PCP Award: Engineering of the Rose Flavonoid Biosynthetic Pathway Successfully Generated Blue-Hued Flowers Accumulating Delphinidin

Abstract

Roses lack violet to blue flower varieties due to the absence of delphinidin-based anthocyanins, usually the major constituents of violet and blue flowers, because roses do not possess flavonoid 3',5'-hydoxylase (F3'5'H), a key enzyme for delphinidin biosynthesis. We selected hosts of genetic transformation that would be suitable for the exclusive accumulation of delphinidin and the color change toward blue. Expression of the viola F3'5'H gene in some of the selected cultivars resulted in the accumulation of a high percentage of delphinidin and a novel bluish flower color. Furthermore, we down-regulated the endogenous dihydroflavonol 4-reductase (DFR) gene and overexpressed the iris DFR gene in addition to the F3'5'H gene in a cultivar. The resultant roses exclusively accumulated delphinidin, and the flowers had blue hues not achieved by hybridization breeding. The ability for exclusive accumulation of delphinidin was inherited by the next generations.