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

Abstract

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