The beloved tomato is the one fruit many still think is a vegetable. Few also realize that tomatoes were one of the first commercially available genetically modified (GM) crops ever. Under the guise of incorporating healthier and concentrated natural compounds, GM tomatoes are about to make a comeback on new research that aims to pack in the same amount of resveratrol as 50 bottles of red wine into one tomato.
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 areÂ 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.
Same Potency As 50 Bottles of Red Wine
Researchers say their GM tomatoes could provide the same amount of resveratrol as 50 bottles of red wine or the same amount of genistein as 2.5kg of tofu, say researchers.
“We are not sure why there is so much emphasis on genistein,” said author and GMO researcher Rebecca Israel. “We know that too much genistein is detrimental to a developing child, so why would we want to increase this phytoestrogen in something as common as a tomato,” she stated.
The findings, published in Nature Communications, claim to suggest a way to produce industrial quantities of potentially beneficial natural compounds efficiently — by growing them in genetically modified tomatoes.
Led by Dr Yang Zhang and Dr Eugenio Butelli at the John Innes Centre in the UK, the research team tested the effect of introducing a protein called AtMYB12 — which activates a set of genes involved in the production of producing natural compounds — and genes encoding enzymes specific for making resveratrol and in to tomatoes.
According to the team, the protein acts a bit like a tap to increase or reduce the production of natural compounds depending on how much of the protein is present.
Zhang and Butelli revealed that the genetic modifications acted to both increase the capacity of the plant to produce natural compounds (by activating phenylpropanoid production) and to influence the amount of energy and carbon the plant dedicated to producing these natural compounds.
Indeed, introduction of the AtMYB12 protein meant tomato plants began to create more beneficial compounds including resveratrol and genistein, and devoted more of energy to doing this, but what is the consequence. “We simply don’t know what consequences will result from the introduction and amplification of gene sequences,” said Israel.
The team noted that because tomatoes are a high yielding crop — producing up to 500 tonnes per hectare in countries delivering the highest yields — and require relatively few inputs, the production of valuable compounds like resveratrol or genistein in tomatoes could be economical compared to relying on artificial synthesis in a lab.
There are many other biotech projects aiming to enrich tomatoes with substances that may offer health benefits which claim to be more nutritious, however no human or long-term studies are planned to discover their effects on metabolism.
Monsanto developed tomatoes that delayed ripening by preventing the production of ethylene, a hormone that triggers ripening of fruit. Although the tomatoes were briefly tested in the marketplace, patent arguments forced its withdrawal.
Tomatoes (along with potatoes, bananas and other plants) are also being investigated as vehicles for delivering edible vaccines. Clinical trials have been conducted on mice using tomatoes that stimulate antibody production targeted to norovirus, hepatitis B, rabies, HIV and anthrax.
Korean scientists are looking at using the tomato to expressing a vaccine against Alzheimer’s disease. Hilary Koprowski, who was involved in the development of the polio vaccine, is leading a group of researchers in developing a tomato expressing a recombinant vaccine to SARS.
Although GM foods can only be planted in many countries as part of a trial, and even then only under strict conditions, millions of hectares of the crops have already been planted in the Americas.
Campaigners have warned that there is no compulsory labelling of meat or dairy products from animals which have been fed on GM crops, and that any long-term problems from eating the foods is still unknown.
About the Author
Natasha Longo has a master’s degree in nutrition and is a certified fitness and nutritional counselor. She has consulted on public health policy and procurement in Canada, Australia, Spain, Ireland, England and Germany.
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