Proceedings of the XLVI Italian Society of Agricultural Genetics - SIGA Annual Congress
Giardini Naxos, Italy - 18/21 September, 2002
STILBENES AND FLAVONOIDS IN GRAPEVINE: GENES EXPRESSION IN BERRIES TREATED WITH ABA AND SUGARS
RICCOMAGNO N.*, SCHUBERT A.**
*) Dipartimento di Colture Arboree, Università di Torino, 10095 Grugliasco (TO), Italy
**) Istituto Virologia Vegetale-CNR, Sezione Viticoltura, 10095 Grugliasco (TO), Italy
Vitis, ABA, sugars, flavonoid, resveratrol
Flavonoids and stilbenes (resveratrol and viniferin) are important plant secondary metabolites involved in many plant process. These compounds possess antioxidant activity, and the potential health benefit of red wine might be because of this property.
Although the genetic manipulation of plants to improve the composition of health-promoting phytochemicals has been proposed, a major limitation has been the lack of knowledge regarding the complete biosynthetic pathways needed for the synthesis and the regulation of expression of this genes.
The berries of Vitis vinifera accumulate large concentration of flavonoids in their skin (epicarp) during ripening, in particular anthocyanins, and in this period the expression of most of the known biosynthetic genes in enhanced.
Berries of several red-coloured grape varieties were sprayed with 1000 ppm ABA in 50% ethanol, the same are also incubated by their severed pedicel in 100 ppm ABA solutions. Sugar treatments consisted in incubating berry skins in 0.3 M solutions of glucose, fructose and sucrose. Using skins cDNA, we investigated the expression of the following genes: CHS (chalcone synthase), CHI (chalcone isomerase), F3H (flavanone 3-hydroxylase), DFR (dihydroflavonol reductase), LDOX (leucoanthocyanidin dioxygenase), UFGT (UDP-glucose-flavonoid glucosyl transferase), and StSy (stilbene synthase). The mRNA levels were determined in berries treated before and at veraison.
The results obtained after spraying berries with ABA before veraison show that the expression of most of the tested flavonoid biosynthetic genes increase by a factor of two; at veraison the concentration of transcripts increase by a factor of four. On the contrary, StSy expression increased in green berries but not at veraison. Incubation of berries in ABA solution did not affect the expression of either groups of genes.
The analysis of the expression of genes before veraison in response to sugars shows that glucose treatment increases the expression of CHS, CHI, F3H and DFR, but not of the other flavonoid biosynthetic genes. Sucrose treatment increases the expression of CHS. The analysis of sugar concentrations in same samples shows that the added sucrose was nearly completely hydrolyzed to hexoses. At veraison, the expression of these genes was not modified by treatments with sugars. StSy followed a different pattern: before veraison expression was enhanced after incubation with sucrose, while at veraison expression decreased following all sugar treatments.