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Toying with genes

Last updated: 16 August, 2010

GENETICS

By inserting two genes from daffodils and one gene from a bacterial species into rice plants, Swiss researchers have produced rice capable of synthesising beta-carotene. Genetic engineering has brought about many such marvels, from disease-free crops to edible vaccines. Marvels from a science perspective, but ethical issues abound, writes B R Guruprasad

Man has been known to make life easier for himself over centuries, from domestication of animals to raising crops for food. Today, scientists can directly toy with genes to alter plants and animals for food. The result of this process is a genetically modified organism (GMO).

Notwithstanding the moral dilemmas that come with GMOs, scientifically speaking, it has opened up a new world. Biotechnology has allowed farmers to raise crops that are resistant to strains of bacteria or insecticides.

Thanks to selective breeding of plants which involves choosing certain seeds that have greater resistance to disease and pests than others, farmers have been able to raise more crops. But, with the introduction of genetic engineering, modifications to plants and animals no longer have to be done through the selective breeding process.

What’s a transgenic crop plant?

A transgenic crop plant contains a gene or genes which have been artificially inserted instead of the plant acquiring them through pollination. The inserted gene sequence (known as the transgene) may come from another unrelated plant, or from a completely different species. Transgenic Bt cotton, for example, produces its own insecticide and contains a gene from a bacteria. Plants containing transgenes are often called genetically modified or GM crops.

Future transgenic products

Tomatoes are one of the world’s most popular vegetables. Lycopene, a naturally occurring constituent of tomato, is a nutritional factor related to Vitamin A. Transgenic tomato with enhanced lycopene content is under investigation.

Another trait of interest is delayed ripening. Tomatoes that ripen slower can remain on the vine longer and develop improved flavour, compared to commercial varieties picked at the green colour stage.
Millions suffer from Vitamin A deficiency, which leads to vision impairment, increased susceptibility to diarrhoea, respiratory diseases and measles etc.

Rice is a staple food in many countries, particularly in Asia, but does not contain Vitamin A or its immediate precursors. By inserting two genes from daffodils and one gene from a bacterial species into rice plants, Swiss researchers have produced rice capable of synthesising beta-carotene, the precursor of Vitamin A.

This rice variety is now being crossed into adapted varieties, with field tests possible in a year or two. Canola is a major oilseed crop. Research has focused on improving the nutritional quality of canola oil by enhancing the Vitamin E content or by modifying the balance of fatty acids.

Edible vaccines?

Food crops engineered to produce edible vaccines against infectious diseases would make vaccination more readily available to children around the world. Because of their palatability and adaptation to tropical and subtropical environments, bananas have received considerable research attention as a vehicle for vaccine delivery. Transgenic bananas containing inactivated viruses that cause cholera, hepatitis B and diarrhoea have been produced and are currently undergoing evaluation.

Two scientists in Hawaii and Scotland have identified different genes that lead to the production of caffeine in coffee beans and tea leaves. If these genes can be removed in some plants, coffee and tea trees could be developed that would produce naturally decaffeinated products with full flavour and aroma. Grape vines are susceptible to several diseases that reduce the amount and the quality of wine grapes and table grapes or even those that kill it.

Researchers at the University of Florida have patented a method for producing grape vines that carry a silkworm gene to provide protection from disease that affects grapes and other plants. Nicotine-free tobacco is now being grown for a projected introduction of nicotine-free cigarettes. Previous attempts to make low-nicotine products removed some of the flavour along with the nicotine. Genetically engineered nicotine-free tobacco doesn’t synthesise nicotine in the leaf. This product is from Pennsylvania.

Soil salinity

Soil salinity is a key problem on the agriculture front. Increase in salinity is because of a decrease in the water table, poor drainage and topical irrigation. Is there a possibility of using the genes of salt tolerant plants species in our agricultural crops?

Mangroves are one such plant species, which may be able to provide several options to decrease the amount of salinity within the soil. Mangroves have the unique ability to bring in salt water through their roots, remove it from the water, and release the salts through their leaves where the wind carries it away. It may be possible to remove some of the salts in the soil by growing mangroves in areas of high salt content or by isolating the genes that allow them to grow in areas of high salt concentration and placing them in our traditional field crops.

Plants are being classically bred for salt tolerance but nothing has been successful. An alternative to this could be for scientists to genetically modify plants to be salt tolerant. Mangroves contain genes allowing it to tolerate and live in saline conditions. A gene from the grey mangrove, Avicennia marina, has been genetically implanted into a tobacco plant.

Plants surviving the gene transfer show an increase in the ability of the tobacco plant to tolerate salt stress as well as showing tolerance to other ionic stresses. It may be possible to use the gene found in the grey mangrove as well as find other mangrove genes allowing it to tolerate salt and transfer them to food crops. However, there are many ethical issues related to the growing and consumption of genetically engineered crops because of safety and environmental concerns.

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