Biology subjects

Deleu, M.

Publications and source records attributed to Deleu, M..

6 recordsLinked to original sources

bioRxiv2026

A bacterial lipid triggers membrane mechanosensing immunity in Arabidopsis

The plant immune system engages cell-surface receptors that detect microbe-associated molecular patterns to initiate pattern-triggered immunity (PTI), and intracellular receptors that sense microbe-secreted effectors to activate effector-triggered immunity (ETI). Whether additional modes of microbial detection exist remains unclear. Here, we define membrane mechanosensing immunity (MSI), a third layer of immune signaling. A bacterial lipid, the main diffusible signal factor (DSF) from Xanthomonas campestris pv. campestris, acts as a membrane-active molecule that alters plasma membrane biophysical properties, activates Mechanosensitive Channel of Small Conductance (MscS)-like (MSL)-dependent immune signaling, and triggers a broad transcriptional reprogramming that overlaps with PTI and ETI. MSI modulates PTI signaling and requires both PTI and ETI components for effective disease resistance. These findings establish the sensing of metabolite-induced membrane perturbations as a mechanism of microbial detection.

plant biology↗

bioRxiv2024

Dual action of sphinganine in the plant disease resistance to bacteria.

Sphingolipids are ubiquitous, highly diverse molecules constituting at least 40% of plant plasma membranes. Initially known as modulators of membrane integrity, they now emerge as important players in plant responses to (a)biotic stresses. The interaction between Arabidopsis thaliana and the bacterium Pseudomonas syringae pv. tomato DC3000 AvrRpm1 (Pst AvrRpm1) culminates in the activation of a programmed cell death known as the hypersensitive response, which is part of the plant immune response. In this study, we showed that the co-infiltration of Pst AvrRpm1 and sphinganine (d18:0) in Arabidopsis leaves suppress the hypersensitive response. This suppression phenotype is also observed with bacteria carrying the effectors AvrB and AvrPphB but not with the ones carrying AvrRpt2 and AvrRps4. Sphingolipid-induced hypersensitive response suppression by Pst AvrRpm1 is correlated with the down-regulation of the gene AtNMT1 encoding a N-myristoyltransferase. d18:0 does not have a direct antibacterial effect and its co-infiltration in plants does not display typical signs of immune response such as activation of salicylic acid signaling pathway and extracellular reactive oxygen species production. Biophysical studies showed that d18:0 interacts with plant plasma membrane lipids. More specifically, d18:0 disturbs plant plasma membrane organization and mechanical properties. Our results demonstrate that sphingolipids play an important role in plant resistance, especially by interfering with the plasma membrane organization and effector localization and thus disturbing their function and subsequent immune responses.

plant biology↗

bioRxiv2023

Mechanosensing and Sphingolipid-Docking Mediate Lipopetide-Induced Immunity in Arabidopsis

Bacteria-derived lipopeptides are immunogenic triggers of host defenses in metazoans and plants. Root-associated rhizobacteria produce cyclic lipopeptides that activate systemically induced resistance (IR) against microbial infection in various plants. How these molecules are perceived by plant cells remains elusive. Here, we reveal that immunity activation in Arabidopsis thaliana by the lipopeptide elicitor surfactin is mediated by docking into specific sphingolipid-enriched domains and relies on host membrane deformation and subsequent activation of mechanosensitive ion channels. This mechanism leads to host defense potentiation and resistance to the necrotroph B. cinerea but is distinct from host pattern recognition receptor-mediated immune activation and reminiscent of damage-induced plant immunity.

plant biology↗

bioRxiv2021

Surfactin stimulated by pectin molecular patterns and root exudates acts as a key driver of Bacillus-plant mutualistic interaction

Bacillus velezensis is considered as model species belonging to the so-called B. subtilis complex that typically evolved to dwell in the soil rhizosphere niche and establish intimate association with plant roots. This bacterium provides protection to its natural host against diseases and represents one of the most promising biocontrol agents. However, the molecular basis of the cross-talk that this bacterium establishes with its natural host has been poorly investigated. We show here that these plant-associated bacteria have evolved some polymer-sensing system to perceive their host and that in response, they increase the production of the surfactin-type lipopeptide. Furthermore, we demonstrate that surfactin synthesis is favoured upon growth on root exudates and that this lipopeptide is a key component used by the bacterium to optimize biofilm formation, motility and early root colonization. In this specific nutritional context, the bacterium also modulates qualitatively the pattern of surfactin homologues co-produced in planta and mainly forms variants that are the most active at triggering plant immunity. Surfactin represents a shared good as it reinforces the defensive capacity of the host. ImportanceWithin the plant-associated microbiome, some bacterial species are of particular interest due to the disease protective effect they provide via direct pathogen suppression and/or stimulation of host immunity. While these biocontrol mechanisms are quite well characterized, we still poorly understand the molecular basis of the cross talk these beneficial bacteria initiate with their host. Here we show that the model species Bacillus velezensis stimulates production of the surfactin lipopeptide upon sensing pectin as cell surface molecular pattern and upon feeding on root exudates. Surfactin favors bacterial rhizosphere fitness on one hand and primes the plant immune system on the other hand. Our data therefore illustrate how both partners use this multifunctional compound as unique shared good to sustain mutualistic interaction.

microbiology↗

bioRxiv2020

Purification, characterization and influence on membrane properties of the plant-specific sphingolipids GIPC

The plant plasma membrane (PM) is an essential barrier between the cell and the external environment. The PM is crucial for signal perception and transmission. It consists of an asymmetrical lipid bilayer made up of three different lipid classes: sphingolipids, sterols and phospholipids. The most abundant sphingolipids in the plant PM are the Glycosyl Inositol Phosphoryl Ceramides (GIPCs), representing up to 40% of total sphingolipids, assumed to be almost exclusively in the outer leaflet of the PM. In this study, we investigated the structure of GIPCs and their role in membrane organization. Since GIPCs are not commercially available, we developed a protocol to extract and isolate GIPC-enriched fractions from eudicots (cauliflower and tobacco) and monocots (leek and rice). Lipidomic analysis confirmed the presence of different long chain bases and fatty acids. The glycan head groups of the different GIPC series from monocots and dicots were analysed by GC-MS showing different sugar moieties. Multiple biophysics tools namely Langmuir monolayer, {zeta}-Potential, light scattering, neutron reflectivity, solid state 2H-NMR and molecular modelling were used to investigate the physical properties of the GIPCs, as well as their interaction with free and conjugated phytosterols. We showed that GIPCs increase the thickness and electronegativity of model membranes, interact differentially with the phytosterols species and regulate the gel-to-fluid phase transition during temperature variations.

plant biology↗

bioRxiv2018

Multiple C2 domains and Transmembrane region Proteins (MCTPs) tether membranes at plasmodesmata

AO_SCPLOWBSTRACTC_SCPLOWIn eukaryotes, membrane contact sites (MCS) allow direct communication between organelles. Plants have evolved unique MCS, the plasmodesmata intercellular pores, which combine endoplasmic reticulum (ER) - plasma membrane (PM) contacts with regulation of cell-to-cell signalling. The molecular mechanism and function of membrane tethering within plasmodesmata remains unknown.\n\nHere we show that the Multiple C2 domains and Transmembrane region Protein (MCTP) family, key regulators of cell-to-cell signalling in plants, act as ER - PM tethers specifically at plasmodesmata. We report that MCTPs are core plasmodesmata proteins that insert into the ER via their transmembrane region whilst their C2 domains dock to the PM through interaction with anionic phospholipids. A mctp3/4 loss-of-function mutant induces plant developmental defects while MCTP4 expression in a yeast {Delta}tether mutant partially restores ER-PM tethering. Our data suggest that MCTPs are unique membrane tethers controlling both ER-PM contacts and cell-cell signalling.

plant biology↗