The rose family, represented by the genus Rosa, has long been a favorite of gardeners and breeders, offering a stunning array of colors. Despite centuries of cultivation, blue remained notably absent from the natural palette. This absence sparked a long horticultural quest for a truly blue rose, often symbolizing the unattainable. Roses naturally lack the genetic machinery required to synthesize blue pigment, a biological barrier that traditional breeding could not overcome. The solution required a shift to modern genetic engineering.
The Specific Name of the Engineered Rose
The genetically engineered flower is commercially marketed as Suntory Blue Rose ‘Applause’. The Japanese company Suntory collaborated with the Australian company Florigene to create this variety. The ‘Applause’ rose was first announced in 2004 and became commercially available in 2009, representing a major biotechnology achievement. Despite the name, the actual color is not a true blue, but rather a shade of lilac, pale mauve, or lavender. The challenge of achieving a pure, deep blue remains due to biochemical factors like the rose petal’s natural acidity. However, the introduced blue pigment gives it a distinctly blue-violet tone compared to traditional lavender roses.
The Biological Barrier to Natural Blue Color
Blue roses do not exist in nature because of the specific pigments roses produce. Flower color is determined by a class of compounds called anthocyanins, which are synthesized through a complex metabolic pathway. Roses naturally produce red and yellow pigments, specifically cyanidin and pelargonidin, resulting in the familiar red, pink, orange, and yellow spectrum.
Roses are unable to produce delphinidin, the anthocyanin responsible for blue and violet colors. This inability stems from the lack of a specific enzyme in the rose genome. The missing component is flavonoid 3′,5′-hydroxylase, or F3’5’H. Without the F3’5’H enzyme, the biochemical pathway cannot add the necessary hydroxyl groups to the flavonoid structure to create delphinidin.
How Genetic Engineering Created the Color
Researchers overcame this natural barrier by introducing the missing F3’5’H enzyme into the rose genome using genetic engineering. They isolated the F3’5’H gene from the wild pansy (Viola tricolor), a plant that naturally produces blue flowers. This foreign gene was then cloned and prepared for insertion into the rose’s DNA.
The gene transfer process, known as transgenesis, was accomplished using the soil bacterium Agrobacterium tumefaciens. This bacterium has a natural ability to insert its own DNA into a plant’s genome, which scientists repurpose as a tool to deliver the desired foreign gene. The engineered bacterium delivered the pansy’s F3’5’H gene into the rose cells, enabling them to synthesize delphinidin.
To enhance the blue color, scientists also used RNA interference (RNAi) technology. This suppressed the rose’s own dihydroflavonol 4-reductase (DFR) gene, which typically directs the production of red pigments. By suppressing the competing red pigment and adding the blue pigment gene, researchers shifted the flower’s color to the desired blue-violet hue.