Abstract
Natural rhamnolipids are potential biocontrol agents for plant protection against bacterial and fungal diseases. In this work, we synthetized new synthetic mono-rhamnolipids (smRLs) consisting in a rhamnose connected to a simple acyl chain and differing by the nature of the link and the length of the lipid tail. We then investigated the effects of these ether, ester, carbamate or succinate smRL derivatives on Botrytis cinerea development, symptoms spreading on tomato leaves and immune responses in tomato plants. Our results demonstrate that synthetic smRLs are able to trigger early and late immunity-related plant defense responses in tomato and increase plant resistance against B. cinerea in controlled conditions. Structure-function analysis showed that chain length of the lipidic part and type of acyl chain were critical to smRLs immune activity and to the extent of symptoms caused by the fungus on tomato leaves.
Highlights
The surveillance system of plant immunity relies on the perception by plant IP receptors (IPRs) of invasion patterns (IPs), known as elicitors, to trigger plant defense responses [1,2,3,4]
Our results suggest that synthetic mono-rhamnolipids (smRLs) with acyl chain length ranging from 10 to 12 carbons are perceived by tomato, inducing the plant defence mechanisms. smRLs have a direct antifungal effect by both altering Botrytis conidial spore germination and mycelial development
Naturals Rhamnolipids (RLs) are amphiphilic molecules typically composed of a hydrophobic alkyl chain linked through a glycosidic bond to mono- or di-rhamnoses
Summary
The surveillance system of plant immunity relies on the perception by plant IP receptors (IPRs) of invasion patterns (IPs), known as elicitors, to trigger plant defense responses [1,2,3,4]. Molecules 2020, 25, 3108 elicitors are small compounds, structurally distinct from natural IPs or chemically inspired by IPs [3,11] They can trigger the plant immune response by mimicking IP perception or IP-triggered plant signaling. Rhamnolipid surfactants are well known for their biocompatibility, biodegradability or low toxicity to non-target organisms [22,23,24] 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 reported that natural rhamnolipids are able to stimulate plant immunity and trigger induced resistance against various phytopathogens [31,32,33,34]. Our results suggest that smRLs with acyl chain length ranging from 10 to 12 carbons are perceived by tomato, inducing the plant defence mechanisms. smRLs have a direct antifungal effect by both altering Botrytis conidial spore germination and mycelial development
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