title: Ectopic expression of VvMybPA2 promotes proanthocyanidin biosynthesis in grapevine and suggests additional targets in the pathway.
abstract: Grapevine (Vitis vinifera) proanthocyanidins contribute to plant defense mechanisms against biotic stress and also play a critical role in organoleptic properties of wine. In grapevine berry, these compounds are mainly accumulated in exocarps and seeds in the very early stages of development. A previous study has already identified VvMybPA1 as the first transcription factor involved in the regulation of the proanthocyanidin pathway during seed development in grapevine. A novel Myb factor, VvMybPA2, which is described in this study, is in contrast mainly expressed in the exocarp of young berries and in the leaves. This transcription factor shows very high protein sequence homology with other plant Myb factors, which regulate flavonoid biosynthesis. Ectopic expression of either VvMybPA1 or VvMybPA2 in grapevine hairy roots induced qualitative and quantitative changes of the proanthocyanidin profiles. High-throughput transcriptomic analyses of transformed grapevine organs identified a large set of putative targets of the VvMybPA1 and VvMybPA2 transcription factors. Both genes significantly activated enzymes of the flavonoid pathway, including anthocyanidin reductase and leucoanthocyanidin reductase 1, the specific terminal steps in the biosynthesis of epicatechin and catechin, respectively, but not leucoanthocyanidin reductase 2. The functional annotation of the genes whose expression was modified revealed putative new actors of the proanthocyanidin pathway, such as glucosyltransferases and transporters.
authors.affiliation: UMR SPO 1083, Campus SupAgro-INRA, F-34060 Montpellier, France. terrier@supagro.inra.fr
authors.forename: Nancy
authors.initials: N
authors.lastname: Terrier
authors.forename: Laurent
authors.initials: L
authors.lastname: Torregrosa
authors.forename: Agnès
authors.initials: A
authors.lastname: Ageorges
authors.forename: Sandrine
authors.initials: S
authors.lastname: Vialet
authors.forename: Clotilde
authors.initials: C
authors.lastname: Verriès
authors.forename: Véronique
authors.initials: V
authors.lastname: Cheynier
authors.forename: Charles
authors.initials: C
authors.lastname: Romieu
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D000981:Antiprotozoal Agents / Q000378:metabolism*; D016384:Consensus Sequence; D018506:Gene Expression Regulation, Plant; D020570:Genes, myb; D020411:Oligonucleotide Array Sequence Analysis; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics*; D044945:Proanthocyanidins / Q000096:biosynthesis*; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic; D027843:Vitis / Q000235:genetics* / Q000378:metabolism
chemical_list: D000975:Antioxidants; D000981:Antiprotozoal Agents; D010940:Plant Proteins; D044945:Proanthocyanidins; D014157:Transcription Factors; C013221:proanthocyanidin