Regulation of plant leaf cuticula water dynamics by Rhamnolipids and essential oils

FANANI, MARÍA LAURA; KOURDOVA, LUCILLE TIHOMIROVA; MOTTOLA, MILAGRO; CABADAS, MANUEL ; LASCANO, RAMIRO ; AMBROGGIO, ERNESTO; FABRO, GEORGINA

Córdoba

Congreso; LI Congreso Sociedad Argentina de Biofísica; 2023

Natural Rhamnolipids (RL) are biosurfactants that emerged as promising bioprotectants capable of inducing plant resistance against diverse pathogens. We recently developed RL-stabilized oil-in-water nanoemulsions (NEs)1 for transporting essential oils (EOs) with antimicrobial and pesticidal properties for being applied as bioprotectants over plant leaves. Our studies reveal that both RL suspensions and NEs induce plant resistance against bacterial pathogens. The mechanism by which this induction is stimulated is unknown. Most research focuses on the action of RLs on plant plasma membrane. However, no receptor for RLs in plant cells has been found so far.2 On the other hand, an alteration of the waxy cuticle that protects plant leaves from the environment can trigger plant defense responses.3 We hypothesized that RLs and EOs should first cross the hydrophobic barrier of the plant leaf´s cuticle in order to reach the plant plasma membrane. Here, we adapted a microscopy technique4 to evaluate the structure and water dynamic of Arabidopsis thaliana leaves cuticle before and after treatment with RLs and NEs. Our results indicates that the hydrophobic probe LAURDAN can partition into the cuticle as well as the cell walls and plasma membrane of epidermal cells. The generalized polarization (GP) of LAURDAN in confocal microscopy images indicates that the cell walls and cuticle show a more restricted dynamic for the water molecules (GP 0.4-0.6) in comparison with the interior of the epidermal cells (GP ~0.2). Interestingly, both the GP and the labeled fluorescent area occupied by the cuticle and cell wall are altered by the pre-treatment with NEs or RLs. This may evidence a mechanism related to permeation enhancement by changing the biophysical properties of the external layers of the plant leaves. This effect may enhance foliar penetration and also alter cuticle homeostasis.5 This study may contributing to explain the effectiveness of NEs as triggers of plan defenses.1