WRKY transcription factors and regulation of the stilbene biosynthetic pathway in grapevine: new insights and perspectives

Stilbene synthase (STS) is the key enzyme leading to the biosynthesis of resveratrol and belongs to the type III polyketide synthase super family, of which chalcone synthase (CHS) represents the archetypal enzyme. Recently we reported the identification and functional characterization of two grapevine MYB transcription factors (TFs) that appear to regulate the stilbene biosynthetic pathway. These TFs, designated VvMYB14 and VvMYB15, strongly co-express with VvSTS genes under a range of stress-induced conditions and in developmentally regulated tissues. In transient gene reporter assays, these TFs were demonstrated to specifically activate the promoter of two VvSTS genes and the ectopic expression of VvMYB15 in grapevine hairy roots resulted in VvSTSs increased expression and in the accumulation of piceid in planta. However, despite these significant advances, many questions remain to be answered regarding the grapevine biosynthetic pathway. Based on the notion that genes involved in similar or related processes may exhibit similar expression patterns over a range of experimental conditions, we performed a co-expression network analysis on different grapevine gene expression datasets in order to identify candidate TFs belonging to the WRKY family, possibly involved in the regulation of the stilbene biosynthetic pathway. These genes scored correlation values with VvSTSs even higher than those observed for VvMYB14 and VvMYB15, and proved to be induced in response to the same biotic stresses found responsible for VvSTS induction.