January 18, 2010 – Dr.
Asaph Aharoni of Israel’s Weizmann Institute’s Plant Sciences Department has
revealed the gene that’s responsible for producing pink tomatoes.
January 18, 2010 – Dr.
Asaph Aharoni of Israel’s Weizmann Institute’s Plant Sciences Department has
revealed the gene that’s responsible for producing pink tomatoes.
Dr. Aharoni’s research
focuses on plants’ thin, protective outer layers, called cuticles, which are
mainly composed of fatty, wax-like substances. In the familiar red tomato, this
layer also contains large amounts of antioxidants called flavonoids that are
the tomatoes’ first line of defense.
Some of these flavonoids
also give the tomato cuticles a bright yellow cast – the colour component that
is missing in the translucent pink skins of the mutants.
Using a lab system that’s
unique in Israel, and one of only a few in the world, Aharoni and his team are
able to rapidly and efficiently identify hundreds of active plant substances
called metabolites. A multidisciplinary approach developed over the past
decade, known as metabolomics, enables them to create a comprehensive profile
of all these substances in mutant plants and compare it with that of normal
ones.
The research, carried out
in Dr. Aharoni’s lab by Dr. Avital Adato, Dr. Ilana Rogachev and research
student Tali Mendel, showed that the differences between pink and red tomatoes
go much deeper than skin colour. The scientists identified about 400 genes
whose activity levels are quite a bit higher or lower in the mutant tomatoes.
The largest changes, appearing in both the plant cuticle and the fruit
covering, were in the production of substances in the flavonoid family. The
pink tomato also has less lycopene, a red pigment known to be a strong
antioxidant that’s been shown to be associated with reduced risk of cancer,
heart disease and diabetes. In addition, alterations in the fatty composition
of the pink tomato’s outer layer caused its cuticle to be both thinner and less
flexible that a regular tomato’s skin.
The researchers found that
all of these changes can be traced to a mutation on a single gene known as
SIMYB12. This gene acts as a “master switch” that regulates the activities of a
whole network of other genes, controlling the amounts of yellow pigments as
well as a host of other substances in the tomato.
“Since identifying the
gene, we found we could use it as a marker to predict the future colour of the
fruit in the very early stages of development, even before the plant has
flowered,” said Dr. Aharoni. “This ability could accelerate efforts to develop
new, exotic tomato varieties, a process that can generally take over 10 years.”
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