title: Transcriptome and metabolite profiling reveals that prolonged drought modulates the phenylpropanoid and terpenoid pathway in white grapes (Vitis vinifera L.).
abstract: BACKGROUND
  Secondary metabolism contributes to the adaptation of a plant to its environment. In wine grapes, fruit secondary metabolism largely determines wine quality. Climate change is predicted to exacerbate drought events in several viticultural areas, potentially affecting the wine quality. In red grapes, water deficit modulates flavonoid accumulation, leading to major quantitative and compositional changes in the profile of the anthocyanin pigments; in white grapes, the effect of water deficit on secondary metabolism is still largely unknown.
  
  
  RESULTS
  In this study we investigated the impact of water deficit on the secondary metabolism of white grapes using a large scale metabolite and transcript profiling approach in a season characterized by prolonged drought. Irrigated grapevines were compared to non-irrigated grapevines that suffered from water deficit from early stages of berry development to harvest. A large effect of water deficit on fruit secondary metabolism was observed. Increased concentrations of phenylpropanoids, monoterpenes, and tocopherols were detected, while carotenoid and flavonoid accumulations were differentially modulated by water deficit according to the berry developmental stage. The RNA-sequencing analysis carried out on berries collected at three developmental stages-before, at the onset, and at late ripening-indicated that water deficit affected the expression of 4,889 genes. The Gene Ontology category secondary metabolic process was overrepresented within up-regulated genes at all the stages of fruit development considered, and within down-regulated genes before ripening. Eighteen phenylpropanoid, 16 flavonoid, 9 carotenoid, and 16 terpenoid structural genes were modulated by water deficit, indicating the transcriptional regulation of these metabolic pathways in fruit exposed to water deficit. An integrated network and promoter analyses identified a transcriptional regulatory module that encompasses terpenoid genes, transcription factors, and enriched drought-responsive elements in the promoter regions of those genes as part of the grapes response to drought.
  
  
  CONCLUSIONS
  Our study reveals that grapevine berries respond to drought by modulating several secondary metabolic pathways, and particularly, by stimulating the production of phenylpropanoids, the carotenoid zeaxanthin, and of volatile organic compounds such as monoterpenes, with potential effects on grape and wine antioxidant potential, composition, and sensory features.
authors.affiliation: Department of Food Quality and Nutrition, Research and Innovation Centre, Fondazione Edmund Mach, Via E. Mach 1, 38010, San Michele all'Adige, Italy.|Dipartimento di Scienze Agro-alimentari, Ambientali e Animali, University of Udine, Via delle Scienze 208, 33100, Udine, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Savoi
authors.affiliation: Wine Research Centre, The University of British Columbia, 2205 East Mall, Vancouver, BC, V6T 1Z4, Canada.
authors.forename: Darren C J
authors.initials: DC
authors.lastname: Wong
authors.affiliation: Department of Food Quality and Nutrition, Research and Innovation Centre, Fondazione Edmund Mach, Via E. Mach 1, 38010, San Michele all'Adige, Italy.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Arapitsas
authors.affiliation: Dipartimento di Scienze Agro-alimentari, Ambientali e Animali, University of Udine, Via delle Scienze 208, 33100, Udine, Italy.|Istituto di Genomica Applicata, Parco Scientifco e Tecnologico Luigi Danieli, via Jacopo Linussio 51, 33100, Udine, Italy.
authors.forename: Mara
authors.initials: M
authors.lastname: Miculan
authors.affiliation: Dipartimento di Scienze Agro-alimentari, Ambientali e Animali, University of Udine, Via delle Scienze 208, 33100, Udine, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Bucchetti
authors.affiliation: Dipartimento di Scienze Agro-alimentari, Ambientali e Animali, University of Udine, Via delle Scienze 208, 33100, Udine, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Peterlunger
authors.affiliation: The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Midreshet Ben-Gurion, Israel.
authors.forename: Aaron
authors.initials: A
authors.lastname: Fait
authors.affiliation: Department of Food Quality and Nutrition, Research and Innovation Centre, Fondazione Edmund Mach, Via E. Mach 1, 38010, San Michele all'Adige, Italy.
authors.forename: Fulvio
authors.initials: F
authors.lastname: Mattivi
authors.affiliation: Dipartimento di Scienze Agro-alimentari, Ambientali e Animali, University of Udine, Via delle Scienze 208, 33100, Udine, Italy. simone.castellarin@ubc.ca.|Wine Research Centre, The University of British Columbia, 2205 East Mall, Vancouver, BC, V6T 1Z4, Canada. simone.castellarin@ubc.ca.
authors.forename: Simone D
authors.initials: SD
authors.lastname: Castellarin
mesh_terms: D055864:Droughts; D005638:Fruit / Q000378:metabolism; D020869:Gene Expression Profiling; D055432:Metabolomics; D010666:Phenylpropionates / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism*; D064210:Secondary Metabolism; D013729:Terpenes / Q000378:metabolism*; D027843:Vitis / Q000378:metabolism*
chemical_list: D010666:Phenylpropionates; D010940:Plant Proteins; D013729:Terpenes
keywords: Abiotic stress; Grapevine; Network analysis; RNA sequencing; Transcriptomics; Water deficit