Antimicrobial activities of key intermediate plant oxylipins

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.