title: Functional characterization of a new grapevine MYB transcription factor and regulation of proanthocyanidin biosynthesis in grapes.
abstract: A new regulator of proanthocyanidin (PA) biosynthesis in grapes was found by screening genes coordinately expressed with PA accumulation under different light conditions using a substantially improved method of serial analysis of gene expression (SuperSAGE). This R2R3-MYB transcription factor, VvMYBPAR, shows high protein sequence similarity with PA biosynthesis-regulating plant MYBs, such as VvMYBPA2 and TRANSPARENT TESTA2. Its transcript levels were relatively high in the skins of young berries, whereas the levels were higher in the seeds and at a maximum around veraison. In addition to its response to modified light conditions, the gene responded to abscisic acid application in the skins of cultured berries. Among the PA-specific branch genes, this transcript profile was not correlated with that of VvANR and VvLAR1 but was closely related to that of VvLAR2, suggesting different regulation of PA-specific branch genes from that of a known PA regulator, VvMYBPA2. The PA-specific regulation of VvMYBPAR was confirmed by VvMYBPAR constitutive expression in Arabidopsis in which the transgene specifically induced PA biosynthetic genes and resulted in PA accumulation in plants grown on sucrose-supplemented media to induce anthocyanin synthesis. A transient reporter assay using grapevine cells showed that VvMYBPAR activated the promoters on PA-specific branch genes and candidate genes associated with modification and transport of monomeric PA precursors, as well as the promoters of VvCHS3 and VvF3'5'Hd in the common flavonoid pathway, but not that of VvUFGT on the anthocyanin-specific branch. This new factor suggests the polygenic regulation of PA biosynthesis in grapes by closely related MYB transcription factors.
authors.affiliation: National Research Institute of Brewing, 3-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046, Japan koyama@nrib.go.jp.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Koyama
authors.affiliation: National Research Institute of Brewing, 3-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046, Japan.
authors.forename: Mineyo
authors.initials: M
authors.lastname: Numata
authors.affiliation: National Institute of Fruit Tree Science, National Agriculture and Food Research Organization, 2-1 Fujimoto, Tsukuba, Ibaraki 305-8605, Japan.
authors.forename: Ikuko
authors.initials: I
authors.lastname: Nakajima
authors.affiliation: National Research Institute of Brewing, 3-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046, Japan.
authors.forename: Nami
authors.initials: N
authors.lastname: Goto-Yamamoto
authors.affiliation: Research Institute of Human and Environmental Science, Shinshu University, 3-15-1 Tokida, Ueda, Nagano 386-8567, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Matsumura
authors.affiliation: Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, 1-4-2 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527, Japan.
authors.forename: Nobukazu
authors.initials: N
authors.lastname: Tanaka
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D044945:Proanthocyanidins / Q000096:biosynthesis*; D011401:Promoter Regions, Genetic; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D027843:Vitis / Q000235:genetics / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D044945:Proanthocyanidins; D014157:Transcription Factors; C013221:proanthocyanidin
keywords: Abiotic stress; MYB transcription factor superfamily; SuperSAGE; Vitis vinifera.; abscisic acid; photoprotection; polygenic regulatory mechanism; proanthocyanidin biosynthesis; secondary metabolism; transcriptomics