Anthocyanidin Reductase Gene Expression and Accumulation of Flavan-3-ols in Grape Berry

Abstract

Proanthocyanidins, which are polymers and oligomers of flavan-3-ol units, are important components of grape for red winemaking and accumulate in the berry skins and seeds. Major flavan-3-ol units of grape proanthocyanidins are (-)-epicatechin and (-)-epigallocatechin. It was recently reported that (-)-epicatechin and (-)-epigallocatechin were biosynthesized from corresponding anthocyanidins by anthocyanidin reductase (ANR). In the current study, we obtained a genomic sequence of the ANR gene of Vitis vinifera cv. Cabernet Sauvignon (VvANR). The deduced amino acid sequence of VvANR conserved the characteristic sequence of ANR of other plants. Southern blot analysis showed that grape ANR is probably encoded by a single copy gene in its haploid genome. Real-time quantitative-PCR using berry skins and seeds showed that the mRNA of VvANR accumulates at the early stage of berry development and then decreases toward the ripening stage. Our analysis and other reports show that proanthocyanidins accumulate in the berry skins and seeds before veraison, especially during the early stage of development, and then decrease in concentration during ripening. Thus, the change of mRNA accumulation substantially coincides with the change of proanthocyanidin accumulation in the berry skins and seeds. These results indicate that at least a part of (-)-epicatechin and (-)-epigallocatechin biosynthesis is probably controlled by the transcription of VvANR.