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The Big Purple Tomato

By Josephine Pepper
The Big Purple Tomato

Under new US legislation, a “Big Purple Tomato” is one step closer to the supermarket shelves.  Will it seed enthusiasm for genetically engineered food around the world?

Scientists at Norfolk Plant Sciences have created a strikingly purple tomato by introducing genes which enhance production of anthocyanins, the molecules which give blueberries their colour and reported health benefits.  All tomato plants already contain anthocyanin-producing genes, but usually these genes are switched off in the tomato fruit itself.  To turn the tomato purple, two ‘on-switch’ genes were introduced from other plants, activating the tomato fruit’s anthocyanin production. Previous efforts to produce purple tomatoes (yes, there have been multiple attempts, through genetic modification as well as conventional breeding) have only managed to switch on these genes in a tomato’s skin, not in the flesh.  When these genes are expressed in tomato flesh, anthocyanins are produced in far higher levels, marking the tomatoes as indigo-coloured, nutritional ‘superfoods’.

The purple tomato is the first plant to complete the US Department of Agriculture’s new Regulatory Status Review process for genetically engineered crops (the SECURE rule, see here for more details).  The new process considers the biological consequences of an engineered plant’s genetic change and grants exemption from regulation if the engineered plants are not plausibly linked to an increased risk of pest or disease susceptibility.  It aims to streamline the regulatory process, making it easier and cheaper for smaller innovators to enter and disrupt the field.

Existing “biotech” crops grown in the US and elsewhere are overwhelmingly arable staples such as maize, soybean and cotton modified to carry traits like pest resistance and herbicide tolerance.  These have been developed by a roll-call of agricultural heavy-weights with the resources to take the crops through the older, more complex regulatory review procedures.  The modifications facilitate intensive, high-yield production, so the crops have traditionally appealed to farmers and distributors.  However, the new SECURE rule may also allow start-ups and SMEs to develop genetically engineered products focused more on consumer appeal, like the Big Purple Tomato.

The timing of the rule change could prove key.  Consumers have traditionally been wary of genetically engineered foods, particularly in Europe, despite data showing their safety.  But attitudes to diet are shifting fast, as we become more conscious of the environmental consequences of what we choose to eat and buy.  Plant-based diets, locally-sourced foods and sustainable agriculture are entering the spotlight, and willingness to alter dietary habits is at an all-time high.  Genetic engineering (introducing genes from other plant species, or extra copies of the plant’s own genes) and other genetic techniques such as gene editing (which adjusts DNA through more subtle alterations) represent powerful tools for reducing our food’s environmental footprint.  Already, plants have been modified to use less water, withstand changing climatic pressure, possess altered nutritional profiles for specialty uses or to accommodate changing diets, even to capture more carbon.  The Big Purple Tomato itself has a longer shelf-life, with obvious environmental implications for food waste.

Innovation in the space is booming; might purple tomatoes and other striking new plant varieties whet wary consumers’ appetites and allow us to reap the benefits of genetically altered crops?


Image Credit: Norfolk Plant Sciences