By Natasha Longo
Tomatoes were one of the first commercially available genetically modified (GM) crops ever. GM tomatoes are about to make a comeback in 2018 as Chinese and French researchers reveal details of how they genetically-engineered tomatoes to boost vitamins and other nutrients.
Earlier forms of this GM crop included the transgenic tomato (FlavrSavr) which had a “deactivated” gene. This meant that the tomato plant was no longer able to produce polygalacturonase, an enzyme involved in fruit softening. The premise was that tomatoes could be left to ripen on the vine and still have a long shelf life, thus allowing them to develop their full flavour. Normally, tomatoes are picked well before they are ripe and are then ripened artificially.
These GM tomatoes, however, did not meet their expectations. Although they were approved in the US and several other countries, tomatoes with delayed ripening have disappeared from the market after peaking in 1998.
Despite organic tomatoes being more nutritious than conventional, scientists think they can rise above nature to produce high nutrient GM tomatoes which produce compounds which are impossible in those naturally grown.
Tomatoes have recently been genetically modified to produce a peptide that mimics the actions of HDL cholesterol that biotechnology groups are promoting to supposedly reduce heart disease.
Producing A Genetically Modified Tomato
In collaboration with researchers from the University of Hong Kong (HKU), the team succeeded in isolating a specific plant chemical pathway to enhance phytosterol content by 94%, squalene (210%), provitamin A (169%) and lycopene (111%).
Currently there are no genetically modified tomatoes available commercially. In 2014, Norfolk Plant Sciences attempted to commercialise its produce, a genetically modified purple-fleshed tomato that contained high levels of anti-oxidants and anthocyanins.
Teaming up with Canadian-based New Energy Farms, the venture sought to grow a crop of blue tomatoes for use in clinical trials required to obtain regulatory approval.
In March of this year, Sainsbury Laboratory in Norwich, UK detailed a gene-editing technique (CRISPR/Cas9) that made tomatoes resistant to a potent fungal pathogen.
Led by Chye, the Wilson and Amelia Wong professor in plant biotechnology at HKU, alongside colleagues from the Institut de Biologie Moleculaire des Plantes in Strasbourg, France, the trial involved inserting a gene from an Indian mustard plant into a tomato plant.
The team found that as well as the boost vitamin E, provitamin A and lycopene compared to the control group, the increase resulted in a darker colour of the carotenoids extracted from the modified tomatoes.
GM Tomatoes in the EU
While tomatoes have been regularly used as a model organism to study the effect of climate in fruit ripening, its commercial history is a chequered one.
The Flavr Savr breed of tomato became the first commercially available genetically modified food engineered to have a longer shelf life. Launched in 1994, the tomato did not appeal to consumers and were withdrawn in 1997.
Currently Europe has yet to come to a decision regarding certain technologies implemented to create GMO foods.
In 2007, the European Union set up working groups to clarify how newer cis- and intragenic techniques fit into its existing prohibition of most genetically modified foods.
These working groups published a report in 2012, but not all recommendations were made available to the public.
The commission were scheduled to provide an update in 2015 but pushed back the release of its findings.
In 2016, the French Council of State asked the European Court of Justice (ECJ) to rule whether or not new GMO techniques, including CRISPR-Cas fell under EU GMO law.
The council also asked the ECJ if these ‘new plant breeding techniques’ were to become exempt from EU GMO rules, would this endanger the precautionary principle.
So far, no crops derived from these breeding techniques have yet received EU authorisation because of the uncertain legal situation.
One of the issues EU regulation is wrestling with is whether CRISPR is a definitive GMO technique.
There is the suggestion that CRISPR, when used to change a number of nucleotides to knockin or knockout various endogenous gene pathways in a crop organism, the plant is not considered GMO.
Conversely, an organism is considered GMO if CRISPR is used to insert an entire exogenous gene sequence into an organism.
According to the French Council of State, the ruling is expected around April 2018.