AUTHOR=Trdá Lucie , Janda Martin , Macková Denisa , Pospíchalová Romana , Dobrev Petre I. , Burketová Lenka , Matušinsky Pavel 

TITLE=Dual Mode of the Saponin Aescin in Plant Protection: Antifungal Agent and Plant Defense Elicitor

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 10 - 2019

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.01448

DOI=10.3389/fpls.2019.01448

ISSN=1664-462X

ABSTRACT=<p>Being natural plant antimicrobials, saponins have potential for use as biopesticides. Nevertheless, their activity in plant–pathogen interaction is poorly understood. We performed a comparative study of saponins' antifungal activities on important crop pathogens based on their effective dose (EC<sub>50</sub>) values. Among those saponins tested, aescin showed itself to be the strongest antifungal agent. The antifungal effect of aescin could be reversed by ergosterol, thus suggesting that aescin interferes with fungal sterols. We tested the effect of aescin on plant–pathogen interaction in two different pathosystems: <italic>Brassica napus</italic> versus (fungus) <italic>Leptosphaeria maculans</italic> and <italic>Arabidopsis thaliana</italic> versus (bacterium) <italic>Pseudomonas syringae</italic> pv <italic>tomato</italic> DC3000 (<italic>Pst</italic> DC3000). We analyzed resistance assays, defense gene transcription, phytohormonal production, and reactive oxygen species production. Aescin activated <italic>B. napus</italic> defense through induction of the salicylic acid pathway and oxidative burst. This defense response led finally to highly efficient plant protection against <italic>L. maculans</italic> that was comparable to the effect of fungicides. Aescin also inhibited colonization of <italic>A. thaliana</italic> by <italic>Pst</italic> DC3000, the effect being based on active elicitation of salicylic acid (SA)-dependent immune mechanisms and without any direct antibacterial effect detected. Therefore, this study brings the first report on the ability of saponins to trigger plant immune responses. Taken together, aescin in addition to its antifungal properties activates plant immunity in two different plant species and provides SA-dependent resistance against both fungal and bacterial pathogens.</p>