Postharvest treatments with ethylene on Vitis vinifera (cv Sangiovese) grapes affect berry metabolism and wine composition.

Grapes (Vitis vinifera, cv Sangiovese), harvested at standard commercial maturity, were treated for 36 h with ethylene (ET, 1000 ppm) or air (control, CT) before vinification. The composition of the grapes, must and wine was different in the CT and ET samples. In the ET wine, higher concentrations of specific phenol compounds, belonging to the classes of flavonols, anthocyanins, flavan-3-ols, and stilbenes, were detected. ET induced a significant change in the wine aroma profile by increasing free volatile categories such as phenols and fatty acids, and reducing the content of carbonyl compounds and, in particular, of esters. Less pronounced differences between CT and ET wines were observed in terms of glycosidically-bound volatile compounds. The activity of pectin methyl esterase and ß-glucosidase was enhanced in ET-treated berry skins, suggesting that cell wall properties and changes in the hydrolytic activity are effective in modulating the composition of CT and ET wines.

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 CO(2) and then transferred to air for an additional 9 days to partially dehydrate (about 20% weight loss). At the end of the CO(2) 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 CO(2) 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.

Solar UV-B radiation influences carotenoid accumulation of tomato fruit through both ethylene-dependent and -independent mechanisms.

The effect of UV-B shielding on ethylene production in ripening tomato fruits and the contribution of ethylene and UV-B radiation on carotenoid accumulation and profile during ripening were assessed to get more insight about the interplay between these two regulatory factors. To this aim, rin and nor tomato mutants, unable to produce ripening ethylene, and cv Ailsa Craig were cultivated under control or UV-B depleted conditions until full fruit ripening. The significantly decreased ethylene evolution following UV-B depletion, evident only in Ailsa Craig, suggested the requirement of functional rin and nor genes for UVB-mediated ethylene production. Carotenoid content and profile were found to be controlled by both ethylene and UV-B radiation. This latter influenced carotenoid metabolism either in an ethylene-dependent or -independent way, as indicated by UVB-induced changes also in nor and rin carotenoid content and confirmed by correlation plots between ethylene evolution and carotenoid accumulation performed separately for control and UV-B shielded fruits. In conclusion, natural UV-B radiation influences carotenoid metabolism in a rather complex way, involving ethylene-dependent and -independent mechanisms, which seem to act in an antagonistic way.