The 1907 "Blue Rose" exhibition of emergent Russian modern art was named for an impossible surreal image that existed only in the human mind. Conventional plant breeders attempted to make that dream a reality, but with purple results. In 1986, the Japanese whiskey distiller Suntory founded a Melbourne, Australia molecular engineering firm purposed toward achieving a commercial truly blue rose. That subsidiary, Florigene, produced roses bearing truly blue pigments in 2004.
Florigene began as Calgene Pacific Pty. Ltd. in Melbourne and changed name upon acquisition of Holland's Florigene B.V. in 1994. Florigene of Holland had identified the petunia "blue gene" in 1991. In 1995, the blue gene was introduced to the cultivar Florigene Moondust, a light mauve color carnation. In 1998, Florigene launched a deep violet carnation, first into the Australian market and later into the USA, Europe and Japan. Both of these flowers were shades of purple, because the gene to produce red pigments was not "turned off" when the blue pigment gene was introduced.
CSIRO Gene Silencing
The first step to create blue roses was to silence the dihydroflavonol reductase (DFR) gene that creates red pigments (anthrocyanins). In 1995, the Australian government's CSIRO (Commonwealth Scientific and Industrial Research Organisation) developed "gene silencing" using double-stranded RNA interference (hairpin RNAi). The folded strand of RNA attaches to an intron, a section of inactive DNA that does not code to a protein. The strand codes an opposing image of a coding section that physically blocks that section from coding. Florigene used CSIRO's tool.
Pansy and Iris
Rose anthocyanin pigments of red and orange accumulate in the fluid filled spaces of cell vacuoles. The combined pigments are influenced by vacuole pH and petal shape to create the flower color and markings that attract pollinators. When the genes that produce red anthocyanins were turned off, the genes that produce blue pigments could be turned on. Florigene cloned genes from a pansy to begin the production of the blue pigment delphinidin in roses and replaced the rose DFR gene with a blue pigment DRF gene from an iris.
Individual plant species rarely have blooms ranging the full spectrum of colors, because each plant specializes a limited range of anthocyanins. For example, petunias' DFRs lack a chemical substrate (dihydrokaempferol) necessary to make red and orange athocyanins. Iris blooms have a DFR similar to petunias. When a new biosynthetic pathway was engineered for roses, some genes were over-expressed and other genes were down-regulated. The pigment delphinidin was selected for blue roses, because the over expression of only one enzyme (F3'5'H) was necessary to produce delphinidin.
Not Coming to Your Local Nursery Soon
Blue roses will not be growing in your garden soon. Development costs prompted Suntory to target the luxury cut-flower market as they rolled-out the "Applause" blue rose cultivar in Japan only, beginning November 2009. Their projected price point equals 33 US dollars per flower. Prior to market, the Japanese government approved the bioengineered rose under existing international agreements on biosafety.