Rhamnolipids From Pseudomonas aeruginosa Are Elicitors Triggering Brassica napus Protection Against Botrytis cinerea Without Physiological Disorders

Abstract

Rhamnolipids (RLs) are amphiphilic molecules naturally produced by some bacteria with a large range of biological activities. Although some studies report their potential interest in plant protection, evaluation of their effects and efficiency on annual crops of worldwide agronomic interest is lacking. The main objective of this work was to investigate their elicitor and protective activities on rapeseed crop species while evaluating their physiological effects. Here we report that RLs from Pseudomonas aeruginosa secretome trigger an effective protection of Brassica napus foliar tissues toward the fungus Botrytis cinerea involving the combination of plant defense activation and direct antimicrobial properties. We demonstrated their ability to activate canonical B. napus defense responses including reactive oxygen species production, expression of defense genes, along with callose deposits and stomatal closure as efficient physical protections. In addition, microscopic cell death observations and electrolyte leakage measurements indicated that RLs trigger a hypersensitive response-like defense in this plant. We also showed that foliar spray applications of RLs do not induce deleterious physiological consequences on plant growth or chlorophyll content and that RL protective properties are efficient on several grown cultivars of rapeseed. To our knowledge, this is the first report of RLs as an elicitor that suppresses fungal disease on tissues of an annual crop species under greenhouse conditions. Our results highlight the dual mode of action of these molecules exhibiting plant protection activation and antifungal activities and demonstrate their potential for crop cultures as environmental-friendly biocontrol solution.

Synthetic Mono-Rhamnolipids Display Direct Antifungal Effects and Trigger an Innate Immune Response in Tomato against Botrytis Cinerea

“…Natural RLs are known to have direct antimicrobial activities against fungi and zoosporic plant pathogens [ 43 ]. In addition, these RLs are able to affect conidial germination and mycelial growth of the necrotrophic fungus B. cinerea [ 32 , 33 , 34 ]. Based on their eliciting activities, four smRLs including Eth-C10, Eth-C12, Car-C12, and Est-C12 were selected for the following experiments.…”

“…These molecules have direct antimicrobial properties against various fungal species in vitro and in vivo [ 25 , 26 , 27 , 28 , 29 , 30 ]. A number of studies have also reported that natural rhamnolipids are able to stimulate plant immunity and trigger induced resistance against various phytopathogens [ 31 , 32 , 33 , 34 ].…”

Biosurfactants in Plant Protection Against Diseases: Rhamnolipids and Lipopeptides Case Study

“…Pseudomonas aeruginosa Botrytis cinerea Spore germination and mycelial growth inhibition Varnier et al, 2009;Monnier et al, 2018 Rha-Rha-C 10 -C 10 , Rha-C 10 -C 10…”

Novel Bioformulations Developed from Pseudomonas putida BSP9 and Its Biosurfactant for Growth Promotion of Brassica juncea (L.)

“…Biosurfactants are biomolecules that are amphiphilic in nature and include a large category of glycolipids, lipopeptides phospholipids, fatty acids and polymeric macromolecules [ 8 , 9 ]. Members of genus Pseudomonas are among the front runners in this context and are reported to produce cyclic lipopeptide and rhamnolipid (a type of glycolipid) biosurfactants [ 10 , 11 ]. Biosurfactants are biodegradable, biocompatible, durable in a range of temperatures and pH and are non-toxic in nature [ 9 , 12 ].…”