Field-Based Metabolomics of Vitis vinifera L. Stems Provides New Insights for Genotype Discrimination and Polyphenol Metabolism Structuring

Grape accumulates numerous polyphenols with abundant health benefit and organoleptic properties that in planta act as key components of the plant defense system against diseases. Considerable advances have been made in the chemical characterization of wine metabolites particularly volatile and polyphenolic compounds. However, the metabotyping (metabolite-phenotype characterization) of grape varieties, from polyphenolic-rich vineyard by-product is unprecedented. As this composition might result from the complex interaction between genotype, environment and viticultural practices, a field experiment was setting up with uniform pedo-climatic factors and viticultural practices of growing vines to favor the genetic determinism of polyphenol expression. As a result, UPLC-MS-based targeted metabolomic analyses of grape stems from 8 Vitis vinifera L. cultivars allowed the determination of 42 polyphenols related to phenolic acids, flavonoids, procyanidins, and stilbenoids as resveratrol oligomers (degree of oligomerization 1–4). Using a partial least-square discriminant analysis approach, grape stem chemical profiles were discriminated according to their genotypic origin showing that polyphenol profile express a varietal signature. Furthermore, hierarchical clustering highlights various degree of polyphenol similarity between grape varieties that were in agreement with the genetic distance using clustering analyses of 22 microsatellite DNA markers. Metabolite correlation network suggested that several polyphenol subclasses were differently controlled. The present polyphenol metabotyping approach coupled to multivariate statistical analyses might assist grape selection programs to improve metabolites with both health-benefit potential and plant defense traits

Mechanical stress rapidly induces E-resveratrol and E-piceatannol biosynthesis in grape canes stored as a freshly-pruned byproduct

International audienceGrape canes represent a promising source of bioactive phytochemicals. However the stabilization of the raw material after pruning remains challenging. We recently reported the induction of stilbenoid metabolism after winter pruning including a strong accumulation of E-resveratrol and E-piceatannol during the first six weeks of storage. In the present study, the effect of mechanical wounding on freshly-pruned canes was tested to increase the induction of stilbenoid metabolism. Cutting the grape canes in short segments immediately after pruning triggered a transient expression of phenylalanine ammonia-lyase (PAL) and stilbene synthase (STS) genes, followed by a rapid accumulation of E-resveratrol and E-piceatannol. The degree of stilbenoid induction was related to the intensity of mechanical wounding. Data suggest that a global defense response is triggered involving jasmonate signaling, PR proteins and stilbenoid metabolism. Mechanic

Composition and Tissue-Specific Distribution of Stilbenoids in Grape Canes Are Affected by Downy Mildew Pressure in the Vineyard

Grape canes are byproducts of viticulture containing valuable bioactive stilbenoids including monomers and oligomers of E-resveratrol. Although effective contents in stilbenoids are known to be highly variable, the determining factors influencing this composition remain poorly understood. As stilbenoids are locally induced defense compounds in response to phytopathogens, this study assessed the impact of downy mildew infection during the growing season on the stilbenoid composition of winter-harvested grape canes. The spatial distribution between pith, conducting tissues, and cortex of E-piceatannol, E-resveratrol, E-ε-viniferin, ampelopsin A, E-miyabenol C, Z/E-vitisin B, hopeaphenol, and isohopeaphenol in grape canes from infected vineyards was strongly altered. In conducting tissues, representing the main site of stilbenoid accumulation, E-ε-viniferin content was higher and E-resveratrol content was lower. These findings suppose that the health status in vineyards could modify the composition of stilbenoids in winter-harvested grape canes and subsequently the potential biological properties of the valuable extracts

Biosynthetic Origin of <i>E</i>-Resveratrol Accumulation in Grape Canes during Postharvest Storage

Grape canes are vineyard waste products containing valuable phytochemicals of medicine and agriculture interest. Grape canes storage is critical for the accumulation of these bioactive compounds. In the present study, we investigated the changes in stilbenoid phytochemical composition during grape cane storage and the influence of the temperature on final concentrations. A strong increase in the concentration of the monomer E-resveratrol (approximately 40-fold) was observed during the first 6 weeks of storage at 20 °C in eight different grape varieties without any change in oligomer concentrations. The E-resveratrol accumulation was temperature-dependent with an optimal range at 15-20 °C. A 2 h heat-shock treatment aiming at protein denaturation inhibited E-resveratrol accumulation. The constitutive expression of key genes involved in the stilbene precursor biosynthesis along with an induction of stilbene synthase (STS) expression during the first weeks of storage contribute to a de novo biosynthesis of E-resveratrol in pruned wood grapes

Table_1_Field-Based Metabolomics of Vitis vinifera L. Stems Provides New Insights for Genotype Discrimination and Polyphenol Metabolism Structuring.docx

<p>Grape accumulates numerous polyphenols with abundant health benefit and organoleptic properties that in planta act as key components of the plant defense system against diseases. Considerable advances have been made in the chemical characterization of wine metabolites particularly volatile and polyphenolic compounds. However, the metabotyping (metabolite-phenotype characterization) of grape varieties, from polyphenolic-rich vineyard by-product is unprecedented. As this composition might result from the complex interaction between genotype, environment and viticultural practices, a field experiment was setting up with uniform pedo-climatic factors and viticultural practices of growing vines to favor the genetic determinism of polyphenol expression. As a result, UPLC-MS-based targeted metabolomic analyses of grape stems from 8 Vitis vinifera L. cultivars allowed the determination of 42 polyphenols related to phenolic acids, flavonoids, procyanidins, and stilbenoids as resveratrol oligomers (degree of oligomerization 1–4). Using a partial least-square discriminant analysis approach, grape stem chemical profiles were discriminated according to their genotypic origin showing that polyphenol profile express a varietal signature. Furthermore, hierarchical clustering highlights various degree of polyphenol similarity between grape varieties that were in agreement with the genetic distance using clustering analyses of 22 microsatellite DNA markers. Metabolite correlation network suggested that several polyphenol subclasses were differently controlled. The present polyphenol metabotyping approach coupled to multivariate statistical analyses might assist grape selection programs to improve metabolites with both health-benefit potential and plant defense traits.</p