Stilbene biosynthesis pathway of the grapevine

Vitisvinifera is an economically important plant that has been cultivated by humans for thousands of years. The products of this plant—most notably wine—are not only enjoyed by people but also promote good health. This is due, in part, to a group of phenolic secondary metabolites known as stilbenes. Due to their antioxidant, anti-inflammatory, anticarcinogenic, and anti-aging effects, it is believed that they could potentially help prevent cardiovascular diseases or be used in cancer therapy. In plants that produce stilbenes, these compounds are active during biotic stress situations. This includes, for example, defense against bacteria, viruses, microbes, and fungi. Furthermore, they also help the plant respond to abiotic stress factors such as mechanical damage or UV radiation. Plants accumulate stilbenes in significant quantities not only in their vegetative parts but also in fruits used in the production of food, juices, and wine.

Like other polyphenols, such as flavonoids or lignins, stilbenes are formed from precursors in the phenylpropanoid biosynthetic pathway. The first stilbene-specific enzyme in this process is stilbene synthase. It has been shown in various plants that there is a wide variety of stilbenes, each with different functions. This wide variety is achieved through chemical modifications of the “basic” compound, resveratrol. These modifications include, among others, oxidation, polymerization, glycosylation, or methoxylation. Previous studies have shown that the transcription factors VvMYB14 and VvMYB15 play an essential role in regulating the stilbene biosynthetic pathway and these modifications.

It has been shown that specific, modified stilbenes, such as pterostilbene or viniferin, are potentially more toxic to fungi or are produced specifically in response to infection. Although current political and societal views make it impossible to artificially introduce modifying or regulatory genes into grapevines, this knowledge can nevertheless benefit conventional breeding. Furthermore, the aforementioned health-promoting effects of stilbenes make them of interest to companies in the health and cosmetics sectors, where a wide range of products containing either grapevine extracts or specifically resveratrol is already in sales. This is currently produced in yeast (Saccharomycescerevisiae).

To identify the enzymes involved in the modification of stilbenes, knowledge of the two transcription factors (VvMYB14 and VvMYB15) was used to search for candidate genes in a microarray. The goal of this project is not only to demonstrate a correlation between gene expression and the accumulation of the corresponding metabolites during berry ripening and in the presence of an infection, but also to establish the substrate and product specificity of the enzymes.