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

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.ARC-FIELD project 13/17-1

Mechanosensing and Sphingolipid-Docking Mediate Lipopeptide-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 inArabidopsis thalianaby 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 necrotrophB. cinereabut is distinct from host pattern recognition receptor-mediated immune activation and reminiscent of damage-induced plant immunity

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La mycosubtiline est un lipopeptide antimicrobien, produit par différentes souches de Bacillus subtilis et doté de propriétés hémolytiques et antifongiques. Ses activités biologiques sont dues à des interactions avec les membranes plasmiques des cellules cibles. Cependant, les mécanismes moléculaires exacts de ces interactions doivent être approfondis. Le but de ce travail est de déterminer les éléments structuraux importants qui sont impliqués dans l'activité biologique de la mycosubtiline. A cet effet, nous avons utilisé les systèmes biomimétiques membranaires, comme les monocouches de Langmuir ou les multicouches, et nous avons analysé les interactions de la mycosubtiline avec ceux-ci grâce à des outils biophysiques adaptés (tensiométrie de surface, PM-IRRAS, BAM, SHG, FT-IR, RMN). Nous avons démontré qu'il existe une interaction privilégiée du lipopeptide avec les membranes biomimétiques contenant du stérol. Ainsi le résidu tyrosyle de la mycosubtiline et la fonction alcool secondaire des stérols sont impliqués lors de ces interactions. Des modifications importantes de la morphologie de membranes biomimétiques induites par le lipopeptide ont été mises en évidence ; celles-ci sont plus marquées lorsque le système est ternaire, c'est-à dire quand il contient un glycérophospholipide, un stérol et de la sphingomyélineMycosubtilin is an antimicrobial lipopeptide, produced by different strains of Bacillus subtilis and possessing hemolytic and antifungal properties. Its biological activities are due to its interactions with the plasma membranes of the target cells. However, the precise molecular mechanisms of these interactions need to be further elucidated. The aim of this work is to determine the structure elements involved in the biological activities of mycosubtilin. For that purpose, we used membrane biomimetic systems, such as Langmuir monolayers or multilayers, and we analyzed the interactions of mycosubtilin with them by applying specific biophysical tools (surface tensiometry, PM-IRRAS, BAM, SHG, FT-IR and RMN). We determined that there is a preferential interaction of the lipopeptide with biomimetic membranes containing sterols. Thus the tyrosyle residue of mycosubtilin and the secondary alcohol group of the sterol are involved in these interactions. Significant changes in the morphology of the biomimetic membranes induced by the lipopeptide were highlighted; these modifications are more pronounced when the system is ternary, i.e. when it contains a glycerophospholipid, a sterol and sphingomyeli

Using spectroscopical techniques to understand membrane-molecule interactions

De nombreux processus biochimiques impliquent une interaction entre la membrane plasmique et une molécule agissant sur celle-ci. Les peptides antimicrobiens constituent un bel exemple pour les molécules actives sur la membrane. Notre but est de comprendre les interactions de ces peptides avec la membrane plasmique de leurs cellules cibles. En raison de la complexité de la membrane rendant difficile la compréhension de ces processus, nous avons recours à des systèmes plus simples appelée modèles membranaires. Les modèles membranaires sont donc analysés en absence et en présence des peptides antimicrobiens par différentes techniques spectroscopiques afin d’obtenir des informations à l’échelle moléculaire. La présentation revisite ces techniques d’analyse en mettant en évidence leurs potentialité