Publications by authors named "Magali Deleu"

55 Publications

A compartmentalized microsystem helps understanding the uptake of benzo[a]pyrene by fungi during soil bioremediation processes.

Sci Total Environ 2021 Aug 17;784:147151. Epub 2021 Apr 17.

Université de technologie de Compiègne, ESCOM, TIMR (Integrated Transformations of Renewable Matter), Centre de Recherche Royallieu - CS 60 319 - 60 203 Compiègne Cedex, France. Electronic address:

Hydrophobic organic soil contaminants such as polycyclic aromatic hydrocarbons (PAH) are poorly mobile in the aqueous phase and tend to sorb to the soil matrix, resulting in low bioavailability. Some filamentous fungi are efficient in degrading this kind of pollutants. However, the mechanism of mobilization of hydrophobic compounds by non-motile microorganisms such as filamentous fungi needs investigations to improve pollutant bioavailability and bioremediation efficiency. Usual homogeneous media for microbial growth in the lab are poorly suited to model the soil, which is a compartmentalized and heterogeneous habitat. A microfluidic device was designed to implement a compartmentalization of the fungal inoculum and the source of the pollutant benzo[a]pyrene (BaP) as a deposit of solid crystals in order to gain a further insight into the mechanisms involved in the access to the contaminant and its uptake in soils. Thus in this device, two chambers are connected by an array of parallel microchannels that are wide enough to allow individual hyphae to grow through them. Macro-cultures of Talaromyces helicus in direct contact with BaP have shown its uptake and intracellular storage in lipid bodies despite the low propensity of BaP to cross aqueous phases as shown by simulation. Observations of T. helicus in the microfluidic device through laser scanning confocal microscopy indicate preferential uptake of BaP at a close range and through contact with the cell wall. However faint staining of some hyphae before contact with the deposit also suggests an extracellular transport phenomenon. Macro-culture filtrates analyses have shown that T. helicus releases extracellular non-lipidic surface-active compounds able to lower the surface tension of culture filtrates to 49.4 mN/m. Thus, these results highlight the significance of active mechanisms to reach hydrophobic contaminants before their uptake by filamentous fungi in compartmentalized micro-environments and the potential to improve them through biostimulation approaches for soil mycoremediation.
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http://dx.doi.org/10.1016/j.scitotenv.2021.147151DOI Listing
August 2021

Biophysical analysis of the plant-specific GIPC sphingolipids reveals multiple modes of membrane regulation.

J Biol Chem 2021 Jan-Jun;296:100602. Epub 2021 Mar 27.

Laboratoire de Biogènese Membranaire, UMR 5200, CNRS, Université de Bordeaux, Villenave d'Ornon Cedex, France. Electronic address:

The plant plasma membrane (PM) is an essential barrier between the cell and the external environment, controlling signal perception and transmission. It consists of an asymmetrical lipid bilayer made up of three different lipid classes: sphingolipids, sterols, and phospholipids. The glycosyl inositol phosphoryl ceramides (GIPCs), representing up to 40% of total sphingolipids, are assumed to be almost exclusively in the outer leaflet of the PM. However, their biological role and properties are poorly defined. In this study, we investigated the role of GIPCs in membrane organization. Because 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 trihydroxylated long chain bases and 2-hydroxylated very long-chain fatty acids up to 26 carbon atoms. The glycan head groups of the GIPCs from monocots and dicots were analyzed by gas chromatograph-mass spectrometry, revealing different sugar moieties. Multiple biophysics tools, namely Langmuir monolayer, ζ-Potential, light scattering, neutron reflectivity, solid state 2H-NMR, and molecular modeling, 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 different phytosterols species, and regulate the gel-to-fluid phase transition during temperature variations. These results unveil the multiple roles played by GIPCs in the plant PM.
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http://dx.doi.org/10.1016/j.jbc.2021.100602DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8099651PMC
March 2021

The Surfactin-Like Lipopeptides From spp.: Natural Biodiversity and Synthetic Biology for a Broader Application Range.

Front Bioeng Biotechnol 2021 2;9:623701. Epub 2021 Mar 2.

Microbial Processes and Interactions, TERRA Teaching and Research Centre, Joint Research Unit BioEcoAgro, UMRt 1158, Gembloux Agro-Bio Tech, University of Liège, Avenue de la Faculté, Gembloux, Belgium.

Surfactin is a lipoheptapeptide produced by several species and identified for the first time in 1969. At first, the biosynthesis of this remarkable biosurfactant was described in this review. The peptide moiety of the surfactin is synthesized using huge multienzymatic proteins called NonRibosomal Peptide Synthetases. This mechanism is responsible for the peptide biodiversity of the members of the surfactin family. In addition, on the fatty acid side, fifteen different isoforms (from C12 to C17) can be incorporated so increasing the number of the surfactin-like biomolecules. The review also highlights the last development in metabolic modeling and engineering and in synthetic biology to direct surfactin biosynthesis but also to generate novel derivatives. This large set of different biomolecules leads to a broad spectrum of physico-chemical properties and biological activities. The last parts of the review summarized the numerous studies related to the production processes optimization as well as the approaches developed to increase the surfactin productivity of cells taking into account the different steps of its biosynthesis from gene transcription to surfactin degradation in the culture medium.
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http://dx.doi.org/10.3389/fbioe.2021.623701DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7960918PMC
March 2021

The Trypanosoma Brucei KIFC1 Kinesin Ensures the Fast Antibody Clearance Required for Parasite Infectivity.

iScience 2020 Aug 20;23(9):101476. Epub 2020 Aug 20.

Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles, 12, rue des professeurs Jeener et Brachet, 6041 Gosselies, Belgium. Electronic address:

Human innate immunity to Trypanosoma brucei involves the trypanosome C-terminal kinesin TbKIFC1, which transports internalized trypanolytic factor apolipoprotein L1 (APOL1) within the parasite. We show that TbKIFC1 preferentially associates with cholesterol-containing membranes and is indispensable for mammalian infectivity. Knockdown of TbKIFC1 did not affect trypanosome growth in vitro but rendered the parasites unable to infect mice unless antibody synthesis was compromised. Surface clearance of Variant Surface Glycoprotein (VSG)-antibody complexes was far slower in these cells, which were more susceptible to capture by macrophages. This phenotype was not due to defects in VSG expression or trafficking but to decreased VSG mobility in a less fluid, stiffer surface membrane. This change can be attributed to increased cholesterol level in the surface membrane in TbKIFC1 knockdown cells. Clearance of surface-bound antibodies by T. brucei is therefore essential for infectivity and depends on high membrane fluidity maintained by the cholesterol-trafficking activity of TbKIFC1.
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http://dx.doi.org/10.1016/j.isci.2020.101476DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7479354PMC
August 2020

Contributions and Limitations of Biophysical Approaches to Study of the Interactions between Amphiphilic Molecules and the Plant Plasma Membrane.

Plants (Basel) 2020 May 20;9(5). Epub 2020 May 20.

Unité de Génie Enzymatique et Cellulaire, UMR 7025 CNRS/UPJV/UTC, Université de Picardie Jules Verne, 80039 Amiens, France.

Some amphiphilic molecules are able to interact with the lipid matrix of plant plasma membranes and trigger the immune response in plants. This original mode of perception is not yet fully understood and biophysical approaches could help to obtain molecular insights. In this review, we focus on such membrane-interacting molecules, and present biophysically grounded methods that are used and are particularly interesting in the investigation of this mode of perception. Rather than going into overly technical details, the aim of this review was to provide to readers with a plant biochemistry background a good overview of how biophysics can help to study molecular interactions between bioactive amphiphilic molecules and plant lipid membranes. In particular, we present the biomimetic membrane models typically used, solid-state nuclear magnetic resonance, molecular modeling, and fluorescence approaches, because they are especially suitable for this field of research. For each technique, we provide a brief description, a few case studies, and the inherent limitations, so non-specialists can gain a good grasp on how they could extend their toolbox and/or could apply new techniques to study amphiphilic bioactive compound and lipid interactions.
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http://dx.doi.org/10.3390/plants9050648DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7285231PMC
May 2020

Linolenic fatty acid hydroperoxide acts as biocide on plant pathogenic bacteria: Biophysical investigation of the mode of action.

Bioorg Chem 2020 07 1;100:103877. Epub 2020 May 1.

Laboratoire de Chimie des Molécules Naturelles (LCMN), Gembloux Agro-Bio Tech, Université de Liège, 2, Passage des Déportés, B-5030 Gembloux, Belgium.

Fatty acid hydroperoxides (HPO) are free phyto-oxylipins known for their crucial role as signalling molecules during plant defense mechanisms. They were also demonstrated to have direct biocidal activities against plant pathogens including gram negative bacteria. In the present work, the biocidal effect of one linolenic fatty acid hydroperoxide, namely 13-HPOT has been investigated on three plant pathogen gram negative bacteria: Pectobacterium carotovorum, Pseudomonas syringae and Xanthomonas translucens. We showed that 13-HPOT has a strong dose response effect on those phytopathogens. In a second part, the molecular mechanism behind the antibacterial effect of 13-HPOT was investigated at a molecular level using an integrative biophysical approach combining in vitro and in silico methods. Since other antimicrobial amphiphilic molecules have been shown to target the lipid membrane of the organisms they act on, we focused our study on the interaction of 13-HPOT with biomimetic membranes. In a first step, we hypothesized that the inner membrane of the bacteria was the main site of action of 13-HPOT and hence we used lipids representative of this membrane to form our models. Our results indicated that 13-HPOT can interact with the lipid representative of the inner bacterial plasma membrane. A strong membrane insertion is suggested but no major permeabilization of the membrane is observed. Phosphatidylethanolamine (PE) and cardiolipin (CL), present in the bacterial plasma membrane, appear to play important roles in this interaction. We suggest that the mode of action of 13-HPOT should involve either subtle changes in membrane properties, such as its lateral organization and distribution, and/or interactions with membrane proteins.
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http://dx.doi.org/10.1016/j.bioorg.2020.103877DOI Listing
July 2020

Enhancing the Membranolytic Activity of Saponins by Fast Microwave Hydrolysis.

Molecules 2020 Apr 9;25(7). Epub 2020 Apr 9.

Organic Synthesis and Mass Spectrometry Laboratory (S²MOs), University of Mons-UMONS, 23 Place du Parc, 7000 Mons; Belgium.

Saponins are plant secondary metabolites. There are associated with defensive roles due to their cytotoxicity and are active against microorganisms. Saponins are frequently targeted to develop efficient drugs. Plant biomass containing saponins deserves sustained interest to develop high-added value applications. A key issue when considering the use of saponins for human healthcare is their toxicity that must be modulated before envisaging any biomedical application. This can only go through understanding the saponin-membrane interactions. Quinoa is abundantly consumed worldwide, but the quinoa husk is discarded due to its astringent taste associated with its saponin content. Here, we focus on the saponins of the quinoa husk extract (QE). We qualitatively and quantitively characterized the QE saponins using mass spectrometry. They are bidesmosidic molecules, with two oligosaccharidic chains appended on the aglycone with two different linkages; a glycosidic bond and an ester function. The latter can be hydrolyzed to prepare monodesmosidic molecules. The microwave-assisted hydrolysis reaction was optimized to produce monodesmosidic saponins. The membranolytic activity of the saponins was assayed based on their hemolytic activity that was shown to be drastically increased upon hydrolysis. In silico investigations confirmed that the monodesmosidic saponins interact preferentially with a model phospholipid bilayer, explaining the measured increased hemolytic activity.
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http://dx.doi.org/10.3390/molecules25071731DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7181122PMC
April 2020

Crude Extract as a Powerful Natural Herbicide and Insight into the Mode of Action of Its Bioactive Molecules.

Biomolecules 2020 01 31;10(2). Epub 2020 Jan 31.

Integrated and Urban Plant Pathology Laboratory, Gembloux Agro-Bio Tech, University of Liège 2, Passage des Déportés, 2 5030 Gembloux, Belgium.

The use of chemical herbicides could not only potentially induce negative impacts on the environment, animals, and human health, but also increase the weed resistance to herbicides. In this context, the use of plant extracts could be an interesting and natural alternative to chemical products. It is important to understand the mode of action of their bioactive compounds. This is why we have studied the herbicidal effect of crude extract in terms of inhibition of weeds' seedling growth and its impact on physiological parameters of treated plantlets, like conductivity, dry weight, and fluorescence, and biochemical parameters linked to oxidative stress. We have observed that crude extract induces oxidative stress in the treated plants and consequently disturbs the physiological and biochemical functions of the plant cells. We have investigated the herbicidal activity of three bioactive compounds, naringenin, myricitrin, and quercetin, from the crude extract. In both pre- and post-emergence trials, naringenin and myricitrin were significantly more phytotoxic than quercetin. We suggest that their differential initial interaction with the plant's plasma membrane could be one of the main signals for electrolyte leakage and production of high levels of phenoxyl radicals.
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http://dx.doi.org/10.3390/biom10020209DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7072411PMC
January 2020

Plant-Pathogen Interactions: Underestimated Roles of Phyto-oxylipins.

Trends Plant Sci 2020 01 23;25(1):22-34. Epub 2019 Oct 23.

Laboratory of Natural Molecules Chemistry (LCMN), Gembloux Agro-Bio Tech, University of Liège, 2, Passage des Déportés, B-5030 Gembloux, Belgium.

Plant (or phyto-) oxylipins (POs) are produced under a wide range of stress conditions and although they are well known to activate stress-related signalling pathways, the nonsignalling roles of POs are poorly understood. We describe oxylipins as direct biocidal agents and propose that structure-function relationships play here a pivotal role. Based on their chemical configuration, POs, such as reactive oxygen and electrophile species, activate defence-related gene expression. We also propose that their ability to interact with pathogen membranes is important, but still misunderstood, and that they are involved in cross-kingdom communication. Taken as a whole, the current literature suggests that POs have a high potential as biocontrol agents. However, the mechanisms underlying these multifaceted compounds remain largely unknown.
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http://dx.doi.org/10.1016/j.tplants.2019.09.009DOI Listing
January 2020

Molecular Model for the Self-Assembly of the Cyclic Lipodepsipeptide Pseudodesmin A.

J Phys Chem B 2019 10 14;123(42):8916-8922. Epub 2019 Oct 14.

Laboratory of Molecular Biophysics at Interfaces, TERRA Research Center, Gembloux Agro-Bio Tech , University of Liège , Passage des déportés 2 , B-5030 Gembloux , Belgium.

Self-assembly of peptides into supramolecular structures represents an active field of research with potential applications ranging from material science to medicine. Their study typically involves the application of a large toolbox of spectroscopic and imaging techniques. However, quite often, the structural aspects remain underexposed. Besides, molecular modeling of the self-assembly process is usually difficult to handle, since a vast conformational space has to be sampled. Here, we have used an approach that combines short molecular dynamics simulations for peptide dimerization and NMR restraints to build a model of the supramolecular structure from the dimeric units. Experimental NMR data notably provide crucial information about the conformation of the monomeric units, the supramolecular assembly dimensions, and the orientation of the individual peptides within the assembly. This / mixed approach enables us to define accurate atomistic models of supramolecular structures of the bacterial cyclic lipodepsipeptide pseudodesmin A.
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http://dx.doi.org/10.1021/acs.jpcb.9b08035DOI Listing
October 2019

Insights into the Relationships Between Herbicide Activities, Molecular Structure and Membrane Interaction of Cinnamon and Citronella Essential Oils Components.

Int J Mol Sci 2019 Aug 16;20(16). Epub 2019 Aug 16.

Molecular Biophysics at Interfaces Laboratory, TERRA Research Centre, GX ABT, Université de Liège, 4000 Liège, Belgium.

Since the 50's, the massive and "environmental naïve" use of synthetic chemistry has revolutionized the farming community facing the dramatic growth of demography. However, nowadays, the controversy grows regarding the long-term harmful effects of these products on human health and the environment. In this context, the use of essential oils (EOs) could be an alternative to chemical products and a better understanding of their mode of biological action for new and optimal applications is of importance. Indeed, if the biocidal effects of some EOs or their components have been at least partly elucidated at the molecular level, very little is currently known regarding their mechanism of action as herbicides at the molecular level. Here, we showed that cinnamon and Java citronella essential oils and some of their main components, i.e.,, cinnamaldehyde (CIN), citronellal (CitA), and citronellol (CitO) could act as efficient herbicides when spread on leaves. The individual EO molecules are small amphiphiles, allowing for them to cross the mesh of cell wall and directly interact with the plant plasma membrane (PPM), which is one of the potential cellular targets of EOs. Hence, we investigated and characterized their interaction with biomimetic PPM while using an integrative biophysical approach. If CitO and CitA, maintaining a similar chemical structure, are able to interact with the model membranes without permeabilizing effect, CIN belonging to the phenylpropanoid family, is not. We suggested that different mechanisms of action for the two types of molecules can occur: while the monoterpenes could disturb the lipid organization and/or domain formation, the phenylpropanoid CIN could interact with membrane receptors.
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http://dx.doi.org/10.3390/ijms20164007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6720526PMC
August 2019

Multiple C2 domains and transmembrane region proteins (MCTPs) tether membranes at plasmodesmata.

EMBO Rep 2019 08 9;20(8):e47182. Epub 2019 Jul 9.

Laboratoire de Biogenèse Membranaire, UMR5200, CNRS, Université de Bordeaux, Villenave d'Ornon, France.

In eukaryotes, membrane contact sites (MCS) allow direct communication between organelles. Plants have evolved a unique type of MCS, inside intercellular pores, the plasmodesmata, where endoplasmic reticulum (ER)-plasma membrane (PM) contacts coincide with regulation of cell-to-cell signalling. The molecular mechanism and function of membrane tethering within plasmodesmata remain unknown. Here, 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 plasmodesmata proteins that insert into the ER via their transmembrane region while their C2 domains dock to the PM through interaction with anionic phospholipids. A Atmctp3/Atmctp4 loss of function mutant induces plant developmental defects, impaired plasmodesmata function and composition, while MCTP4 expression in a yeast Δtether mutant partially restores ER-PM tethering. Our data suggest that MCTPs are unique membrane tethers controlling both ER-PM contacts and cell-to-cell signalling.
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http://dx.doi.org/10.15252/embr.201847182DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6680132PMC
August 2019

Is It Possible to Predict the Odor of a Molecule on the Basis of its Structure?

Int J Mol Sci 2019 Jun 20;20(12). Epub 2019 Jun 20.

Laboratory of Chemistry of Natural Molecules, Gembloux Agro-Bio Tech, University of Liège, 5030 Gembloux, Belgium.

The olfactory sense is the dominant sensory perception for many animals. When Richard Axel and Linda B. Buck received the Nobel Prize in 2004 for discovering the G protein-coupled receptors' role in olfactory cells, they highlighted the importance of olfaction to the scientific community. Several theories have tried to explain how cells are able to distinguish such a wide variety of odorant molecules in a complex context in which enantiomers can result in completely different perceptions and structurally different molecules. Moreover, sex, age, cultural origin, and individual differences contribute to odor perception variations that complicate the picture. In this article, recent advances in olfaction theory are presented, and future trends in human olfaction such as structure-based odor prediction and artificial sniffing are discussed at the frontiers of chemistry, physiology, neurobiology, and machine learning.
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http://dx.doi.org/10.3390/ijms20123018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6627536PMC
June 2019

Triterpenoids in Echinoderms: Fundamental Differences in Diversity and Biosynthetic Pathways.

Mar Drugs 2019 Jun 13;17(6). Epub 2019 Jun 13.

Biology of Marine Organisms and Biomimetics Unit, Research Institute for Biosciences, University of Mons-UMONS, 7000 Mons, Belgium.

Echinoderms form a remarkable phylum of marine invertebrates that present specific chemical signatures unique in the animal kingdom. It is particularly the case for essential triterpenoids that evolved separately in each of the five echinoderm classes. Indeed, while most animals have Δ-sterols, sea cucumbers (Holothuroidea) and sea stars (Asteroidea) also possess Δ and Δ-sterols, a characteristic not shared with brittle stars (Ophiuroidea), sea urchins (Echinoidea), and crinoids (Crinoidea). These particular Δ and Δ sterols emerged as a self-protection against membranolytic saponins that only sea cucumbers and sea stars produce as a defense mechanism. The diversity of saponins is large; several hundred molecules have been described in the two classes of these saponins (i.e., triterpenoid or steroid saponins). This review aims to highlight the diversity of triterpenoids in echinoderms by focusing on sterols and triterpenoid glycosides, but more importantly to provide an updated view of the biosynthesis of these molecules in echinoderms.
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http://dx.doi.org/10.3390/md17060352DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6627624PMC
June 2019

The activity of the saponin ginsenoside Rh2 is enhanced by the interaction with membrane sphingomyelin but depressed by cholesterol.

Sci Rep 2019 05 13;9(1):7285. Epub 2019 May 13.

Université catholique de Louvain, Louvain Drug Research Institute, Cellular & Molecular Pharmacology Unit, 1200, Brussels, Belgium.

The membrane activity of some saponins, such as digitonin or alpha-hederin, is usually attributed to their interaction with membrane cholesterol (Chol). This contrasts with our recent publication showing that Chol, contrary to sphingomyelin (SM), can delay the cytotoxicity of the saponin ginsenoside Rh2, challenging the usual view that most saponins mediate their membrane effects through interaction with Chol. The aim of the present study was to elucidate the respective importance of Chol and SM as compared to phosphatidylcholine (PC) species in the membrane-related effects of Rh2. On simple lipid monolayers, Rh2 interacted more favorably with eggSM and DOPC than with Chol and eggPC. Using Large Unilamellar Vesicles (LUVs) of binary or ternary lipid compositions, we showed that Rh2 increased vesicle size, decreased membrane fluidity and induced membrane permeability with the following preference: eggSM:eggPC > eggSM:eggPC:Chol > eggPC:Chol. On Giant Unilamellar Vesicles (GUVs), we evidenced that Rh2 generated positive curvatures in eggSM-containing GUVs and small buds followed by intra-luminal vesicles in eggSM-free GUVs. Altogether, our data indicate that eggSM promotes and accelerates membrane-related effects induced by Rh2 whereas Chol slows down and depresses these effects. This study reconsiders the theory that Chol is the only responsible for the activity of saponins.
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http://dx.doi.org/10.1038/s41598-019-43674-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6513819PMC
May 2019

Interactions Between Natural Herbicides and Lipid Bilayers Mimicking the Plant Plasma Membrane.

Front Plant Sci 2019 18;10:329. Epub 2019 Mar 18.

TERRA, Laboratory of Molecular Biophysics at Interfaces, Gembloux Agro-Bio Tech, University of Liège, Gembloux, Belgium.

Natural phytotoxic compounds could become an alternative to traditional herbicides in the framework of sustainable agriculture. Nonanoic acid, sarmentine and sorgoleone are such molecules extracted from plants and able to inhibit the growth of various plant species. However, their mode of action is not fully understood and despite clues indicating that they could affect the plant plasma membrane, molecular details of such phenomenon are lacking. In this paper, we investigate the interactions between those natural herbicides and artificial bilayers mimicking the plant plasma membrane. First, their ability to affect lipid order and fluidity is evaluated by means of fluorescence measurements. It appears that sorgoleone has a clear ordering effect on lipid bilayers, while nonanoic acid and sarmentine induce no or little change to these parameters. Then, a thermodynamic characterization of interactions of each compound with lipid vesicles is obtained with isothermal titration calorimetry, and their respective affinity for bilayers is found to be ranked as follows: sorgoleone > sarmentine > nonanoic acid. Finally, molecular dynamics simulations give molecular details about the location of each compound within a lipid bilayer and confirm the rigidifying effect of sorgoleone. Data also suggest that mismatch in alkyl chain length between nonanoic acid or sarmentine and lipid hydrophobic tails could be responsible for bilayer destabilization. Results are discussed regarding their implications for the phytotoxicity of these compounds.
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http://dx.doi.org/10.3389/fpls.2019.00329DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6431664PMC
March 2019

Exploring the Dual Interaction of Natural Rhamnolipids with Plant and Fungal Biomimetic Plasma Membranes through Biophysical Studies.

Int J Mol Sci 2019 Feb 26;20(5). Epub 2019 Feb 26.

Unité de Génie Enzymatique et Cellulaire, CNRS UMR 7025, Université de Picardie Jules Verne (UPJV), 80039 Amiens, France.

Rhamnolipids (RLs) are potential biocontrol agents for crop culture protection. Their mode of action has been proposed as dual, combining plant protection activation and antifungal activities. The present work focuses on the interaction of natural RLs with plant and fungi membrane models at the molecular scale. Representative models were constructed and the interaction with RLs was studied by Fourier transform infrared (FTIR) and deuterium nuclear magnetic resonance (²H NMR) spectroscopic measurements. Molecular dynamic (MD) simulations were performed to investigate RL insertion in lipid bilayers. Our results showed that the RLs fit into the membrane models and were located near the lipid phosphate group of the phospholipid bilayers, nearby phospholipid glycerol backbones. The results obtained with plant plasma membrane models suggest that the insertion of RLs inside the lipid bilayer did not significantly affect lipid dynamics. Oppositely, a clear fluidity increase of fungi membrane models was observed. This effect was related to the presence and the specific structure of ergosterol. The nature of the phytosterols could also influence the RL effect on plant plasma membrane destabilization. Subtle changes in lipid dynamics could then be linked with plant defense induction and the more drastic effects associated with fungal membrane destabilization.
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http://dx.doi.org/10.3390/ijms20051009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6429473PMC
February 2019

Linoleic and linolenic acid hydroperoxides interact differentially with biomimetic plant membranes in a lipid specific manner.

Colloids Surf B Biointerfaces 2019 Mar 7;175:384-391. Epub 2018 Dec 7.

Laboratory of Molecular Biophysics at Interfaces, Gembloux Agro-Bio Tech, University of Liege, 2, Passage des Déportés, B-5030 Gembloux, Belgium.

Linoleic and linolenic acid hydroperoxides (HPOs) constitute key intermediate oxylipins playing an important role as signaling molecules during plant defense processes in response to biotic or abiotic stress. They have also been demonstrated in vitro as antimicrobial agents against plant fungi and bacteria. To reach the phytopathogens in vivo, the HPOs biosynthesized in the plant cells must cross the plant plasma membrane (PPM) where they can also interact with plasma membrane lipids and have an effect on their organization. In the present study, we have investigated the interaction properties of HPOs with PPM at a molecular level using biophysical tools combining in vitro and in silico approaches and using plant biomimetic lipid systems. Our results have shown that HPOs are able to interact with PPM lipids and perturb their lateral organization. Glucosylceramide (GluCer) is a privileged partner, sitosterol lessens their binding and the presence of both GluCer and sitosterol further reduces their interaction. Hydrophobic effect and polar interactions are involved in the binding. The chemical structure of HPOs influences their affinity for PPM lipids. The presence of three double bonds in the HPO molecule gives rise to a higher affinity comparatively to two double bonds, which can be explained by their differential interaction with the lipid polar headgroups.
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http://dx.doi.org/10.1016/j.colsurfb.2018.12.014DOI Listing
March 2019

Insight into the Self-Assembling Properties of Peptergents: A Molecular Dynamics Simulation Study.

Int J Mol Sci 2018 Sep 14;19(9). Epub 2018 Sep 14.

Laboratoire de Biophysique Moléculaire aux Interfaces, Gembloux Agro-Bio Tech, University of Liège, Passage des déportés 2, 5030 Gembloux, Belgium.

By manipulating the various physicochemical properties of amino acids, the design of peptides with specific self-assembling properties has been emerging for more than a decade. In this context, short peptides possessing detergent properties (so-called "peptergents") have been developed to self-assemble into well-ordered nanostructures that can stabilize membrane proteins for crystallization. In this study, the peptide with "peptergency" properties, called ADA8 and extensively described by Tao et al., is studied by molecular dynamic simulations for its self-assembling properties in different conditions. In water, it spontaneously forms beta sheets with a β barrel-like structure. We next simulated the interaction of this peptide with a membrane protein, the bacteriorhodopsin, in the presence or absence of a micelle of dodecylphosphocholine. According to the literature, the peptergent ADA8 is thought to generate a belt of β structures around the hydrophobic helical domain that could help stabilize purified membrane proteins. Molecular dynamic simulations are here used to image this mechanism and provide further molecular details for the replacement of detergent molecules around the protein. In addition, we generalized this behavior by designing an amphipathic peptide with beta propensity, which was called ABZ12. Both peptides are able to surround the membrane protein and displace surfactant molecules. To our best knowledge, this is the first molecular mechanism proposed for "peptergency".
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http://dx.doi.org/10.3390/ijms19092772DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6163580PMC
September 2018

How different sterols contribute to saponin tolerant plasma membranes in sea cucumbers.

Sci Rep 2018 Jul 18;8(1):10845. Epub 2018 Jul 18.

Laboratory of molecular biophysics of interfaces, Gembloux Agro-Bio Tech, University of Liege, B-5030, Gembloux, Belgium.

Sea cucumbers produce saponins as a chemical defense mechanism, however their cells can tolerate the cytotoxic nature of these chemicals. To elucidate the molecular mechanisms behind this tolerance a suite of complementary biophysical tools was used, firstly using liposomes for in vitro techniques then using in silico approaches for a molecular-level insight. The holothuroid saponin Frondoside A, caused significantly less permeabilization in liposomes containing a Δ holothuroid sterol than those containing cholesterol and resulted in endothermic interactions versus exothermic interactions with cholesterol containing liposomes. Lipid phases simulations revealed that Frondoside A has an agglomerating effect on cholesterol domains, however, induced small irregular Δ sterol clusters. Our results suggest that the structural peculiarities of holothuroid sterols provide sea cucumbers with a mechanism to mitigate the sterol-agglomerating effect of saponins, and therefore to protect their cells from the cytotoxicity of the saponins they produce.
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http://dx.doi.org/10.1038/s41598-018-29223-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6052070PMC
July 2018

Interaction between the barley allelochemical compounds gramine and hordenine and artificial lipid bilayers mimicking the plant plasma membrane.

Sci Rep 2018 06 28;8(1):9784. Epub 2018 Jun 28.

Laboratory of Molecular Biophysics at Interfaces, Gembloux Agro-Bio Tech, University of Liège, Gembloux, Belgium.

Some plants affect the development of neighbouring plants by releasing secondary metabolites into their environment. This phenomenon is known as allelopathy and is a potential tool for weed management within the framework of sustainable agriculture. While many studies have investigated the mode of action of various allelochemicals (molecules emitted by allelopathic plants), little attention has been paid to their initial contact with the plant plasma membrane (PPM). In this paper, this key step is explored for two alkaloids, gramine and hordenine, that are allelochemicals from barley. Using in vitro bioassays, we first showed that gramine has a greater toxicity than hordenine towards a weed commonly found in northern countries (Matricaria recutita L.). Then, isothermal titration calorimetry was used to show that these alkaloids spontaneously interact with lipid bilayers that mimic the PPM. The greater impact of gramine on the thermotropic behaviour of lipids compared to hordenine was established by means of infrared spectroscopy. Finally, the molecular mechanisms of these interactions were explored with molecular dynamics simulations. The good correlation between phytotoxicity and the ability to disturb lipid bilayers is discussed. In this study, biophysical tools were used for the first time to investigate the interactions of allelochemicals with artificial PPM.
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http://dx.doi.org/10.1038/s41598-018-28040-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6023908PMC
June 2018

Synthetic Rhamnolipid Bolaforms trigger an innate immune response in Arabidopsis thaliana.

Sci Rep 2018 06 4;8(1):8534. Epub 2018 Jun 4.

RIBP-EA 4707, SFR Condorcet FR CNRS 3417, University of Reims Champagne-Ardenne, Reims, 51100, France.

Stimulation of plant innate immunity by natural and synthetic elicitors is a promising alternative to conventional pesticides for a more sustainable agriculture. Sugar-based bolaamphiphiles are known for their biocompatibility, biodegradability and low toxicity. In this work, we show that Synthetic Rhamnolipid Bolaforms (SRBs) that have been synthesized by green chemistry trigger Arabidopsis innate immunity. Using structure-function analysis, we demonstrate that SRBs, depending on the acyl chain length, differentially activate early and late immunity-related plant defense responses and provide local increase in resistance to plant pathogenic bacteria. Our biophysical data suggest that SRBs can interact with plant biomimetic plasma membrane and open the possibility of a lipid driven process for plant-triggered immunity by SRBs.
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http://dx.doi.org/10.1038/s41598-018-26838-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5986815PMC
June 2018

d-Xylose and l-arabinose laurate esters: Enzymatic synthesis, characterization and physico-chemical properties.

Enzyme Microb Technol 2018 May 4;112:14-21. Epub 2018 Feb 4.

FARE laboratory, Chaire AFERE, Université de Reims-Champagne-Ardenne, INRA, 51686 Reims Cedex, France. Electronic address:

Efficient enzymatic synthesis of d-xylose and l-arabinose lauryl mono- and diesters has been achieved by transesterification reactions catalysed by immobilized Candida antarctica lipase B as biocatalyst, in organic medium in the presence of d-xylose or l-arabinose and vinyllaurate at 50 °C. In case of l-arabinose, one monoester and one diester were obtained in a 57% overall yield. A more complex mixture was produced for d-xylose as two monoesters and two diesters were synthesized in a 74.9% global yield. The structures of all these pentose laurate esters was solved. Results demonstrated that the esterification first occurred regioselectively onto the primary hydroxyl groups. Pentose laurate esters exhibited interesting features such as low critical aggregation concentrations values all inferior to 25 μM. Our study demonstrates that the enzymatic production of l-arabinose and d-xylose-based esters represents an interesting approach for the production of green surfactants from lignocellulosic biomass-derived pentoses.
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http://dx.doi.org/10.1016/j.enzmictec.2018.01.008DOI Listing
May 2018

Eudicot plant-specific sphingolipids determine host selectivity of microbial NLP cytolysins.

Science 2017 12;358(6369):1431-1434

Centre of Plant Molecular Biology, Eberhard-Karls-University Tübingen, Auf der Morgenstelle 32, 72076 Tübingen, Germany.

Necrosis and ethylene-inducing peptide 1-like (NLP) proteins constitute a superfamily of proteins produced by plant pathogenic bacteria, fungi, and oomycetes. Many NLPs are cytotoxins that facilitate microbial infection of eudicot, but not of monocot plants. Here, we report glycosylinositol phosphorylceramide (GIPC) sphingolipids as NLP toxin receptors. Plant mutants with altered GIPC composition were more resistant to NLP toxins. Binding studies and x-ray crystallography showed that NLPs form complexes with terminal monomeric hexose moieties of GIPCs that result in conformational changes within the toxin. Insensitivity to NLP cytolysins of monocot plants may be explained by the length of the GIPC head group and the architecture of the NLP sugar-binding site. We unveil early steps in NLP cytolysin action that determine plant clade-specific toxin selectivity.
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http://dx.doi.org/10.1126/science.aan6874DOI Listing
December 2017

Development of coated liposomes loaded with ghrelin for nose-to-brain delivery for the treatment of cachexia.

Int J Nanomedicine 2017 28;12:8531-8543. Epub 2017 Nov 28.

Laboratoire de Pharmacie Galénique et de Biopharmacie, Université libre de Bruxelles (ULB), Brussels.

The aim of the present study was to develop a ghrelin-containing formulation based on liposomes coated with chitosan intended for nose-brain delivery for the treatment of cachexia. Among the three types of liposomes developed, anionic liposomes provided the best results in terms of encapsulation efficiency (56%) and enzymatic protection against trypsin (20.6% vs 0% for ghrelin alone) and carboxylesterase (81.6% vs 17.2% for ghrelin alone). Ghrelin presented both electrostatic and hydrophobic interactions with the anionic lipid bilayer, as demonstrated by isothermal titration calorimetry. Then, anionic liposomes were coated with -(2-hydroxy) propyl-3-trimethyl ammonium chitosan chloride. The coating involved a size increment from 146.9±2.7 to 194±6.1 nm, for uncoated and coated liposomes, respectively. The ζ-potential was similarly increased from -0.3±1.2 mV to 6±0.4 mV before and after coating, respectively. Chitosan provided mucoadhesion, with an increase in mucin adsorption of 22.9%. Enhancement of permeation through the Calu3 epithelial monolayer was also observed with 10.8% of ghrelin recovered in the basal compartment in comparison to 0% for ghrelin alone. Finally, aerosols generated from two nasal devices (VP3 and SP270) intended for aqueous dispersion were characterized with either coated or uncoated liposomes. Contrarily to the SP270 device, VP3 device showed minor changes between coated and uncoated liposome aerosols, as shown by their median volume diameters of 38.4±5.76 and 37.6±5.74 µm, respectively. Overall, the results obtained in this study show that the developed formulation delivered by the VP3 device can be considered as a potential candidate for nose-brain delivery of ghrelin.
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http://dx.doi.org/10.2147/IJN.S147650DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5713684PMC
March 2018

Could saponins be used to enhance bioremediation of polycyclic aromatic hydrocarbons in aged-contaminated soils?

Chemosphere 2018 Mar 1;194:414-421. Epub 2017 Dec 1.

AGROBIOCHEM Department, General and Organic Chemistry, University of Liège, Gembloux Agro-Bio Tech, 2 Passage des Déportés, 5030 Gembloux, Belgium. Electronic address:

Polycyclic aromatic hydrocarbons (PAH) are persistent organic compounds of major concern that tend to accumulate in the environment, threatening ecosystems and health. Brownfields represent an important tank for PAHs and require remediation. Researches to develop bioremediation and phytoremediation techniques are being conducted as alternatives to environmentally aggressive, expensive and often disruptive soil remediation strategies. The objectives of the present study were to investigate the potential of saponins (natural surfactants) as extracting agents and as bioremediation enhancers on an aged-contaminated soil. Two experiments were conducted on a brownfield soil containing 15 PAHs. In a first experiment, soil samples were extracted with saponins solutions (0; 1; 2; 4 and 8 g.L). In a second experiment conducted in microcosms (28 °C), soil samples were incubated for 14 or 28 days in presence of saponins (0; 2.5 and 5 mg g). CO emissions were monitored throughout the experiment. After the incubation, dehydrogenase activity was measured as an indicator of microbiological activity and residual PAHs were determined. In both experiments PAHs were determined using High-Performance Liquid Chromatography and Fluorimetric Detection. The 4 g.L saponins solution extracted significantly more acenaphtene, fluorene, phenanthrene, anthracene, and pyrene than water. PAHs remediation was not enhanced in presence of saponins compared to control samples after 28 days. However CO emissions and dehydrogenase activities were significantly more important in presence of saponins, suggesting no toxic effect of these surfactants towards soil microbiota.
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http://dx.doi.org/10.1016/j.chemosphere.2017.11.174DOI Listing
March 2018

Structural basis for plant plasma membrane protein dynamics and organization into functional nanodomains.

Elife 2017 07 31;6. Epub 2017 Jul 31.

Laboratoire de Biogenèse Membranaire (LBM), Unité Mixte de Recherche UMR 5200, CNRS, Université de Bordeaux, Bordeaux, France.

Plasma Membrane is the primary structure for adjusting to ever changing conditions. PM sub-compartmentalization in domains is thought to orchestrate signaling. Yet, mechanisms governing membrane organization are mostly uncharacterized. The plant-specific REMORINs are proteins regulating hormonal crosstalk and host invasion. REMs are the best-characterized nanodomain markers via an uncharacterized moiety called REMORIN C-terminal Anchor. By coupling biophysical methods, super-resolution microscopy and physiology, we decipher an original mechanism regulating the dynamic and organization of nanodomains. We showed that targeting of REMORIN is independent of the COP-II-dependent secretory pathway and mediated by PI4P and sterol. REM-CA is an unconventional lipid-binding motif that confers nanodomain organization. Analyses of REM-CA mutants by single particle tracking demonstrate that mobility and supramolecular organization are critical for immunity. This study provides a unique mechanistic insight into how the tight control of spatial segregation is critical in the definition of PM domain necessary to support biological function.
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http://dx.doi.org/10.7554/eLife.26404DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5536944PMC
July 2017

Differential Interaction of Synthetic Glycolipids with Biomimetic Plasma Membrane Lipids Correlates with the Plant Biological Response.

Langmuir 2017 09 5;33(38):9979-9987. Epub 2017 Sep 5.

Unité de Génie Enzymatique et Cellulaire, FRE CNRS 3580, Structure Fédérative de Recherche Condorcet, Université de Picardie Jules Verne , 33 Rue Saint-Leu, F-80039 Amiens, France.

Natural and synthetic amphiphilic molecules including lipopeptides, lipopolysaccharides, and glycolipids are able to induce defense mechanisms in plants. In the present work, the perception of two synthetic C14 rhamnolipids, namely, Alk-RL and Ac-RL, differing only at the level of the lipid tail terminal group have been investigated using biological and biophysical approaches. We showed that Alk-RL induces a stronger early signaling response in tobacco cell suspensions than does Ac-RL. The interactions of both synthetic RLs with simplified biomimetic membranes were further analyzed using experimental and in silico approaches. Our results indicate that the interactions of Alk-RL and Ac-RL with lipids were different in terms of insertion and molecular responses and were dependent on the lipid composition of model membranes. A more favorable insertion of Alk-RL than Ac-RL into lipid membranes is observed. Alk-RL forms more stable molecular assemblies than Ac-RL with phospholipids and sterols. At the molecular level, the presence of sterols tends to increase the RLs' interaction with lipid bilayers, with a fluidizing effect on the alkyl chains. Taken together, our findings suggest that the perception of these synthetic RLs at the membrane level could be related to a lipid-driven process depending on the organization of the membrane and the orientation of the RLs within the membrane and is correlated with the induction of early signaling responses in tobacco cells.
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http://dx.doi.org/10.1021/acs.langmuir.7b01264DOI Listing
September 2017

Changes in membrane biophysical properties induced by the Budesonide/Hydroxypropyl-β-cyclodextrin complex.

Biochim Biophys Acta Biomembr 2017 Oct 20;1859(10):1930-1940. Epub 2017 Jun 20.

Université catholique de Louvain, Louvain Drug Research Institute, Cellular and Molecular Pharmacology Unit, Avenue E. Mounier 73, B1.73.05, B-1200 Bruxelles, Belgium. Electronic address:

Budesonide (BUD), a poorly soluble anti-inflammatory drug, is used to treat patients suffering from asthma and COPD (Chronic Obstructive Pulmonary Disease). Hydroxypropyl-β-cyclodextrin (HPβCD), a biocompatible cyclodextrin known to interact with cholesterol, is used as a drug-solubilizing agent in pharmaceutical formulations. Budesonide administered as an inclusion complex within HPβCD (BUD:HPβCD) required a quarter of the nominal dose of the suspension formulation and significantly reduced neutrophil-induced inflammation in a COPD mouse model exceeding the effect of each molecule administered individually. This suggests the role of lipid domains enriched in cholesterol for inflammatory signaling activation. In this context, we investigated the effect of BUD:HPβCD on the biophysical properties of membrane lipids. On cellular models (A549, lung epithelial cells), BUD:HPβCD extracted cholesterol similarly to HPβCD. On large unilamellar vesicles (LUVs), by using the fluorescent probes diphenylhexatriene (DPH) and calcein, we demonstrated an increase in membrane fluidity and permeability induced by BUD:HPβCD in vesicles containing cholesterol. On giant unilamellar vesicles (GUVs) and lipid monolayers, BUD:HPβCD induced the disruption of cholesterol-enriched raft-like liquid ordered domains as well as changes in lipid packing and lipid desorption from the cholesterol monolayers, respectively. Except for membrane fluidity, all these effects were enhanced when HPβCD was complexed with budesonide as compared with HPβCD. Since cholesterol-enriched domains have been linked to membrane signaling including pathways involved in inflammation processes, we hypothesized the effects of BUD:HPβCD could be partly mediated by changes in the biophysical properties of cholesterol-enriched domains.
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http://dx.doi.org/10.1016/j.bbamem.2017.06.010DOI Listing
October 2017