls. We then constructed a phenotype-OTU network analysis (PhONA) using an integrated machine learning and network analysis approach based on sequence-based fungal Operational Taxonomic Units (OTUs) and associated tomato yield data. PhONA provides a graphical framework to select a testable and manageable number of OTUs to support microbiome-enhanced agriculture. We identified differentially abundant OTUs specific to each rootstock in both endosphere and rhizosphere compartments. Subsequent analyses using PhONA identified OTUs that were directly associated with tomato fruit yield, and others that were indirectly linked to yield through their links to these OTUs. Fungal OTUs that are directly or indirectly linked with tomato yield may represent candidates for synthetic communities to be explored in agricultural systems. IMPORTANCEThe realized benefits of microbiome analyses for plant health and disease management are often limited by the lack of methods to select manageable and testable synthetic microbiomes. We evaluated the composition and diversity of root-associated fungal communities from grafted tomatoes. We then constructed a phenotype-OTU network analysis (PhONA) using these linear and network models. By incorporating yield data in the network, PhONA identified OTUs that were directly predictive of tomato yield, and others that were indirectly linked to yield through their links to these OTUs. Follow-up functional studies of taxa associated with effective rootstocks, identified using approaches like PhONA, could support the design of synthetic fungal communities for microbiome-based crop production and disease management. The PhONA framework is flexible for incorporation of other phenotypic data and the underlying models can readily be generalized to accommodate other microbiome or other omics data.

ecology↗

bioRxiv2018

Rootstocks shape the rhizobiome: Rhizosphere and endosphere bacterial communities in the grafted tomato system

Root-associated microbes are critical to plant health and performance, although understanding of the factors that structure these microbial communities and theory to predict microbial assemblages are still limited. Here we use a grafted tomato system to study the effects of rootstock genotypes and grafting in endosphere and rhizosphere microbiomes that were evaluated by sequencing 16S rRNA. We compared the microbiomes of nongrafted tomato cultivar BHN589, selfgrafted BHN589, and BHN589 grafted to Maxifort or RST-04-106 hybrid rootstocks. OTU-based bacterial diversity was greater in Maxifort compared to nongraft controls, whereas bacterial diversity in the controls (selfgraft and nongraft) and the other rootstock (RST-04-106) was similar. Grafting itself did not affect bacterial diversity; diversity in the selfgraft was similar to the nongraft. Bacterial diversity was higher in the rhizosphere than in the endosphere for all treatments. However, despite the lower overall diversity, there was a greater number of differentially abundant OTUs (DAOTUs) in the endosphere, with the greatest number of DAOTUs associated with Maxifort. In a PERMANOVA analysis, there was evidence for an effect of rootstock genotype on bacterial communities. The endosphere-rhizosphere compartment and study site explained a high percentage of the differences among bacterial communities. Further analyses identified OTUs responsive to rootstock genotypes in both the endosphere and the rhizosphere. Our findings highlight the effects of rootstocks on bacterial diversity and composition. The influence of rootstock and plant compartment on microbial communities indicates opportunities for the development of designer communities and microbiome-based breeding to improve future crop production.\n\nImportanceUnderstanding factors that control microbial communities is essential for designing and supporting microbiome-based agriculture. In this study, we used a grafted tomato system to study the effect of rootstock genotypes and grafting on bacterial communities colonizing the endosphere and the rhizosphere. Comparing the bacterial communities in control treatments (nongraft and selfgraft plants) with the hybrid rootstocks used by farmers, we evaluated the effect of rootstocks on overall bacterial diversity and composition. These findings indicate the potential for using plant genotype to indirectly select bacterial taxa. In addition, we identify taxa responsive to each rootstock treatments, which may represent candidate taxa useful for biocontrol and in biofertilizers.

microbiology↗