Imagine yourself about to slice a fresh and perfectly red tomato only to find it watery and the taste to be so bland – you’re not alone. In fact, it is acceptable for you to not like the taste of the current commercially-produced red tomatoes because they’re meant to taste that way. However, it wasn’t always this way – back in the mid 20th century, our great grandparents may just enjoyed a better-tasting version of tomatoes compared to us. The reason why that changed is because of our obsession on aesthetically-pleasing, perfectly red tomatoes. Compared to today, tomatoes back then used to have greenish colour around the stem. While they taste sweet, fruit sellers realised that consumers tend to not choose these sort of tomatoes, but instead, opt for the perfectly red tomatoes. Due to this, farmers began to selectively grow tomatoes with this trait, a process known as artificial selection.
Unfortunately, little did farmers know, the gene responsible for controlling the uniform red colour of the tomato – which was conveniently named the ‘uniform’ gene, affected the sweetness of the fruit. The gene gives the fruit its red colour by disabling a protein called Golden 2-like protein 2 (GLK2). GLK2 is a transcription factor – molecules that regulates the expression of other genes. Some of those genes regulated by GLK2 is involved in the formation of chlorophyll, a structure that gives the organelle its green colour and absorbs sunlight for photosynthesis (plant’s way of producing sugar). Sugars produced from photosynthesis are accumulated and stored in the plant for energy reserve. Therefore, inhibited expression of these genes unsurprisingly resulted in the less sweeter taste of today’s red tomatoes. Other genes affected by GLK2 are involved in producing the pigment Carotenoids. Carotenoids make ripe tomatoes red and contributes to flavour as well.
To prove this connection, a study was published in 2012 confirmed the connection between GLK2 and the taste of tomatoes. They inserted sections DNA genomes of tomato plants that turned their GLK2s back on. The fruits of these genetically modified plants turned dark green before ripening because they contained 3 to 6 times more chlorophylls compared to regular tomatoes. Furthermore, after ripening, they contained 21% more sugar and 10 to 60% more Carotenoid lycopene.
Because of this, there has been a surge in popularity for the Heirloom tomatoes – wild varieties which haven’t had their GLK2 genes silenced. So, what seems delicious on the outside, may not be that tasty on the inside. Looks can be deceiving when it comes to tomatoes.
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Review Date: May 3, 2019 | Last Modified: November 27, 2019