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Identification and characterization of genes involved in stilbene biosynthesis and modification in grapevine
Vitis vinifera is an economically important plant that has been cultivated by mankind for thousands of years. The products of this plant, most prominently wine, are not only enjoyed by humans but are also beneficial to their health. This is in parts attributed to a group of phenolic secondary metabolites, the stilbenes. Due to their anti-oxidative, anti-inflammatory, anti-carcinogenic and anti-aging properties, it is thought that they might potentially help preventing cardiovascular diseases and help e.g. in cancer treatment. In the plants that naturally produce stilbenes, they are active during biotic stresses including defenses against bacteria, viruses, microbes and fungi as well as in response to abiotic stresses like mechanical injury or UV-exposure. Plants accumulate stilbenes in significant amounts not only in vegetative parts, but also in fruits, which are used as food or in the production of juices and wines.
Similar to other polyphenols like flavonoids and lignins, stilbenes are produced from precursors from the phenylpropanoid pathway with the first specific enzyme being the stilbene synthase. It has been shown that in different plants there is a huge variety of different stilbenes, which have distinct functions. This large variety of stilbenes is achieved by modifying the “basic” stilbene unit resveratrol. Modifications include, amongst others, oxidation, polymerization, glycosylation or methoxylation. Previous studies showed that the transcription factors VvMYB14 and VvMYB15 play an essential role in the regulation of the stilbene biosynthesis and modification pathway.
It has been shown that specific modified stilbenes like pterostilbene or viniferin are potentially more toxic e.g. to certain fungi or are produced specifically in infection situations. Although, in the current views of politics and society, the modifying or regulating genes cannot be introduced into interesting grapevine-varieties artificially, knowledge about them could at least help traditional breeding efforts.
Furthermore, the mentioned health beneficial properties make them interesting for companies in the health and cosmetic sector, which is shown by the already wide variety of products containing either for example grape extract or even specifically resveratrol, which is already produced in Saccharomyces cerevisiae.
In order to identify enzymes that are involved in the modification of stilbenes in grapevine, the knowledge about the two transcription factors (VvMYB14 and VvMYB15) was used to screen for appropriate candidate genes in a micro array. The aim of this project is to not only show the gene expression in correlation to the metabolite accumulation for example during grape berry ripening or leaf infection, but also to show their substrate- and product specificity in enzymatic assays.