Re: my Question is regarding Genetically Modified Food

Hi Fatima,

Regular mango trees require a frost free environment to produce fruit, although the trees can withstand a few degrees below freezing temperatures for a short time. To modify them so that they can withstand a Canadian winter, and still produce fruit would be a lot more complex than simply giving them a gene for cold tolerance.

Plants that do live in places with very cold winter not only have to withstand the cold temperature, but also coordinate their growth and development with the changing seasons. For example, plants become dormant during the winter, basically shutting down metabolic processes at least in the above ground portion of the plant) for the duration of the cold weather. This is an essential part of surviving the winter. When spring comes, they break dormancy and grow again. To ensure that the occasional warm day in February doesn’t trick them into thinking its spring, plants can essentially keep track of how long it’s been cold, and won’t break dormancy until the weather has been cold for a certain number of days. This actually creates a problem for fruit growers in warmer climates: some varieties of apple, for example, will not break dormancy after a mild winter. So if you try to grow a northern climate apple in the south, the tree will not “wake up” in the spring, because it’s still waiting for winter to finish.

Modifying a mango tree with a gene for cold tolerance may allow it to survive a few degrees colder for short periods of time, but it won’t allow it to survive an extended cold winter. It’s unlikely that a tropical plant like a mango tree has the ability to become dormant, and it’s also unlikely that it has the ability to keep track of how long it has been cold. Both of these abilities are controlled by complex genetic programs that are not completely understood, so it is not possible at this time to confer transfer that ability to a mango tree by genetic modification.

Simpler and more realistic targets for plant genetic modification include disease resistance and nutritional improvement. There are several antifungal genes known that could be used to make a plant resistant to fungal diseases. Some viral diseases have been controlled by modifying plants to express altered forms of the viral assembly proteins. When the altered proteins are present in the plant cells, new viral particles do not assemble efficiently, slowing or halting the spread of the virus.

Since the biosynthetic enzymes (and the corresponding genes) for many vitamins are known, it is possible to genetically modify plants to produce increased quantities of particular vitamins. The only example I know of this is the production of beta carotene in rice (our bodies convert beta carotene into vitamin A), but others should be possible.

The enzymes that synthesize different plant pigments are also known, and these could be used to create flowers of different colors than usual, a blue rose for example.

Alex Brands