Gene behind pink tomatoes identified

Washington: Sweet, pink-skinned tomatoes are said to be one of the favourites of Far Eastern diners. Now, researchers from Weizmann Institute``s Plant Sciences Department have identified a gene, which gives these tomatoes its unique colour.

Lead researcher Asaph Aharoni reveals that mutations in a gene called SIMYB12 is behind the pink colour.

During the study, researchers focused 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. 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 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 Aharoni.

"This ability could accelerate efforts to develop new, exotic tomato varieties, a process that can generally take over 10 years," Aharoni added.