title: The grapevine VvibZIPC22 transcription factor is involved in the regulation of flavonoid biosynthesis.
abstract: In grapevine, flavonoids constitute one of the most abundant subgroups of secondary metabolites, influencing the quality, health value, and typicity of wines. Their synthesis in many plant species is mainly regulated at the transcriptional level by modulation of flavonoid pathway genes either by single regulators or by complexes of different regulators. In particular, bZIP and MYB factors interact synergistically in the recognition of light response units present in the promoter of some genes of the pathway, thus mediating light-dependent flavonoid biosynthesis. We recently identified VvibZIPC22, a member of clade C of the grapevine bZIP family, in a quantitative trait locus (QTL) specifically associated with kaemperol content in mature berries. Here, to validate the involvement of this candidate gene in the fine regulation of flavonol biosynthesis, we characterized its function by in vitro and in vivo experiments. A role for this gene in the control of flavonol biosynthesis was indeed confirmed by its highest expression at flowering and during UV light-mediated induction, paralleled by accumulation of the flavonol synthase 1 transcript and flavonol compounds. The overexpression of VvibZIPC22 in tobacco caused a significant increase in several flavonoids in the flower, via induction of general and specific genes of the pathway. In agreement with this evidence, VvibZIPC22 was able to activate the promoters of specific genes of the flavonoid pathway, alone or together with other factors, as revealed by transient reporter assays. These findings, supported by in silico indications, allowed us to propose VvibZIPC22 as a new regulator of flavonoid biosynthesis in grapevine.
authors.affiliation: Research and Innovation Centre, Fondazione Edmund Mach, Via E. Mach 1, 38010 S. Michele all'Adige, Trento, Italy giulia.malacarne@fmach.it.
authors.forename: Giulia
authors.initials: G
authors.lastname: Malacarne
authors.affiliation: Research and Innovation Centre, Fondazione Edmund Mach, Via E. Mach 1, 38010 S. Michele all'Adige, Trento, Italy.
authors.forename: Emanuela
authors.initials: E
authors.lastname: Coller
authors.affiliation: Centre for Organismal Studies Heidelberg, University of Heidelberg, Im Neuenheimer Feld 360, D-69120 Heidelberg, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Czemmel
authors.affiliation: Research and Innovation Centre, Fondazione Edmund Mach, Via E. Mach 1, 38010 S. Michele all'Adige, Trento, Italy.
authors.forename: Urska
authors.initials: U
authors.lastname: Vrhovsek
authors.affiliation: Research and Innovation Centre, Fondazione Edmund Mach, Via E. Mach 1, 38010 S. Michele all'Adige, Trento, Italy.
authors.forename: Kristof
authors.initials: K
authors.lastname: Engelen
authors.affiliation: Research and Innovation Centre, Fondazione Edmund Mach, Via E. Mach 1, 38010 S. Michele all'Adige, Trento, Italy.
authors.forename: Vadim
authors.initials: V
authors.lastname: Goremykin
authors.affiliation: Centre for Organismal Studies Heidelberg, University of Heidelberg, Im Neuenheimer Feld 360, D-69120 Heidelberg, Germany Studiengang Weinbau und Oenologie, Dienstleistungszentrum Laendlicher Raum Rheinpfalz, Breitenweg 71, D-67435 Neustadt, Germany.
authors.forename: Jochen
authors.initials: J
authors.lastname: Bogs
authors.affiliation: Research and Innovation Centre, Fondazione Edmund Mach, Via E. Mach 1, 38010 S. Michele all'Adige, Trento, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Moser
mesh_terms: D044948:Flavonols / Q000096:biosynthesis / Q000235:genetics*; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D027843:Vitis / Q000235:genetics* / Q000378:metabolism
chemical_list: D044948:Flavonols; D010940:Plant Proteins; D014157:Transcription Factors
keywords: bZIP factors; co-expression analysis; flavonoids; gene expression; grapevine; luciferase assay; metabolic profiling; tobacco; transient expression.