The potato R locus codes for dihydroflavonol 4-reductase

Abstract

The potato R locus is required for the production of red pelargonidin-based anthocyanin pigments in potato (Solanum tuberosum L.). Red color also requires tissue-speciWc regulatory genes, such as D (for expression in tuber skin) and F (expression in Xowers). A related locus, P, is required for production of blue/purple anthocyanins; P is epistatic to R. We have previously reported that the dihydroXavonol 4-reductase gene (dfr) co-segregates with R. To test directly whether R corresponds to dfr, we placed the allele of dfr associated with red color under the control of the CaMV 35S promoter and introduced it into the potato cultivar Prince Hairy (genotype dddd rrrr P-), which has white tubers and pale blue Xowers. Transgenic Prince Hairy tubers remained white, but Xower color changed to purple. Three independent transgenic lines, as well as a vectortransformed line, were then crossed with the red-skinned variety Chieftain (genotype D-R-pppp), to establish populations that segregated for D, R, P, and the dfr transgene or empty vector. Markers were used to genotype progeny at D and R. Progeny carrying the empty vector in the genetic background D-rrrr produced white or purple tubers, while progeny with the same genotype and the dfr transgene produced red or purple tubers. HPLC and LC-MS/MS analyses of anthocyanins present in Chieftain and in a red-skinned progeny clone with the dfr transgene in a D-rrrr background revealed no qualitative diVerences. Thus, dfr can fully complement R, both in terms of tuber color and anthocyanin composition.

Increased accumulation of anthocyanins in transgenic potato tubers by overexpressing the 3GT gene

“…In the study of Zhang et al, the dihydroflavonol 4-reductase gene (dfr) was introduced into the potato cultivar Prince Hairy (white tuber) under the control of a double CaMV 35S promoter, resulting in a change in the color of the flowers of the transgenic plant from light blue to purple, but no change in tuber color (Zhang et al 2009). As shown in our results, under the mediation of the GBSSI promoter, only the color of the tubers deepened.…”

Linkage Mapping and QTL Analysis of Agronomic Traits in Tetraploid Potato (Solanum tuberosum subsp. tuberosum)

“…It is likely that the QTL we have detected is indeed the R locus. This hypothesis could be easily confi rmed because the gene for R, a dihydrofl avonol 4-reductase, has recently been cloned (Zhang et al, 2009). A QTL for pigmented fl owers was also located on chromosome II of B1829-5, but at a diff erent position (58 vs. 8 cM).…”

Root and Tuber Crops

“…Where genetic and biochemical information is available on metabolic pathways, such as those for carbohydrates, anthocyanins, and carotenoids in potatoes, candidate genes are being postulated and sought for improving both qualitative and quantitative traits. For example, Zhang et al (2009) have confirmed that the potato R locus codes for dihydroflavonol 4-reductase and that a specific allele of the dfr gene is required for the production of red pelargonidin-based anthocyanin pigments. Furthermore, advances in metabolite profiling are allowing a systems approach to understanding biochemical pathways and hence the key genes to target for desired phenotypic (trait) changes.…”