True blue flowers are a rarity in nature—they occur only in
select species like morning glories and delphiniums. Now,
researchers have created a genuinely blue chrysanthemum by adding
two genes to the normally pink or reddish flower. The advance could
be applied to other species—and it may mean that florists wanting
to hawk blooms of blue will no longer have to dye them.
“This [advance] is of great impact,” says Toru Nakayama, a plant
biochemist at Tohoku University in Sendai, Japan, who was not
involved with the work. There are several popular commercial
species for which no true blue varieties exist, he notes.
We all think we’ve seen blue flowers before. And in some cases,
it’s true. But according to the Royal Horticultural Society’s color
scale—the gold standard for flowers—most “blues” are really violet
or purple. Florists and gardeners are forever on the lookout for
new colors and varieties of plants, however, but making popular
ornamental and cut flowers, like roses, vibrant blue has proved
quite difficult. “We’ve all been trying to do this for a long time
and it’s never worked perfectly,” says Thomas Colquhoun, a plant
biotechnologist at the University of Florida in Gainesville who was
not involved with the work.
True blue requires complex chemistry. Anthocyanins—pigment
molecules in the petals, stem, and fruit—consist of rings that
cause a flower to turn red, purple, or blue, depending on what
sugars or other groups of atoms are attached. Conditions inside the
plant cell also matter. So just transplanting an anthocyanin from a
blue flower like a delphinium didn’t really work.
Naonobu Noda, a plant biologist at the National Agriculture and
Food Research Organization in Tsukuba, Japan, tackled this problem
by first putting a gene from a bluish flower called the Canterbury
bell into a chrysanthemum. The gene’s protein modified the
chrysanthemum’s anthocyanin to make the bloom appear purple instead
of reddish. To get closer to blue, Noda and his colleagues then
added a second gene, this one from the blue-flowering butterfly
pea. This gene’s protein adds a sugar molecule to the anthocyanin.
The scientists thought they would need to add a third gene,
“That allowed them to get the best blue they could obtain,” says
Neil Anderson, a horticultural scientist at the University of
Minnesota in St. Paul who was not involved with the work.
Chemical analyses showed that the blue color came about in just
two steps because the chrysanthemums already had a colorless
component that interacted with the modified anthocyanin to create
the blue color. “It was a stroke of luck,” Colquhoun says. Until
now, researchers had thought it would take many more genes to make
a flower blue, Nakayama adds.
The next step for Noda and his colleagues is to make blue
chrysanthemums that can’t reproduce and spread into the
environment, making it possible to commercialize the transgenic
flower. But that approach could spell trouble in some parts of the
world. “As long as GMO [genetically modified organism] continues to
be a problem in Europe, blue [flowers] face a difficult economic
future,” predicts Ronald Koes, a plant molecular biologist at the
University of Amsterdam who was not involved with the work. But
others think this new blue flower will prevail. “It’s certainly an
advance for the retail florist,” Anderson says. “It would have a
lot of market value worldwide.”
As for Noda and other scientists, the blue blooms mean that at
long last, they understand the biochemistry of this remarkable
color.