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

LUCILE KOURDOVA; MILAGRO MOTTOLA; FLORENCIA BOGINO; MICAELA PEPPINO MARGUTTI; MARIA L. FANANI; GEORGINA FABRO

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

The use of chemical pesticides to protect crop plants may cause environmental contamination and contribute to generate resistant pathogens’ strains. Thus, new products that allow pests’ control without being harmful to the environment or endangering public health, should be developed. One of the strategies currently employed to enhance plant defenses is to pre-induce their innate immune system, conducing to the generation of an immune memory called priming. Rhamnolipids (RLs) produced by some microorganisms, have a wide range of antibacterial and antifungal properties. In addition, natural RLs are excellent emulsifiers, allowing encapsulation of bioactive hydrophobic compounds such as essential oils (EOs) that can act as insect deterrents. Here, we designed nanoemulsions of RLs and EOs, combining the properties of both components, and evaluated their ability to trigger the defenses of the model plant Arabidopsis thaliana against the bacterial pathogen Pseudomonas syringae pv tomato DC3000 (Pst). In vitro and in planta bacterial growth as well induction of plant defense marker genes, were analyzed in plants pre-treated with the nanoemulsions. In addition, in vitro microbial growth assays were performed evaluating the potential toxicity of the nanoemulsions over soil microbiota and on microbia usually formulated in bioinoculants. Nanoemulsions consisting of RLs and n-hexadecane (HD), an inert oil, acted as stimulants of the plant immune system, improving its response to the bacterial infection. These nanoemulsions were innocuous to the natural soil microbiota and to different beneficial microorganisms used in agriculture. Preliminary results indicate that RLs + EOs also decrease the growth in planta of Pst and have higher capacity than RLs + HD to combat the infection, without significantly affecting pathogen growth in vitro. Results involving the effect of RLs + EOs on insects (Myzus persicae) feeding in planta and reproduction will be presented.