The Pink Gene

Rosy-red tomatoes are a common ingredient in most people’s salad, but diners in the Far East are partial to a slightly different pink-skinned tomato, and scientists have just discovered a master gene responsible for the tomato’s unusual colour.

Dr Asaph Ahroni and his team at the Weizmann Institute’s Plant Sciences Department focused on the fatty, wax-like outer layer of the tomato – the cuticle – and used a unique lab system to rapidly and efficiently identify active plant substances called metabolites, creating a comprehensive profile of the plant. They compared metabolites in normal and mutant plants, and discovered that a single gene ¬– SIMYB12 – is responsible for regulating the activity of other genes, including colour.

The research showed that the differences between the two tomatoes went much deeper than skin colour. Aharoni and his team identified around 400 genes whose activity levels are elevated or lessened in mutant tomatoes compared to the ‘regular red’ tomato. The largest changes – appearing in the plant cuticle and fruit covering – were in the production of the flavonoid family. The pink tomato – which tastes sweeter – contained much less lycopene, a red pigment known to be a strong antioxidant. The fatty composition of the tomatoes outer layer caused its cuticle to be thinner and les flexible than that of a regular 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.”