Rhamnolipid Biosurfactants as New Players in Animal and Plant Defense against Microbes

Rhamnolipids are known as very efficient biosurfactant molecules. They are used in a wide range of industrial applications including food, cosmetics, pharmaceutical formulations and bioremediation of pollutants. The present review provides an overview of the effect of rhamnolipids in animal and plant defense responses. We describe the current knowledge on the stimulation of plant and animal immunity by these molecules, as well as on their direct antimicrobial properties. Given their ecological acceptance owing to their low toxicity and biodegradability, rhamnolipids have the potential to be useful molecules in medicine and to be part of alternative strategies in order to reduce or replace pesticides in agriculture

<em>In vitro</em> neoformation of grape chimeras (<em>Vitis vinifera</em> L.)

Difference in grape sensitivity to Botrytis cinerea attacks between cultivars was explained by differences in the epidermic tissue of the fruit. Therefore, this work was conducted to create a grape periclinal chimera, whose fruits would combine the skin of a Botrytis tolerant cultivar with a pulp of an another cultivar admitted its good organoleptic quality and productivity. In a first time, graftings of two cultivars (Chardonnay and Pinot noir) were conducted in vitro on 5 different media supplemented with various plant growth regulators. Adventitious shoots were only observed on medium containing BAP and GA3 from a mixed callus structure after four weeks of darkness followed by a light/dark regime. In a second time, RAPD analysis, conducted on these plants, showed their chimerical characteristics

<em>In vitro</em> neoformation of grape chimeras (<em>Vitis vinifera</em> L.)

Difference in grape sensitivity to Botrytis cinerea attacks between cultivars was explained by differences in the epidermic tissue of the fruit. Therefore, this work was conducted to create a grape periclinal chimera, whose fruits would combine the skin of a Botrytis tolerant cultivar with a pulp of an another cultivar admitted its good organoleptic quality and productivity. In a first time, graftings of two cultivars (Chardonnay and Pinot noir) were conducted in vitro on 5 different media supplemented with various plant growth regulators. Adventitious shoots were only observed on medium containing BAP and GA3 from a mixed callus structure after four weeks of darkness followed by a light/dark regime. In a second time, RAPD analysis, conducted on these plants, showed their chimerical characteristics

Response of Grapevine Defenses to UV—C Exposure

International audienceThe defense potential of a tolerant American Vitis rupestris cultivar (Rupestris du Lot) and a susceptible European Vitis vinifera cultivar (Chardonnay) in response to UV-C irradiation was investigated. The expression of eight defense-related genes coding for enzymes of the phenylpropanoid pathway (phenylalanine ammonia lyase and stilbene synthase), the octadecanoid pathway (lipoxygenase), and pathogenesis-related proteins (class I and III chitinases, ß-1,3-glucanase, class 6 pathogenesis-related protein, and class 10 pathogenesis-related protein) was followed by real-time reverse transcription polymerase chain reaction (RT-PCR). Phenolic compound accumulation was monitored by microscopic observation. Accumulation of resveratrol, a major grapevine phytoalexin, was evaluated by HPLC, and chitinase and ß-1,3-glucanase enzyme activities were measured. Both grapevine species responded to UV-C treatment by enhancement of defense mechanisms. Intensity of some defense responses was correlated with tolerance to diseases, as previously described for stilbene accumulation: the tolerant species responded more intensely to UV-C exposure than the susceptible one. UV-C irradiation is a practical and reproducible method for inducing grapevine defense responses and can be useful in determining the defense potential of grapevine cultivars

ß-1,4 cellodextrins, ß-1,3 glucans and a-1,4 oligogalacturonides are potent elicitors of various defense-related responses in grapevine

International audiencePlant cell-wall degradation products can be considered as ‘microbe-induced molecular patterns’ (MIMPs) recognized through plant receptors as ‘pathogen-induced modified self’. So cell-wall oligosaccharides originating from plants can play an important role in the perception of the invading pathogen by the plant. Cellodextrins (CD) are the end-products from cellulose degradation in plant cell walls, consisting og a linear ß-(1,4) linked glucose backbone. The role of these oligosaccharides in triggering plant defense reactions has not yet been established. Here, we investigated the elicitor activity of CD oligomers in grapevine cells. We show that CD triggered induction oxidative burst, transient elevation of [Ca2+]cyt, expression of dense-related genes, and stimulation of chitinase and ß-1,3 glucanase activities in a CD size-dependent manner. Most of these defense reactions were also induced by linear ß-1,3 glucans (ßGlu) and a-1,4 oligogalacturonides (OGA) of different degree of polymerization (DP), but the intensity of some reactions induced by CD was different when compared with ßGlu and OGA effects. Moreover, desensitization assays using H2O2 production showed that cells treated with CD remained fully responsive to a second application of OGA, suggesting a different mode of perception of these oligosaccharides by grape cells. None of CD, ßGlu, or OGA induced HSR gene expression nor did they induce cell death. We suggest that CD could operate via other distinct reaction pathways than Glu and OGA. Our results also highlight the importance of cellulose-derived ß-1,4-glucans as potent MIMPs in plant defense mechanisms

ß-1,4 cellodextrins, ß-1,3 glucans and a-1,4 oligogalacturonides are potent elicitors of various defense-related responses in grapevine

International audiencePlant cell-wall degradation products can be considered as ‘microbe-induced molecular patterns’ (MIMPs) recognized through plant receptors as ‘pathogen-induced modified self’. So cell-wall oligosaccharides originating from plants can play an important role in the perception of the invading pathogen by the plant. Cellodextrins (CD) are the end-products from cellulose degradation in plant cell walls, consisting og a linear ß-(1,4) linked glucose backbone. The role of these oligosaccharides in triggering plant defense reactions has not yet been established. Here, we investigated the elicitor activity of CD oligomers in grapevine cells. We show that CD triggered induction oxidative burst, transient elevation of [Ca2+]cyt, expression of dense-related genes, and stimulation of chitinase and ß-1,3 glucanase activities in a CD size-dependent manner. Most of these defense reactions were also induced by linear ß-1,3 glucans (ßGlu) and a-1,4 oligogalacturonides (OGA) of different degree of polymerization (DP), but the intensity of some reactions induced by CD was different when compared with ßGlu and OGA effects. Moreover, desensitization assays using H2O2 production showed that cells treated with CD remained fully responsive to a second application of OGA, suggesting a different mode of perception of these oligosaccharides by grape cells. None of CD, ßGlu, or OGA induced HSR gene expression nor did they induce cell death. We suggest that CD could operate via other distinct reaction pathways than Glu and OGA. Our results also highlight the importance of cellulose-derived ß-1,4-glucans as potent MIMPs in plant defense mechanisms

Native and sulfated oligoglucuronans as elicitors of defence-related responses inducing protection against Botrytis cinerea of Vitis vinifera

International audienceDuring the past two decades, β-(1,4)-d-polyglucuronic acids (glucuronans) have been intensively described in literature for their physico-chemical and biological properties in different models. In this study, a bacterial glucuronan partially acetylated was degraded by a fungal glucuronan lyase to obtain unsaturated oligogluguronans, finally tested for their potential as elicitors of natural defences in Vitis vinifera. The objective was to correlate biological activities with specific structural features using oligoglucuronans varying in degree of polymerization, acetylation and sulfation. The results demonstrated that different defence reactions elicited by these anionic oligomers were dependent on degree of polymerization and nature of substituents (acetyl or sulfate groups). Acetylated oligoglucuronans with degrees of polymerization of 10 and 14 induced transient production of H2O2 and expression of some defence-related genes (PAL, STS, Chit4c and PGIP). The infection of grapevine leaves by Botrytis cinerea was reduced (23%) after treatment with acetylated oligoglucuronans having degree of polymerization of 14. Sulfated oligoglucuronans were not effective for production of H2O2 but induced strong expression of other defence-related PIN, PGIP genes. This work opens the way to new and valuable strategies to protect V. vinifera and other plants against pathogens