Synthetic Rhamnolipid Bolaforms trigger an innate immune response in Arabidopsis thaliana

Abstract

Stimulation of plant innate immunity by natural and synthetic elicitors is a promising alternative to conventional pesticides for a more sustainable agriculture. Sugar-based bolaamphiphiles are known for their biocompatibility, biodegradability and low toxicity. In this work, we show that Synthetic Rhamnolipid Bolaforms (SRBs) that have been synthesized by green chemistry trigger Arabidopsis innate immunity. Using structure-function analysis, we demonstrate that SRBs, depending on the acyl chain length, differentially activate early and late immunity-related plant defense responses and provide local increase in resistance to plant pathogenic bacteria. Our biophysical data suggest that SRBs can interact with plant biomimetic plasma membrane and open the possibility of a lipid driven process for plant-triggered immunity by SRBs.

Recent Advances in Synthetic Chemical Inducers of Plant Immunity

“…The bolaamphiphiles surfactants contains a long hydrophobic spacer connecting two hydrophilic moieties. Luzuriaga-Loaiza et al (2018) synthesized rhamnolipid bolaforms (SRBs) and tested their immune induction activity. Depending on the acyl chain length, SRBs differentially induce defense responses and confer local resistance in Arabidopsis against the hemibiotrophic bacteria Pseudomonas syringae but not the necrotrophic fungal pathogen Botrytis cinerea .…”

“…Manual inspection can only process a handful of immune elicitors for recognition of potentially critical bioactive substructures and patterns of known immune inducers ( He et al, 2017 ; Luzuriaga-Loaiza et al, 2018 ). Advances in high-performance computing have made it possible to screen tens of thousands of lead-like molecules computationally.…”

Apoplastic invasion patterns triggering plant immunity: plasma membrane sensing at the frontline

“…Indeed, several molecules such as necrosis and ethylene‐inducing peptide 1‐like (NLP) proteins, harpins, rhamnolipids and lipopeptides trigger plant immunity through lipid receptors and/or potential membrane lipid‐raft structure perturbations (Farace et al , ; Henry et al , ; Klemptner et al , ; Sanchez et al , ). Moreover, several synthetic compounds that mimic IP‐triggered plant signalling or perception are known to interact with biological or biomimetic lipid‐based membranes and trigger plant immunity (Bektas and Eulgem, ; Luzuriaga‐Loaiza et al , ; Nasir et al , ).…”

“…Interestingly, synthetic molecules derived from the RL structure are also known to induce plant immunity. Synthetic rhamnolipid bolaforms (SRBs), composed of two rhamnoses separated by a fatty acid chain (Obounou Akong et al ., ), trigger an immune response in Arabidopsis that varies according to fatty acid chain length (Luzuriaga‐Loaiza et al , ). Ac‐RLs and Alk‐RLs, only differing from natural RLs by the terminal group of the carbon chain (with a methyl for Alk‐RLs and a carboxylic acid for Ac‐RLs), induce ROS production in Arabidopsis (Nasir et al , ).…”

“…Ac‐RLs and Alk‐RLs, only differing from natural RLs by the terminal group of the carbon chain (with a methyl for Alk‐RLs and a carboxylic acid for Ac‐RLs), induce ROS production in Arabidopsis (Nasir et al , ). Interestingly, these synthetic RLs are able to interact with membrane lipids, suggesting that perception of these molecules could involve a lipid‐driven process (Luzuriaga‐Loaiza et al , ; Nasir et al , ). Alk‐RLs were more favourably inserted into model membranes and induced a higher response than Ac‐RL, suggesting that differences in the biological activity of these molecules could be linked to their amphiphilic nature and their capacity to interact with the membrane (Nasir et al , ).…”