Characterization and differential expression analysis of complete coding sequences of Vitis vinifera L. sirtuin genes.

The sirtuin/Sir2 (Silent information regulator 2) family of NAD+-dependent deacetylases and mono-ADP-ribosyltransferases plays an important role in several cellular processes including gene silencing, cell cycle regulation and life span extension in yeast and animals. Compared to other eukaryotes, plants have relatively fewer SIR2 related genes encoding only two putative SIR2 family proteins. Recently, two putative sirtuin genes were identified also in the grapevine genome. Starting from the predicted coding sequences present in the database, we have been able to obtain two truly expressed coding sequences from the start to the stop codon for both sirtuin genes that were named VvSRT1 and VvSRT2. The search for the expressed coding sequences was performed by comparing the predicted sequences with the recently available grape RNA seq database with the aim to develop the primers to be used in reverse transcriptase PCR reactions to amplify the genes of interest. Finally, in order to better understand the physiological role of both sirtuins, we investigated the expression of these genes in young leaves, mature leaves, and berries sampled at different growing stages. In leaves, usually it has been observed that VvSRT1 is less expresses than VvSRT2, moreover in young leaves VvSRT2 showed the higher expression during setting while in mature leaves during the flowering time. No particular variations have been observed concerning VvSRT1. In berries the two genes showed more similar expression level, and they showed the highest expression during the flowering time. Finally, the expression of VvSRT2 in berries is smaller than in leaves.

Role of viticultural factors on stilbene concentrations of grapes and wine.

Stilbenes are phenolics that can be found in different grapevine organs, such as berries, leaves, canes and roots. Stilbenes act as antifungal compounds since they are synthesized by the plant in response to pathogen attack. Other abiotic elicitors, such as ultraviolet rays and heavy metals, can trigger stilbene production. Many stilbenic compounds have been detected in grapes and wine (resveratrol, piceid, viniferins, astringin, etc.). The latest stilbene to be analyzed is piceatannol (or astringinin). Stilbene synthesis in grapes depends on different viticultural factors such as the grape variety, the environment and cultural practices. Concerning grape variety, red berry-grapes have higher stilbene levels than white berry-grapes. With regard to climate, preliminary results suggest a positive correlation between vineyard elevation and stilbene grape concentrations. Quality-oriented cultural practices produce grapes with high levels of stilbenes.

Stilbene compounds: from the grapevine to wine.

Stilbenes are natural compounds occurring in a number of plant families, including Vitaceae and (within this family) Vitis vinifera L., which is the most important species grown worldwide for grape and wine production. Stilbenes (resveratrol and viniferins) are present in grapevine as constitutive compounds of the woody organs (roots, canes, stems) and as induced substances (in leaves and fruit) acting as phytoalexins in the mechanisms of grape resistance against certain pathogens. Resveratrol (3, 5, 4'-trihydroxystilbene) was also detected in wine and it was thought to be the active principle of red wines that were shown to reduce heart diseases. This paper reviews data, obtained by the Viticulture Institute of the Catholic University at Piacenza and taken from the literature, on some aspects of stilbene physiology in grapevine and on their relation to resveratrol wine levels. Constitutive stilbene contents of woody organs are reported, as well as the possible role of cluster stems as a source of resveratrol for wine. The accumulation of stilbenes in grape berries infected by grey mould (Botrytis cinerea Pers.) has been investigated and the effects of environmental factors on resveratrol grape and wine levels will be discussed. An unidentified new hydroxystilbene was detected in wine.

Antiplatelet activity of cis-resveratrol.

The anti-aggregating effect of cis-resveratrol (cis-3,4,5- trihydroxystilbene) has been evaluated in vitro in different concentrations on platelet-rich plasma from health volunteers. Cis-resveratrol at the concentration of 1 x 10(-5) and 1 x 10(-6) M was able to decrease collagen-induced platelet aggregation by 43.5 +/-11.4% and 26.8 +/- 14.6%, while trans-resveratrol at the same concentration showed a slightly lower activity. In view of the behaviour of these two isomers in biological fluids, the evaluation of resveratrol activity in animals and humans take into account the total amount of the two isomers.