Leucoanthocyanidin Reductase Genes Research Articles

Isolation and expression of gene encoding leucoanthocyanidin reductase from Diospyros kaki during fruit development

Leucoanthocyanidin reductase (LAR) converts leucoanthocyanidin to (+)-catechin, a precursor of proanthocyanidins abundant in Japanese persimmon (Diospyros kaki Thunb.) fruits. A putative LAR gene (DkLAR) was isolated by rapid amplification of cDNA ends from young fruits. The full-length cDNA of DkLAR gene was 1 356 bp long and encoded an open reading frame of 349 residues. The deduced DkLAR protein was closely related to the homolog in other plant species. The expression of the DkLAR gene in Chinese pollination-constant non-astringent (PCNA) genotype was coincident with the tannin cell development, but was not in Japanese PCNA and Chinese pollination-variant astringent (PCA) genotypes.

Effect of Shading on Proanthocyanidin Biosynthesis in the Grape Berry

Proanthocyanidins, which are oligomers and polymers of flavan-3-ol units (e.g., (+)-catechin and (−)-epicatechin), are important components of grapes for red winemaking. Flavan-3-ols are biosynthesized by the catalysis of anthocyanidin reductase (ANR) and leucoanthocyanidin reductase (LAR). In this study, we investigated the effect of shading on proanthocyanidin biosynthesis in berries of Vitis vinifera ‘Cabernet Sauvignon’. Shading of the berries reduced the accumulation of proanthocyanidins and the transcription of ANR and LAR genes in the skins during berry development, while no significant effect was observed in the seeds. Because the proanthocyanidins significantly decreased in the skins and seeds of the control berries during ripening, the levels of proanthocyanidins were similar in the shaded and control berries at the harvest stage.

Proanthocyanidin Synthesis and Expression of Genes Encoding Leucoanthocyanidin Reductase and Anthocyanidin Reductase in Developing Grape Berries and Grapevine Leaves

Proanthocyanidins (PAs), also called condensed tannins, can protect plants against herbivores and are important quality components of many fruits. Two enzymes, leucoanthocyanidin reductase (LAR) and anthocyanidin reductase (ANR), can produce the flavan-3-ol monomers required for formation of PA polymers. We isolated and functionally characterized genes encoding both enzymes from grapevine (Vitis vinifera L. cv Shiraz). ANR was encoded by a single gene, but we found two highly related genes encoding LAR. We measured PA content and expression of genes encoding ANR, LAR, and leucoanthocyanidin dioxygenase in grape berries during development and in grapevine leaves, which accumulated PA throughout leaf expansion. Grape flowers had high levels of PA, and accumulation continued in skin and seeds from fruit set until the onset of ripening. VvANR was expressed throughout early flower and berry development, with expression increasing after fertilization. It was expressed in berry skin and seeds until the onset of ripening, and in expanding leaves. The genes encoding LAR were expressed in developing fruit, particularly in seeds, but had low expression in leaves. The two LAR genes had different patterns of expression in skin and seeds. During grape ripening, PA levels decreased in both skin and seeds, and expression of genes encoding ANR and LAR were no longer detected. The results indicate that PA accumulation occurs early in grape development and is completed when ripening starts. Both ANR and LAR contribute to PA synthesis in fruit, and the tissue and temporal-specific regulation of the genes encoding ANR and LAR determines PA accumulation and composition during grape berry development.