Phenol compound metabolism and gene expression in the skin of wine grape (Vitis vinifera L.) berries subjected to partial postharvest dehydration

Specific polyphenol compound concentrations and gene expression patterns were determined by both microarray and qRT-PCR analyses in the epicarp of red-skinned grape berries (Vitis vinifera L. cv ‘Raboso Piave’) dehydrated, after harvest, at slow (S) and rapid (R) rates of up to 10 and 30% weight loss (WL). Increases in flavonols (quercetin) and trans-resveratrol concentrations were observed in the skins of all dehydrated samples, whereas flavan-3-ols concentrations showed a decreasing trend, which was more pronounced in S samples. The decrease in flavan-3-ol concentrations was paralleled by a reduction in procyanidin B1 and, particularly B2. Computational analysis of microarray data revealed that several key genes of the flavonoid pathways were unaffected or down-regulated during berry ehydration, with the exception of flavonol synthase, which was induced as well as one MybB transcription factor. Chalcone synthase (CHS), flavanone 3-hydroxylase (F3H), leucoanthocyanidin dioxygenase (LDOX) and MybA were markedly down-regulated, particularly in relation to 30% WL, whereas UDP-glucose:flavonoid 3-Oglucosyltransferase (UFGT) was unaffected in all the samples considered. Specific genes involved in the lignin biosynthetic pathway, including laccase, were induced in the most dehydrated samples. Considering the accumulation pattern and gene expression profiles, stilbenes and flavonols may represent useful biomarkers to monitor postharvest dehydration

Short-Term Postharvest Carbon Dioxide Treatments Induce Selective Molecular and Metabolic Changes in Grape Berries

Detached wine grapes (Vitis vinifera cv. 'Trebbiano', white skinned) were treated for 3 days with 30 kPa of CO2 and then transferred to air for an additional 9 days to partially dehydrate (about 20% weight loss). At the end of the CO2 treatment on withering berries, total polyphenols and flavonoids were maintained in the skin, but to a more limited extent in the pulp. An induction of the proanthocyanidin synthesis appeared to be one of the responses to the treatment because both (+)-catechin and (−)-epicatechin concentrations increased in the skin. The skin and pulp of the grape berries showed different molecular responses to a high CO2 treatment. As revealed by microarray hybridizations, 217 and 75 genes appeared differentially expressed in the skin and pulp of treated samples, respectively. Functional categorization and gene enrichment analyses pointed out that epicarp cells undergo more pronounced changes in transcript profiling at the end of the incubation period. Highly represented categories in both tissues were related to protein, stress, transcript, RNA, and hormone (ethylene, ABA) metabolism. Fermentation, CHO metabolism, and redox regulation functional categories were represented only in the skin

Effects of Postharvest Elicitors on Ripening-Related Metabolic Processes of Sangiovese Berries

With the aim of better understanding basic processes of Sangiovese berry ripening and considering that postharvest manipulation (to produce special wines as \u201cpassiti\u201d and/or reinforced) is now possible in environmentally-controlled dehydration tunnels where specific treatments can be easily performed, trials using two gaseous elicitors (carbon dioxide and ethylene) have been carried out on Sangiovese berries. The effects of CO2 treatment (30% v/v for 3 days followed by storage in air up to 9 days) have been evaluated on flesh and skin separately in terms of both transcript profiling, using the Aros V1 grape microarray (Operon, 14,562 oligos), and polyphenol content. At the end of the treatment and compared with berries at harvest, 214 and 107 targets resulted differentially expressed in the skin and pulp, respectively. This clearly indicates the different metabolic reactivity of the two tissues to environmental stimuli. BLASTX analysis assigned a putative function to 144 (skin) and 107 (pulp) differentially expressed targets. GO categories with the highest number of sequences were: Interaction with the Environment, Cell rescue defence and virulence, Protein with binding function, (primary and secondary) metabolism. Biochemical analyses pointed out that the presence of a CO2-enriched atmosphere after harvest affects polyphenol content: in fact, total phenol and , in particular flavan-3-ols concentration increased in skins of treated berries. These data clearly demonstrate that physiological-metabolic changes occur in Sangiovese berries following the postharvest treatment with CO2: some of these changes might be beneficial in terms of disease control (an important aspect for wine grapes undergoing postharvest dehydration and for the storage of table grapes) and antioxidant properties of the resulting wines. A similar methodological approach has been used for the evaluation of the effects of postharvest ethylene treatments (1000 ppm for 3 days followed by storage in air for 9 days): preliminary analyses pointed out a decrease of pectin content indicating an effect of the hormone on cell wall and on the extractability index. Considering polyphenols, stilbenic compounds (trans-resveratrol) appeared to increase in skins of ethylene-treated berries. This work has been financially supported by the Fondazione Cassa di Risparmio di Pisa

Effects of Postharvest Partial Dehydration and Prolonged Treatments with Ethylene on Transcript Profiling in Skins of Wine Grape Berries

or certain food products, postharvest controlled stresses or treatments with specific elicitors are applied to induce desired physical/chemical changes and/or to positively affect phytochemical content. This is the case of wine grapes where both strategies, singularly applied or coupled, can be used to modulate berry composition and, as a consequence, affect wine quality traits. Since the knowledge of the effects of these postharvest treatments on berry metabolism and the regulation of gene expression is very limited, a large-scale transcriptome analysis has been carried out, using an oligo-based microarray (14,562 probes) on skins of wine grape (Vitis vinifera L.) berries subjected to dehydration, at different rates, up to 30% of weight loss or to ethylene treatment (500 ppm for 7 days) after harvest. A number of differentially expressed targets was detected following both treatments, indicating that grape berries are still reactive at advanced stages of postharvest dehydration and that ethylene induces marked changes in transcriptome after harvest also in non-climacteric fruit such as grape berries