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

Analyse des interactions des hydroperoxydes d'acydes gras avec des membranes biomimétiques par des approches biophysiques complémentaires

In the actual context, biopesticides have emerged as a main alternative to conventional agriculture1. Hence, elicitors are metabolites naturally produced by microorganisms, pathogenic or not, and plants which are able to induce the natural resistance of plants. Also, they have proved to be excellent candidates for biological control. In this context, the lipoxygenase pathway leads to the formation of fatty acid degradation products, called oxylipins, which appear to be crucial agents in plant defence mechanisms2,3. Moreover, with their broad spectrum of action and their possible inducibility, oxylipins appear to be promising candidates for their use as elicitors4. This work focuses on two hydroperoxy-derived oxylipins, the 13(S)-hydroperoxy-octadecadienoic acid (13-HPOD) and the 13(S)-hydroperoxy-octadecatrienoic acid (13-HPOT). The study of the interaction of such compounds with representative plant plasma membrane lipids is essential to understand plant resistance mechanisms. Several in silico and experimental techniques of biophysics showed that acyl-hydroperoxides have significant adsorption capacity and a strong affinity for model membranes. They may also penetrate biological membrane but no permeabilisation effect was observed in this work. Slight conformational differences seem to have a significant impact on their ability to interact with plant plasma membranes. Based on these results, further investigation of the interactions of fatty acids hydroperoxides, even more on the 9-forms, with plant plasma membranes and eventually in the presence of phytopathogenic species, would allow a better understanding of the innate immunity and, on the longer term, could lead to the development of new elicitors with biological mechanisms potentially independent of membrane protein receptors.Relation entre l'activité membranaire des hydroperoxydes d'acides gras et leurs activités biologiques en tant que biopesticide

Activité antimicrobienne des oxylipines végétales clés

Nowadays, biopesticides have emerged as a main alternative to conventional agriculture. In this context, plant oxylipins, a vast and diverse family of secondary metabolites originated from polyunsaturated fatty acids (PUFAs), appear to be crucial agents in plant defense mechanisms. Among plant oxylipins, the 13-hydroperoxy oxylipins (13-HPO) constitute key intermediate oxylipins (KIOs) as they can be converted into jasmonic acid, OPDA, dn-OPDA or traumatic acid, well-characterized components involved in plant resistance mechanisms. Their presumed functions include direct antimicrobial effect, stimulation of plant defense gene expression, and/or regulation of plant cell death. However, the precise contribution of each KIOs to plant defense remains essentially unknown. In this work, we focus on two h13-HPO, the 13(S)-hydroperoxy-octadecadienoic acid (13-HPOD) and the 13(S)-hydroperoxy-octadecatrienoic acid (13-HPOT). In vitro growth inhibition assays were performed to investigate the direct antimicrobial activities against 7 pathogens of agronomic interest including bacteria, oomycetes and fungi. This study showed unambiguously that 13-HPO are able to hinder growth of some plant microbial pathogens, generally with a higher efficacity for 13-HPOT. In order to get a better insight into their mechanism of action, a complementary in silico and experimental biophysical approach was applied. Biomimetic pathogen plasma membranes are used to study the mechanism at the molecular level. Slight conformational differences may have significant impacts on their ability to interact with pathogens lipids and plasma membranes.Relations entre l’activité membranaire des hydroperoxydes d’acides gras et leurs activités biologiques en tant que biopesticide

Oxylipins are involved in plant protections processes and are potential biocontrol agents

Nowadays, biopesticides have emerged as a main alternative to conventional agriculture. In this context, plant oxylipins, a vast and diverse family of secondary metabolites originated from polyunsaturated fatty acids (PUFAs), appear to be crucial agents in plant defence mechanisms. Among plant oxylipins, the 13-hydroperoxy oxylipins (13-HPO) constitute key intermediate oxylipins (KIOs) as they can be converted into jasmonic acid, OPDA, dn-OPDA or traumatic acid, well-characterized components involved in plant resistance mechanisms [1][2]. Their presumed functions include direct antimicrobial effect, stimulation of plant defence gene expression, and/or regulation of plant cell death [3]. Otherwise, OPDA and dn-OPDA were also found esterified in more complex structures such as galactolipids. Those compounds are called arabidopsides. However, the precise contribution of each of those molecules in plant defence remains unknown. The first part of this study aims to understand the oxylipins action mechanisms and especially their membrane activities. As arabidopsides are produced under stress and localized at the chloroplast membranes, their interactions with those were studied using biomimetic membranes via a complementary in silico informatics and in vitro biophysical approaches. On the other hand, as KIOs are found in the literature to be potential biocontrol agents, there effect on different pathogens of agronomic interest were studied in vitro, by the same approach. As far as arabidopsides are concerned, results show that they possess different interfacial properties compared to major chloroplast lipids, which they are produced from. Arabidopsides modify the fluidity and permeabilize chloroplast membranes. As chloroplast membrane lipid composition is essential to its photosynthetic ability, such changes in its composition under stress will affect its function. Concerning KIOs, they seem to interact with pathogens plasma membranes. Indeed, in vitro assays show that KIOs can hinder growth of some plant microbial pathogens, with differences between strains and KIOs forms.Les hydroperoxydes d'acides gras, relation structure-fonctio

Nouveauté sur les rôles des oxylipines libres, un potentiel pour les agents de biocontrôle

Nowadays, biopesticides have emerged as a main alternative to conventional agriculture. In this context, plant oxylipins, a vast and diverse family of secondary metabolites originated from polyunsaturated fatty acids (PUFAs), appear to be crucial agents in plant defence mechanisms. Actually, it is highly known that plant oxylipins are produced under a wide range of stress conditions. While those molecules are well known to activate several signalling pathways and to induce adaptations in plant exposed to (a)biotic stresses, non-signalling roles of phyto-oxylipins are poorly understood. Among plant oxylipins, the 13-hydroperoxy oxylipins (13-HPO) constitute key intermediate oxylipins (KIOs) as they can be converted into jasmonic acid, OPDA, dn-OPDA or traumatic acid, well-characterized components involved in plant resistance mechanisms. Their presumed functions include direct antimicrobial effect, stimulation of plant defence gene expression, and/or regulation of plant cell death. However, the precise contribution of each of those molecules in plant defence remains unknown. In this study, 13-HPO properties as direct biocidal agents are investigated. In vitro assays have showed that KIOs can hinder growth of some plant microbial pathogens, with differences between strains and KIOs forms. Further investigation are needed to know if they maintain this power while being exogenously applied on plants, before or after infection. Afterwards, this study aims to understand the oxylipins action mechanisms and especially their membrane activities. As KIOs are found to be potential biocontrol agents and also to interact with plant plasma membranes, their interactions with plants and pathogens plasma membranes were studied using biomimetic membranes via a complementary in silico informatics and in vitro biophysical approaches. Finally, in analogy with other amphiphilic molecules (e.g. surfactins), KIOs may act as elicitors. This hypothesis is reinforced by preliminary results showing the production of reactive oxygen species (priming agents of eliciting reaction) when tobacco roots were in presence of KIOs. Further investigation are needed to confirm this property

The Omnipresence of DYRK1A in Human Diseases

The increasing population will challenge healthcare, particularly because the worldwide population has never been older. Therapeutic solutions to age-related disease will be increasingly critical. Kinases are key regulators of human health and represent promising therapeutic targets for novel drug candidates. The dual-specificity tyrosine-regulated kinase (DYRKs) family is of particular interest and, among them, DYRK1A has been implicated ubiquitously in varied human diseases. Herein, we focus on the characteristics of DYRK1A, its regulation and functional role in different human diseases, which leads us to an overview of future research on this protein of promising therapeutic potential

De nouvelles perspectives sur les rôles des phyto-oxylipines libres, un potentiel pour les agents de lutte biologique

Nowadays, biopesticides have emerged as a main alternative to conventional agriculture. In this context, plant oxylipins, a vast and diverse family of secondary metabolites originated from polyunsaturated fatty acids (PUFAs), appear to be crucial agents in plant defence mechanisms. Actually, it is highly known that plant oxylipins are produced under a wide range of stress conditions. While those molecules are well known to activate several signalling pathways and to induce adaptations in plant exposed to (a)biotic stresses, non-signalling roles of phyto-oxylipins are poorly understood. Among plant oxylipins, the 13-hydroperoxy oxylipins (13-HPO) constitute key intermediate oxylipins (KIOs) as they can be converted into jasmonic acid, OPDA, dn-OPDA or traumatic acid, well-characterized components involved in plant resistance mechanisms [1][2]. Their presumed functions include direct antimicrobial effect, stimulation of plant defence gene expression, and/or regulation of plant cell death [3]. However, the precise contribution of each of those molecules in plant defence remains unknown. In this study, 13-HPO properties as direct biocidal agents are investigated. In vitro assays have showed that KIOs can hinder growth of some plant microbial pathogens, with differences between strains and KIOs forms. Further investigation are needed to know if they maintain this power while being exogenously applied on plants, before or after infection. Afterwards, this study aims to understand the oxylipins action mechanisms and especially their membrane activities. As KIOs are found to be potential biocontrol agents and also to interact with plant plasma membranes [4], their interactions with plants and pathogens plasma membranes were studied using biomimetic membranes via a complementary in silico informatics and in vitro biophysical approaches. Finally, in analogy with other amphiphilic molecules (e.g. surfactins), KIOs may act as elicitors. This hypothesis is reinforced by preliminary results showing the production of reactive oxygen species (priming agents of eliciting reaction) when tobacco roots were in presence of KIOs. Further investigation are needed to confirm this property

Utilisation d'approches biophysiques complémentaires pour étudier les interactions des hydroperoxydes d'acides gras avec les membranes plasmiques des plantes biomimétiques

"Use of complementary biophysical approaches to study the interactions of fatty acid hydroperoxides with biomimetic plant plasma membranes »: poster presented at the annual meeting day of the EDT CHI