The R2R3-MYB Transcription Factors MYB14 and MYB15 Regulate Stilbene Biosynthesis in Vitis vinifera

Abstract

Plant stilbenes are phytoalexins that accumulate in a small number of plant species, including grapevine (Vitis vinifera), in response to biotic and abiotic stresses and have been implicated in many beneficial effects on human health. In particular, resveratrol, the basic unit of all other complex stilbenes, has received widespread attention because of its cardio-protective, anticarcinogenic, and antioxidant properties. Although stilbene synthases (STSs), the key enzymes responsible for resveratrol biosynthesis, have been isolated and characterized from several plant species, the transcriptional regulation underlying stilbene biosynthesis is unknown. Here, we report the identification and functional characterization of two R2R3-MYB-type transcription factors (TFs) from grapevine, which regulate the stilbene biosynthetic pathway. These TFs, designated MYB14 and MYB15, strongly coexpress with STS genes, both in leaf tissues under biotic and abiotic stress and in the skin and seed of healthy developing berries during maturation. In transient gene reporter assays, MYB14 and MYB15 were demonstrated to specifically activate the promoters of STS genes, and the ectopic expression of MYB15 in grapevine hairy roots resulted in increased STS expression and in the accumulation of glycosylated stilbenes in planta. These results demonstrate the involvement of MYB14 and MYB15 in the transcriptional regulation of stilbene biosynthesis in grapevine.

Regulation of stilbene biosynthesis in plants

“…Fang et al (2014) showed that the variation in expression of MYB14 correlated with the variation in resveratrol content in two grapevine cultivars (Vitis monticola 9 Vitis riparia with a high resveratrol content and V. vinifera with a low resveratrol content). In addition, Fang et al (2014) confirmed the data by Höll et al (2013) that the expression patterns of MYB14 and STS were almost identical under UV-C treatment. Using a one-hybrid yeast assay, they also found that MYB14 directly interacts with the STS promoter (Box-L5 motif) in vitro.…”

“…Cell suspensions of V. vinifera and tobacco leaves transiently expressing STS luciferase reporter constructs showed considerable induction of the STS29 and STS41 promoter activities when co-transformed with MYB14 and MYB15. To confirm the involvement of these TFs in the regulation of stilbene biosynthesis in planta, Höll et al (2013) obtained grapevine hairy roots overexpressing MYB15 and revealed that an increased accumulation of t-piceid was coupled to the up-regulation of STS29 and STS41 transcription levels in the hairy root line. Taken together, the results by Höll et al (2013) indicated that MYB14 and MYB15 TFs are involved in the induction of STS29 and STS41 transcription in V. vinifera.…”

“…To confirm the involvement of these TFs in the regulation of stilbene biosynthesis in planta, Höll et al (2013) obtained grapevine hairy roots overexpressing MYB15 and revealed that an increased accumulation of t-piceid was coupled to the up-regulation of STS29 and STS41 transcription levels in the hairy root line. Taken together, the results by Höll et al (2013) indicated that MYB14 and MYB15 TFs are involved in the induction of STS29 and STS41 transcription in V. vinifera. Fang et al (2014) showed that the variation in expression of MYB14 correlated with the variation in resveratrol content in two grapevine cultivars (Vitis monticola 9 Vitis riparia with a high resveratrol content and V. vinifera with a low resveratrol content).…”

“…Höll et al (2013) identified and characterized two R2R3-MYB-type TFs MYB14 and MYB15 of V. vinifera that positively regulate the stilbene biosynthetic pathway. According to the results obtained, these TFs strongly co-express with certain STS genes in different organs of V. vinifera in response to UV-C irradiation, wounding, and downy mildew infection.…”

Transcriptome pathways in leaf and root of grapevine genotypes with contrasting drought tolerance

“…Stilbenoids (resveratrol in particular) are powerful defence antioxidant molecules found in several species and their accumulation is particularly high in grapevine (Vannozzi et al, 2012;Höll et al, 2013;Stuart and Robb, 2013). Furthermore, it has been suggested that flavonoids, whose biosynthetic genes are induced only in M4 leaves under WS ( Figure 3B), act as antioxidants in plant response to oxidative stresses (Brunetti et al, 2013).…”