title: Functional diversification of grapevine MYB5a and MYB5b in the control of flavonoid biosynthesis in a petunia anthocyanin regulatory mutant.
abstract: Flavonoids play a key role in grapevine physiology and also contribute substantially to the quality of berries and wines. VvMYB5a and VvMYB5b are R2R3-MYB transcription factors previously proposed to control the spatiotemporal expression of flavonoid structural genes during berry development. We investigated the functions of these two proteins in detail by heterologous expression in a petunia an2 mutant, which has negligible anthocyanin levels in the petals because it lacks the MYB protein PhAN2. We also expressed VvMYBA1, the grapevine ortholog of petunia PhAN2, in the same genetic background. The anthocyanin profiles induced by expressing these transgenes in the petals revealed that VvMYBA1 is the functional ortholog of PhAN2 and that, unlike VvMYB5a, VvMYB5b can partially complement the an2 mutation. Transcriptomic analysis of petals by microarray hybridization and quantitative PCR confirmed that VvMYB5b up-regulates a subset of anthocyanin structural genes, whereas VvMYB5a has a more limited impact on the expression of genes related to anthocyanin biosynthesis. Furthermore, we identified additional specific and common targets of these two regulators, related to vacuolar acidification and membrane remodeling. Taken together, these data provide insight into the role of VvMYB5a and VvMYB5b in flavonoid biosynthesis and provide evidence for additional regulatory roles in distinct pathways.
authors.affiliation: Department of Biotechnology, University of Verona, Strada Le Grazie 15, 37134 Verona, Italy.
authors.forename: Erika
authors.initials: E
authors.lastname: Cavallini
authors.forename: Sara
authors.initials: S
authors.lastname: Zenoni
authors.forename: Laura
authors.initials: L
authors.lastname: Finezzo
authors.forename: Flavia
authors.initials: F
authors.lastname: Guzzo
authors.forename: Anita
authors.initials: A
authors.lastname: Zamboni
authors.forename: Linda
authors.initials: L
authors.lastname: Avesani
authors.forename: Giovanni Battista
authors.initials: GB
authors.lastname: Tornielli
mesh_terms: D000872:Anthocyanins / Q000378:metabolism*; D005419:Flavonoids / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D032306:Petunia / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D027843:Vitis / Q000235:genetics / Q000378:metabolism*
chemical_list: D000872:Anthocyanins; D005419:Flavonoids; D014157:Transcription Factors
keywords: Flavonoid pathway; MYB transcription factors; Petunia hybrida; Transcriptomics; Vitis vinifera