Design of rhamnolipids-stabilized nanoemulsions and evaluation of their potential as enhancers of plant defense responses

KOURDOVA, LUCILLE TIHOMIROVA; MOTTOLA, MILAGRO; BOGINO, MARÍA FLORENCIA; MARITANO, PAULA; PEPPINO-MARGUTTI, MICAELA; FANANI, MARÍA LAURA; FABRO, GEORGINA

Ciudad autónoma de Buenos Aires

Simposio; Simposio Frontiers in Bioscience 4; 2023

Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA), en conjunto con la Sociedad Max Planck.

Chemical pesticides used to protect crops result in environmental contamination and the development of resistant strains of pathogens. Therefore, it is necessary to develop new products that can control pests without harming the environment or endangering public health. One approach to enhance plant defenses is the pre-induction of their innate immune system, which leads to the creation of an immune memory known as priming. Rhamnolipids (RLs), produced by certain microorganisms, possess antibacterial and antifungal properties. Natural RLs are effective emulsifiers, enabling the encapsulation of bioactive hydrophobic compounds like essential oils (EOs), which have known antimicrobial and insecticidal properties. In this study, we created nanoemulsions of RLs and EOs, combining their properties, and evaluated their ability to activate the defense mechanisms of Arabidopsis thaliana against the bacterial pathogen Pseudomonas syringae (Pst). We examined in vitro and in planta bacterial growth as well as the induction of plant defense marker genes in leaves pre-treated with nanoemulsions containing RLs and n-hexadecane (HD), an inert oil. These nanoemulsions acted as stimulants for the plant immune system, enhancing its response to the bacterial infection. Analysis of plant defense marker genes suggests that the pre-activation of the salicylic acid pathway, mediated by the nanoemulsions, contributes to enhanced plant defenses. Initial findings suggest that RLs + EOs also reduce in planta growth of Pst, exhibiting greater efficacy than RLs + HD in combating the infection, while not significantly affecting pathogen growth in vitro. Furthermore, microbial growth assays designed to assess the potential toxicity of the nanoemulsions on soil microbiota and beneficial microorganisms used in agriculture, indicated that nanoemulsions of RLs + HD and RLs + EOs are harmless to these communities. Additionally, we will present results on the insecticidal effects of RLs + EOs against the aphid Myzus persicae.