As a result of natural hybridization and human selection over millennia, the skin colors of grapes have become greatly diversified. The color is determined by the quantity and composition of anthocyanins. Color-skinned cultivars accumulate anthocyanins in their skins, whereas white-skinned cultivars do not. Myb-related transcription-factor genes such as VvmybA1 regulate anthocyanin biosynthesis. VvMYBA2r, VlmybA1-1, VlmybA1-2, and VlmybA2, which are homologs of VvmybA1, also regulate anthocyanin biosynthesis. In this study, we isolated a novel Myb-related sequence, VlmybA1-3, from cultivars of Vitis labruscana (Vitis vinifera x Vitis labrusca) by means of inverse PCR, and confirmed by means of transient gene expression assay that the gene regulates anthocyanin biosynthesis in grape berry skin. Seedlings of V. labruscana with two functional haplotypes at a region of berry color loci accumulated more anthocyanins than seedlings with a single functional haplotype. In addition, we investigated the haplotypes at the region in 35 cultivars (both V. vinifera and V. labruscana), and found certain typical characteristics. These findings will contribute to the selection of seedlings with high anthocyanin quantities in breeding programs for wine and table grapes, and will help elucidate the origin and evolution of Vitis species.

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Skin color is one of the most important fruit traits in grape, and has become greatly diversified due to hybridization and human selection. Many studies concerning the genetic control of grape color in European species (Vitis vinifera L.), especially the role of MYB-related genes, have been reported. On the other hand, there have been few studies of the MYB-related genes in grapes belonging to V. ×labruscana L.H. Bailey, a subgroup of grapes that originated from the hybridization of V. labrusca with V. vinifera. In the present study, we found a novel functional haplotype, HapE2 (consisting of the genes VlMYBA2 and VlMYBA1-3), in diploid V. ×labruscana. Moreover, we developed a method to determine the haplotype compositions of tetraploid grapes by means of quantitative real-time PCR, and investigated the relationship between haplotype composition and skin color. The color locus in V. ×labruscana grapes usually consists of functional haplotypes (HapE1 and/or HapE2), and non-functional haplotype HapA. The number of functional haplotypes in the genome was found to be correlated with the level of anthocyanin in the skin. Anthocyanin contents of grapes that contained HapE2 were significantly higher than those containing HapE1. These results suggest that the number and kind of functional haplotypes at the color locus are the major genetic factors that determine skin color variation. These findings provide new knowledge about the unique genetic control of color in V. ×labruscana grapes, and should contribute to development of new cultivars that have the desired color and anthocyanin content.

A white-wine grape, Pinot Blanc, is thought to be a white-skinned mutant of a red-wine grape, Pinot Noir. Pinot Noir was heterozygous for VvmybA1. One allele was the non-functional VvmybA1a, and the other was the functional VvmybA1c. In Pinot Blanc, however, only VvmybA1a was observed, and the amount of VvmybA1 DNA in Pinot Blanc was half that in Pinot Noir. These findings suggest that deletion of VvmybA1c from Pinot Noir resulted in Pinot Blanc.

The main polyphenols were isolated from the leaves of six selected persimmon cultivars. Seven compounds were obtained by reverse-phase HPLC, and their structures were elucidated by multiple NMR measurements. These compounds are hyperoside, isoquercitrin, trifolin, astragalin, chrysontemin, quercetin-3-O-(2''-O-galloyl-β-D-glucopyranoside) (QOG), and kaempferol-3-O-(2''-O-galloyl-β-D-glucopyranoside) (KOG). Their inhibitory activity was tested against tyrosinase for the oxidation of L-DOPA, and only chrysontemin showed inhibitory activity. To investigate the differences of their inhibitory effects, the tyrosinase inhibitory activities of their aglycons, cyanidin, quercetin, and kaempferol, were also tested. As a result, it was confirmed that the most influential moiety for tyrosinase inhibition was the 3',4'-dihydroxy groups of the catechol moiety. Moreover, the tyrosinase inhibitory activity of chrysontemin, which was identified in persimmon leaves for the first time, is supported by a simulated model of chrysontemin docking into mushroom tyrosinase.