Rhamnolipids Elicit Plant Defence Responses and Enhance Resistance against Botrytis cinerea

Rhamnolipids (RLs) are amphiphilic secondary metabolites produced by bacteria. They are involved in biofilm formation, swarming motility, hydrocarbon uptake and are also known as virulent factors. Because they are potentially at the plant cells-bacteria interface, we investigated their role as MAMP (Microbe-Associated Molecular Pattern). The effect of RLs was assessed in grapevine. In this plant, RLs induce the expression of a wide range of defence genes. RLs efficiently protect grapevine leaves and berries against the necrotrophic pathogen Botrytis cinerea. In addition to the activation of plant defence responses, RLs displayed antifungal activities against B. cinerea. RLs are well known as biosurfactants in the industry. They are used for a wide range of applications, especially in food, cosmetic and pharmaceutical formulations as well as in bioremediation of pollutants. Because they have both, elicitor and direct antifungal properties, RLs have the potential to be part of alternative strategies in order to reduce the use of pesticides.