Search

Most drugs or the natural substances reputed to display some biological activity are hydrophobic molecules that demonstrate low bioavailability regardless of their mode of absorption. Resveratrol and its derivatives belong to the chemical group of stilbenes; while stilbenes are known to possess very interesting properties, these are limited by their poor aqueous solubility as well as low bioavailability in animals and humans. Among the substances capable of forming nanomolecular inclusion complexes which can be used for drug delivery, cyclodextrins show spectacular physicochemical and biomedical implications in stilbene chemistry for their possible application in nanomedicine. By virtue of their properties, cyclodextrins have also demonstrated their possible use in green chemistry for the synthesis of stilbene glucosylated derivatives with potential applications in dermatology and cosmetics. Compared to chemical synthesis and genetically modified microorganisms, plant cell or tissue systems provide excellent models for obtaining stilbenes in few g/L quantities, making feasible the production of these compounds at a large scale. However, the biosynthesis of stilbenes is only possible in the presence of the so-called elicitor compounds, the most commonly used of which are cyclodextrins. We also report here on the induction of resveratrol production by cyclodextrins or combinatory elicitation with methyljasmonate in plant cell systems as well as the mechanisms by which they are able to trigger a stilbene response. The present article therefore discusses the role of cyclodextrins in stilbene chemistry both at the physicochemical level as well as the biomedical and biotechnological levels, emphasizing the notion of "easy alliance" between these compounds and stilbenes.

Most drugs or the natural substances reputed to display some biological activity are hydrophobic molecules that demonstrate low bioavailability regardless of their mode of absorption. Resveratrol and its derivatives belong to the chemical group of stilbenes; while stilbenes are known to possess very interesting properties, these are limited by their poor aqueous solubility as well as low bioavailability in animals and humans. Among the substances capable of forming nanomolecular inclusion complexes which can be used for drug delivery, cyclodextrins show spectacular physicochemical and biomedical implications in stilbene chemistry for their possible application in nanomedicine. By virtue of their properties, cyclodextrins have also demonstrated their possible use in green chemistry for the synthesis of stilbene glucosylated derivatives with potential applications in dermatology and cosmetics. Compared to chemical synthesis and genetically modified microorganisms, plant cell or tissue systems provide excellent models for obtaining stilbenes in few g/L quantities, making feasible the production of these compounds at a large scale. However, the biosynthesis of stilbenes is only possible in the presence of the so-called elicitor compounds, the most commonly used of which are cyclodextrins. We also report here on the induction of resveratrol production by cyclodextrins or combinatory elicitation with methyljasmonate in plant cell systems as well as the mechanisms by which they are able to trigger a stilbene response. The present article therefore discusses the role of cyclodextrins in stilbene chemistry both at the physico-chemical level as well as the biomedical and biotechnological levels, emphasizing the notion of "easy alliance" between these compounds and stilbenes. Part of this work is the result of an aid to the postdoctoral training and improvement abroad for Dr Adrián Matencio (number 21229/PD/19) and financed by the Fundación Séneca (Región de Murcia, Spain).

International audience; Neurodegenerative diseases (NDs) are characterized by disorders with progressive deterioration of the structureand/or function of neurons. Genetic mutations can lead to many NDs. Nevertheless, neurodegeneration can alsotake place due to several biological processes. The pathogenesis of several NDs including Alzheimer’s (AD),Parkinson’s (PD), and Huntington’s (HD) diseases are associated with oxidative stress (OS). In order to maintainthe normal functions of neurons, lower levels of reactive oxygen species (ROS) and reactive nitrogen species(RNS) are important, since their increased levels can cause neuronal cell death. It has been found that OSmediated neurodegeneration involves a number of events including mitochondrial dysfunction, Ca2+ overload,and excitotoxicity. A growing number of studies are suggesting the benefit of using polyphenols for the treatmentof neurodegenerative disorders. Indeed, in order to treat most of the NDs, synthetic drugs are extensively usedwhich are found to exert side effects in the course of the treatment. There is mounting evidence that researchershave identified several naturally-occurring chemical compounds in plants, which are used for the management ofNDs. Overall, polyphenolic phytochemicals are safer in nature and have negligible side effects. In this article, wehave focused on the potential efficacy of polyphenols such as epigallocatechin-3-gallate, curcumin, resveratrol,quercetin and methylated polyphenols berberine against the most common neurodegenerative disorders.

Resveratrol and the biosynthetically related stilbenes are plant secondary metabolites with diverse pharmacological effects. The versatile functions of these compounds in plant defense mechanisms as phytoalexins on one hand, and in human health as potential pharmaceutical agents on the other, have attracted lots of interest in recent years to understand their biosynthetic pathways and their biological properties. Because of difficulties in obtaining resveratrol and its glucosylated derivatives as well as oligomeric forms in sufficient amounts for evaluation of their activity by plant sourcing or total synthesis, biotechnology may provide a competitive approach for the large-scale and low cost production of biologically active stilbenes. Additionally, one major limitation in the use of resveratrol and related aglycone derivatives as therapeutic agents is associated with their inherent poor aqueous solubility and low bioavailability. This article examines approaches for the synthesis of potential pharmacologically resveratrol derivatives in vivo by exploiting whole microorganisms, enzymatic and biocatalytic approaches allowing their full utilization for medicine, food and cosmetic applications. These methods also have the advantage of enabling the one-step production of stilbene compounds, compared to the time-consuming and environmentally unfriendly procedures used for their total synthesis or their extraction from plants. Increasing the desired products yield and biological activity through glucosylation (β-D-glucosides versus α-D-glucosides) and oligomerization methodologies of resveratrol including green chemistry methods in organic solvent-free media are discussed as well.

VvWRKY8 interacts with the stilbene synthase transcriptional activator VvMYB14 to repress resveratol biosynthesis in grapevine., Resveratrol (Res) is a stilbenoid, a group of plant phenolic metabolites derived from stilbene that possess activities against pests, pathogens, and abiotic stresses. Only a few species, including grapevine (Vitis), synthesize and accumulate Res. Although stilbene synthases (STSs) have been isolated and characterized in several species, the gene regulatory mechanisms underlying stilbene biosynthesis are still largely unknown. Here, we characterize a grapevine WRKY transcription factor, VvWRKY8, that regulates the Res biosynthetic pathway. Transient and stable overexpression of VvWRKY8 in grapevine results in decreased expression of VvSTS15/21 and VvMYB14, as well as in a reduction of Res accumulation. VvWRKY8 does not bind to or activate the promoters of VvMYB14 and VvSTS15/21; however, it physically interacts with VvMYB14 proteins through their N-terminal domains to prevent them from binding to the VvSTS15/21 promoter. Application of exogenous Res results in the stimulation of VvWRKY8 expression and in a decrease of VvMYB14 and VvSTS15/21 expression in grapevine suspension cells, and in the activation of the VvWRKY8 promoter in tobacco leaves. These results demonstrate that VvWRKY8 represses VvSTS15/21 expression and Res biosynthesis through interaction with VvMYB14. In this context, the VvMYB14-VvSTS15/21-Res-VvWRKY8 regulatory loop may be an important mechanism for the fine-tuning of Res biosynthesis in grapevine.

The rhizospheric Bacillus subtilis PTA-271 (271) and endophytic Pseudomonas fluorescens PTA-CT2 (CT2) and Pantoea agglomerans PTA-AF2 (AF2) bacteria are able to induce systemic resistance (ISR) in grapevine against B. cinerea, but ISR markers and their costs remained unknown in vineyards. In this study, we investigated the relationship between the effectiveness of single and binary combinations of selected bacteria to induce ISR and their ability to trigger phytoalexin accumulation, as a potential marker for disease resistance, in leaves and berries, as well as their impact on grape yield in vineyards. Grapevine plants were treated during 2006 in two vineyards by drenching soil with single or binary mixtures of bacteria. Induced resistance against B. cinerea was evaluated and stilbenic phytoalexins were analyzed by HPLC in both leaves and berries. Grape yield was also assessed as number and weight of clusters at ripening. Both single and mixtures of bacteria were effective in reducing gray mold severity in the leaves and berries in vineyards. Disease control was accompanied by a significant accumulation of stilbenic phytoalexins, trans-resveratrol and e-viniferin, in both leaves and berries in the bacterized plants. δ-Viniferin also accumulated, but only in berries of the treated plants. Reduction of disease symptoms and accumulation of resveratrol and viniferins were higher in the plants treated with single CT2 compared to AF2 and 271. Treatment of grapevine plants with binary mixtures of these isolates resulted in a significant performance of CT2+AF2 in leaves and CT2+271 in berries. On the other hand, bacterial treatments did not show any negative effect on grape yield. These results revealed the efficacy of CT2 alone or in combination with AF2 or with 271 in triggering grapevine resistance against B. cinerea and enhancing systemic accumulation of resveratrol and viniferins, without compromising grape yield.

IF 2.861; International audience; A new resveratrol dimer (1) called labruscol, has been purified by centrifugal partition chromatography of a crude ethyl acetate stilbene extract obtained from elicited grapevine cell suspensions of Vitis labrusca L. cultured in a 14-liter stirred bioreactor. One dimensional (1D) and two dimensional (2D) nuclear magnetic resonance (NMR) analyses including ¹H, 13C, heteronuclear single-quantum correlation (HSQC), heteronuclear multiple bond correlation (HMBC), and correlation spectroscopy (COSY) as well as high-resolution electrospray ionisation mass spectrometry (HR-ESI-MS) were used to characterize this compound and to unambiguously identify it as a new stilbene dimer, though its relative stereochemistry remained unsolved. Labruscol was recovered as a pure compound (>93%) in sufficient amounts (41 mg) to allow assessment of its biological activity (cell viability, cell invasion and apoptotic activity) on two different cell lines, including one human skin melanoma cancer cell line HT-144 and a healthy human dermal fibroblast (HDF) line. This compound induced almost 100% of cell viability inhibition in the cancer line at a dose of 100 μM within 72 h of treatment. However, at all tested concentrations and treatment times, resveratrol displayed an inhibition of the cancer line viability higher than that of labruscol in the presence of fetal bovine serum. Both compounds also showed differential activities on healthy and cancer cell lines. Finally, labruscol at a concentration of 1.2 μM was shown to reduce cell invasion by 40%, although no similar activity was observed with resveratrol. The cytotoxic activity of this newly-identified dimer is discussed.

Resveratrol and its derivatives are a class of polyphenolic compounds recognized for their outstanding biological properties based on clinical trials. In addition, their possible uses in nutraceutics, cosmetics, and as pharmaceutics create a need for large-scale production with the possibility to use sustainable sources. In this review, we report on the biotechnological production of resveratrol and some of its derivatives through plant cell suspensions, such as grapevine cell culture systems. These cultures usually need elicitation. Methyljasmonate, cyclodextrins, the combination of both and chitosan are the elicitors leading to the best responses in terms of resveratrol amounts produced in flasks. Production performances of resveratrol can be optimized in flasks for scale-up in large culture volumes. We summarize the plant cell culture systems used for resveratrol bioproduction and transfer experiments from flasks to bioreactors as well as elicitor-mediated upregulation of the defense genes in those plant culture systems.

Stilbenes are defense molecules produced by grapevine in response to stresses including various elicitors and signal molecules. Together with their prominent role in planta, stilbenes have been the center of much attention in recent decades due to their pharmaceutical properties. With the aim of setting up a cost-effective and high purity production of resveratrol derivatives, hairy root lines were established from Vitis vinifera cv Pinot Noir 40024 to study the organ-specific production of various stilbenes. Biomass increase and stilbene production by roots were monitored during flask experiments. Although there was a constitutive production of stilbenes in roots, an induction of stilbene synthesis by methyl jasmonate (MeJA) after 18 days of growth led to further accumulation of ε-viniferin, δ-viniferin, resveratrol and piceid. The use of 100 µM MeJA after 18 days of culture in the presence of methyl-β-cyclodextrins (MCDs) improved production levels, which reached 1034 µg/g fresh weight (FW) in roots and 165 mg/L in the extracellular medium, corresponding to five-and 570-fold increase in comparison to control. Whereas a low level of stilbene excretion was measured in controls, addition of MeJA induced excretion of up to 37% of total stilbenes. The use of MCDs increased the excretion phenomenon even more, reaching up to 98%. Our results demonstrate the ability of grapevine hairy roots to produce various stilbenes. This production was significantly improved in response to elicitation by methyl jasmonate and/or MCDs. This supports the interest of using hairy roots as a potentially valuable system for producing resveratrol derivatives.

International audience; Resveratrol and related oligostilbenes are defense molecules produced by grapevine in response to stresses including various elicitors or signal molecules. Together with their prominent role in planta, these compounds have been the center of much attention in recent decades due to their pharmacological properties. The cost-effective production of resveratrol derivatives such as viniferins or more structurally complex stilbene oligomers remains a challenging task. In this study, the chemical diversity of stilbenes produced by Vitis vinifera Pinot Noir hairy roots was investigated after elicitation for 4 days with a mixture of methyl jasmonate (100 μM) and cyclodextrins (50 mM). Two crude extracts obtained from the culture medium and from the hairy roots were fractionated by centrifugal partition chromatography. The fractions were chemically investigated by two complementary identification approaches involving a 13C NMR-based dereplication method and liquid chromatography coupled to mass spectrometry (LC-MS). In total, groups of 21 and 18 molecules, including flavonoids and stilbenes, were detected in the culture medium and root extracts, respectively. These included resveratrol monomers, dimers, trimers, and a tetramer, thus highlighting the ability of elicited hairy root culture systems to synthesize a wide diversity of secondary metabolites of pharmaceutical significance. The main compounds were unambiguously identified as trans-resveratrol, ε-viniferin, trans-piceatannol, pallidol, scirpusin A, eriodictyol, naringenin, vitisin B, and maackin.

Plant cell cultures constitute pesticide-free sources for obtaining plant secondary metabolites or plant extracts. Additionally, they do not contain any fungal contaminants, mycotoxins or heavy metals providing to the consumer potential health benefits and justifying the development of this technology at an industrial scale. Significant production levels of these secondary metabolites can be obtained through the use of elicitors, which activate plant defense mechanisms. Resveratrol, a well-known grapevine polyphenolic compound which possesses potent antioxidant and antiaging activities as well as a protective action on skin, is a good example of such plant secondary metabolites. Resveratrol and its oligomeric derivatives are used by several companies of cosmetic products but their extraction from vine stems and similar vegetal sources remains difficult. Therefore grapevine cell suspensions could represent interesting systems for the large-scale bioproduction of those compounds. Here we present an update of the methods used for the production of phytostilbenes by using grapevine cell cultures and the results obtained.

Resveratrol, a stilbenic compound deriving from the phenyalanine/polymalonate route, being stilbene synthase the last and key enzyme of this pathway, recently has become the focus of a number of studies in medicine and plant physiology. Increased demand for this molecule for nutraceutical, cosmetic and possibly pharmaceutic uses, makes its production a necessity. In this context, the use of biotechnology through recombinant microorganisms and plants is particularly promising. Interesting results can indeed arise from the potential of genetically modified microorganisms as an alternative mechanism for producing resveratrol. Strategies used to tailoring yeast as they do not possess the genes that encode for the resveratrol pathway, will be described. On the other hand, most interest has centered in recent years, onSTSgene transfer experiments from various origins to the genome of numerous plants. This work also presents a comprehensive review on plant molecular engineering with theSTSgene, resulting in disease resistance against microorganisms and the enhancement of the antioxidant activities of several fruits in transgenic lines.

A cell suspension culture was developed from calli of grape rootstock 41B in order to study the bioproduction of resveratrol. While 41B grape cultures produced no resveratrol, methyljasmonate (MeJA) elicitor treatment activated its production in a dose dependent manner. The concentration of 0.2 mM MeJA was optimal for efficient production and high accumulation of resveratrol (150 mg/L) in flask experiments. Microscopic analysis of cells monitored for viability showed that MeJA elicitor triggered expression of resveratrol fluorescence within the cells. These results led to scale-up of the culture in a 2 L stirred bioreactor where a resveratrol production of 209 mg/L being secreted into the liquid medium, corresponding to 90% of the total production. Liquid/liquid extraction of the culture medium and a solid/liquid extraction of the cells showed that other stilbenes were also produced. For the first time, trans-ɛ-viniferin, trans-δ-viniferin, and a trans-3-methylviniferin as well as trans-piceatannol were identified in a 2 L bioreactor cell cultures of grapevine. Furthermore, a one step FPLC method was developed for the purification of resveratrol and ɛ-viniferin.

In grapevine, stimulation of defence responses was evidenced in response to various types of abiotic stresses in both leaves and berries, as revealed by the increasing expression of genes encoding defence-related proteins or the stimulation of their corresponding activities. However, the capability of inflorescences to respond to abiotic stresses has never been investigated. Therefore, plant defence reactions in response to UV-C irradiation were followed in inflorescences and young clusters focusing on both bunchstems (peduncle and pedicels) and developing flowers/berries from separated floral buds stage [Biologische Bundesanstalt, Bundessortenamt and CHemical industry (BBCH) stage 57] to groat-sized berries stage (BBCH 73). For this purpose, the expression of various genes coding for pathogenesis-related (PR) proteins (class I and III chitinases, Chi1b and CH3; beta-1,3-glucanase, GLUC), an enzyme of the phenylpropanoid pathway (phenylalanine ammonia-lyase, PAL), and stilbene synthase (STS) was analysed in parallel with variations of chitinase activity and the accumulation of the phytoalexin resveratrol. Multiple defence responses were induced in bunchstems of both inflorescences and clusters following UV-C treatment. First, expression of genes encoding PR proteins was stimulated and chitinase activity was enhanced. Secondly, PAL and STS expression increased in association with resveratrol accumulation. Amazingly, none of the tested defence processes was induced in grapevine flowers following UV-C exposure, whatever the stage analysed. Similarly, in berries at fruit set, induction of gene expression was weak and neither an increase in chitinase activity nor resveratrol synthesis was noticed. However, in groat-sized berries, responsiveness to UV-C increased, as revealed by the induction of CH3, PAL, and STS expression, together with resveratrol accumulation. The differential responsiveness between bunchstems, flowers, and berries is discussed.

The production of stilbene phytoalexins was analyzed in Vitis sp. protoplasts during isolation and culture, by HPLC. The results showed that trans -resveratrol could be detected as early as the fourth hour of digestion and accumulated during the digestion process, while the healthy donor material was devoid. Resveratrol production was due to de novo activation of the Vst1 gene encoding for the stilbene synthase (EC 2.3.1.95) responsible for resveratrol formation. When in culture, leaf protoplasts, whatever the genotype, continued to produce large amounts of resveratrol within the first week of culture, whereas, during the second week, a decrease in resveratrol content was observed, in parallel to a decrease in protoplast viability. Other phytoalexins derived from the resveratrol were produced during the culture, mainly an inducible resveratrol dehydrodimer analogous to e-viniferin and, to a lesser extent, pterostilbene. In order to determine the inducer of phytoalexin production, effects of culture conditions were evaluated on resveratrol production and discussed.

The phytoalexin production potential of three American Vitis species and that of three cultivars of Vitis vinifera were evaluated in response to UV-C irradiation. Time course changes in resveratrol, piceid, epsilon-viniferin, and pterostilbene contents were studied within 3 days after a short UV-C irradiation. Results show that the two major stilbenes accumulated as a response to UV-C elicitation are resveratrol and epsilon-viniferin, a resveratrol dehydrodimer, the concentration of both compounds usually reaching quantities >100 microgram/g of fresh weight. In contrast, piceid and pterostilbene were constantly produced in low quantities. Owing to the results obtained, the role of stilbene phytoalexins in the resistance of grapevines to diseases is discussed.

Observations using light microscopy showed that approximately 30% of Botrytis cinerea conidia treated with semi-lethal concentrations (i.e., 60 μg/ml) of the grapevine phytoalexin resveratrol possessed intracellular brown coloration. This coloration was never observed in the absence of resveratrol or in conidia treated with resveratrol together with sulfur dioxide (antioxidant compound) or sodium diethyldithiocarbamate (inhibitor of laccase action), suggesting that discoloration resulted from the laccase-mediated oxidation of resveratrol. Further studies using transmission electron microscopy enabled the observation of particular intravacuolar spherical vesicles and of granular material deposits along the tonoplast. These observations are likely to be related to the oxidation of resveratrol by an intracellular laccase-like stilbene oxidase of B. cinerea.

Resveratrol, a grapevine phytoalexin, is metabolized by a laccase-like stilbene-oxidase of Botrytis cinerea, the causal organism for grey mould. Characterization of one major metabolite formed during this degradation process as a resveratrol dehydrodimer allowed us to precize the reaction mechanism of this enzyme on stilbenes.

The ability of eight isolates of Botrytis cinerea to degrade the stilbene phytoalexins, resveratrol and pterostilbene, was compared with their pathogenicity to grapevines. All strains which degraded resveratrol and pterostilbene were highly or moderately pathogenic to in vitro cultures of grapevines (Vitis rupestris) after inoculation with agar disks containing mycelium, while those which were unable to degrade phytoalexins were non-pathogenic. In all cases, the hydroxystilbene-degrading activity was related to the presence of laccase activity in the culture filtrates, as shown by using syringaldazine as substrate. The role of laccase-mediated degradation of phytoalexins in relation to pathogenicity of B. cinerea to grapevines in discussed.

Le resveratrol (3,5,4'-trihydroxystilbene) est un des mebolites de stress produit par la vigne en reponse a une infection parasitaire ou une blessure. La distribution de cette molecule dans des lesions limitees causees par Botrytis cinerea sur des grappes de raisins a maturite au vignoble a ete etudiee. Le resveratrol est localise principalement dans les fruits sains entourant les zones infectees. Cette reponse localisee contribue a limiter l'extension du pathogene tant que les conditions climatiques lui sont defavorables. Lorsque les conditions deviennent favorables; c'est-a-dire apres une periode humide et chaude, une expansion rapide des lesions est alors observee sur les fruits en depit d'une synthese croissante de resveratrol dans les grappes, synthese qui peut atteindre trois a cinq fois les valeurs trouvees avant l'intensification de la maladie. Des teneurs importantes en resveratol ont egalement ete trouvees dans les fruits collectes a partir de grappes ne manifestant apparemment aucun signe d'expression de la maladie, ce qui suggere que la reponse phytoalexine de la plante est initiee tres rapidement apres la reconnaissance du pathogene par l'hote. L'implication de signaux endogenes provenant de la plante ou du champignon dans l'induction des systemes de defense de l'hote a ete discutee

Resveratrol (trans-3,5,4'-trihydroxystilbene) is a phytoalexin produced by grapevines in response to fungal infection, particularly to Botrytis cinerea, the causal organism for gray mold. This compound is known to occur in grapes as well as in wine and claimed to protect against heart diseases. Two factors that can modify resveratrol levels in wine were studied here: (1) the influence of classical white or red winemaking practices and (2) the effect of grape Botrytis levels on the resveratrol content of wines. Analysis of resveratrol was carried out by HPLC and GC-MS. Maceration on the grape skins increased the extraction of resveratrol by ca. 10-fold compared to nonmacerated wines. Paradoxically, lower concentrations of resveratrol were observed in wines made from highly Botrytis infected grapes than in those vinted from healthy and moderately infected grapes. Finally, this study has clearly established the presence of high quantities of the cis isomer of resveratrol in wine, a form only slightly detectable in grapes

International audience; Many roles have been ascribed to stilbenes, namely as antimicrobial, deterrent or repellent compounds in plants, protecting them from attacks by fungi, bacteria, nematodes or herbivores, acting both as constitutive and active defense (phytoalexin) compounds. More recently, stilbenes (especially resveratrol and its derivatives) were acclaimed for their wondrous effects and wide range of purported healing and preventive powers as cardioprotective, antitumor, neuroprotective and antioxidant agents. Although there is a huge number of works concerning the role of resveratrol in human health, reports on the antifungal activity of this compound are still scarce. This study was thus conducted in order to investigate the toxicity of resveratrol at an ultrastructural level to dormant conidia of Botrytis cinerea, the causal microorganism for gray mold. In grapevine particularly, this disease can affect all the green organs but is particularly damaging for ripening berries. Observations using transmission electron microscopy showed the occurrence of damages on conidia treated with sub-lethal doses, that is, 60 mu g/mL (2.6 x 10(-4) M) of resveratrol, a concentration usually reached in grapevine leaves and grape berries challenged by this pathogen. These results provide further data about the overall mode of action of this phytoalexin and its role in the B. cinerea/grapevine interaction. (C) 2012 Elsevier B.V. All rights reserved.

Verhagen, B., Trotel-Aziz, P., Jeandet, P., Baillieul, F., and Aziz, A. 2011. Improved resistance against Botrytis cinerea by grapevine-associated bacteria that induce a prime oxidative burst and phytoalexin production. Phytopathology 101:768-777. Bacteria such as Pantoea agglomerans (Pa-AF2), Bacillus subtilis (Bs271), Acinetobacter lwoffii (Al-113), and Pseudomonas fluorescens (PfCT2), originating from the vineyard, can induce defense responses and enhance resistance of grapevine against the fungal pathogen Botrytis cinerea. The perception of these bacteria by plant cells or tissues in relation to their activities remains unknown. In this study, we examined the relationships between the activity of each bacterium to induce or prime some defense responses, and its effectiveness to induce resistance in grapevine against B. cinerea. We showed that all selected bacteria are capable of inducing early oxidative burst and phytoalexin (transresveratrol and trans-e-viniferin) production in grapevine cells and leaves. Pf-CT2 and Al-113 induced higher H2O2 and trans-resveratrol accumulations, and were able to further prime plants for accelerated phytoalexin production after B. cinerea challenge. These two bacteria were also the most effective in inducing local and systemic resistance. A similar level of induced resistance was observed with live Pa-AF2 which also induced but not primed a greater accumulation of trans-resveratrol. However, Bs-271, which was less effective in inducing resistance, induced a lower trans-resveratrol synthesis, without priming activity. Treatment of grapevine cells with growing medium or crude extract of the bacteria quickly and strongly enhanced oxidative burst compared with the live bacteria. However, both treatments resulted in comparable amounts of phytoalexins and induced local and systemic resistance to B. cinerea as compared with those induced by living bacteria, with extracts from PfCT2 and Al-113 being the most effective. Together, these results indicate that induced resistance can be improved by treatment with bacteria or derived compounds which induced or primed plants for enhanced phytoalexin accumulation.

Recent studies have shown that resveratrol (3,5,4'‐trihydroxystilbene), a phytoalexin related to grape disease resistance, could occur in American and Bordeaux wines. It was also suggested that resveratrol might have cardioprotective activities in humans, as a result of drinking wine. We report here the presence of this compound in Burgundy wines. Analysis of resveratrol in wine was carried out using gas chromatography and gas chromatography—mass spectrometry.

Stilbenic compounds recently have become the focus of a number of studies in medicine and plant physiology as well as have emerged as promising molecules that potentially affect human health. Stilbenes are relatively simple compounds synthesized by plants and deriving from the phenyalanine/polymalonate route, the last and key enzyme of this pathway being stilbene synthase. Here, we review the biological significance of stilbenes in plants together with their biosynthesis pathway and their metabolism both by fungi and in planta. Special attention will be paid to the role of stilbenic molecules as phytoalexins.

The ability of grapevine in vitro cultures to synthesise the phytoalexin precursor resveratrol in response to ultraviolet light irradiations is investigated in order to develop methods for screening for resistance to grey mould (Botrytis cinerea Pers.) in grapevines produced as a result of somatic embryogenesis. It is demonstrated that resveratrol formation can be reproducibly induced in leaves of in vitro plantlets. Differences in the production of resveratrol among the three varieties of Vitis vinifera tested (Pinot Noir, Chardonnay and Cabernet Sauvignon) were consistent with observations regarding their field susceptibility to grey mould. The use of phytoalexin induction and of in vitro methods as a tool for selection of Vitis resistant genotypes in early screening tests is discussed.

A method using HPLC analysis has been used to compare the level of resveratrol and its derivatives, piceid, pterostilbene and epsilon-viniferin, in grapevine berries of three Vitis vinifera varieties. The concentration of these compounds has been evaluated in healthy and Botrytis cinerea infected grape clusters, both in natural vineyard conditions and in response to UV elicitation.

Trans-resveratrol is a phenolic plant compound that has been recognized for its benefits on human health. Currently, increasing demand for trans-resveratrol for nutraceutical, cosmetic, and putatively pharmaceutic uses makes its production from sustainable sourcing a necessity. In this context, the use of biotechnology through recombinant microorganisms and plant cell suspensions is particularly promising because it represents a reliable alternative method of trans-resveratrol production under controlled conditions. Tailoring yeast or bacteria with genes that encode enzymes of the trans-resveratrol pathway and further elicitation of plant-cell metabolism might represent powerful strategies for increased trans-resveratrol bioproduction. This review aims at describing and comparing these different available methods, with a focus on their respective advantages, limits and perspectives as a basis for scale-up in large culture volumes.

The grapevine phytoalexin resveratrol, the synthesis of which is achieved by stilbene synthase (STS), displays a wide range of biological effects. Most interest has centred, in recent years, on STS gene transfer experiments from grapevine to the genome of numerous plants. This work presents a comprehensive review on plant molecular engineering with the STS gene. Gene and promoter options are discussed, namely the different promoters used to drive the transgene, as well as the enhancer elements and/or heterologous promoters used to improve transcriptional activity in the transformed lines. Factors modifying transgene expression and epigenetic modifications, for instance transgene copy number, are also presented. Resveratrol synthesis in plants, together with that of its glucoside as a result of STS expression, is described, as is the incidence of these compounds on plant metabolism and development. The ectopic production of resveratrol can lead to broad-spectrum resistance against fungi in transgenic lines, and to the enhancement of the antioxidant activities of several fruits, highlighting the potential role of this compound in health promotion and plant disease control.

Resistance of plants to infection by phytopathogenic microorganisms is the result of multiple defense reactions comprising both constitutive and inducible barriers. In grapevine, the most frequently observed and best characterized defense mechanisms are the accumulation of phytoalexins and the synthesis of PR-proteins. Particular attention has been given here to stilbene phytoalexins produced by Vitaceae, specifically, their pathway of biosynthesis (including stilbene phytoalexin gene transfer experiments to other plants) and their biological activity together with fungal metabolism.

Phytoalexins, antimicrobial compounds, synthesized by a plant in response to infection or a variety of stresses are known to be the most efficient way by which grapevines withstand an attack by Botrytis cinerea Pers., the causal organism for grey mould. In that plant, such responses include the production of a simple stilbene, resveratrol, and the biosynthetically related compounds, viniferins and pterostilbene. If stilbene-type phytoalexins represent a contributory factor in the resistance of grapevines to B.cinerea, the capacity of the pathogen to metabolize antifungal compounds released by the host could also play a significant role in the outcome of the interaction between grapevines and B.cinerea.Indeed, the net accumulation of phytoalexins within plant tissues infected by various pathogens is probably controlled by a balance which may result, on the one hand, from the ability of the host cells to resist colonization by creating an inhibitory barrier for the parasite, and, on the other hand, from tolerance of the pathogen to antifungal compounds produced by the plant and from its ability to detoxify the phytoalexins to which it is exposed. Thus, the resistance of plants to infection depends on the phytoalexin production/degradation balance following attack by the pathogen. A variety of factors can alter this balance in favour of either the parasite or the host, resulting in non-compatible or compatible interactions. Among these, the capacity of B.cinerea to detoxify the phytoalexins produced by grapevines was investigated. We present here good evidence that this fungus produces a stilbene oxidase which can degrade resveratrol and pterostilbene. No detoxication of stilbenes is detected during the germination process in vitro, suggesting that stilbene-degrading activity does not seem to be constitutive in dormant conidia of Botrytis.