Not all potential applications of genetic modification of plants concern food plants, however. In this section, we will describe two other potential applications of genetically modified plants: phytoremediation and human vaccine production in plants.
Phytoremediation is the act of cleaning up polluted soils with plants. As we know, vast stretches of land, worldwide, are heavily polluted with petrochemicals or toxic heavy-metal salts such as mercury and cadmium. It so happens that soil microbes are often able to detoxify these pollutants by degrading petrochemicals and immobilizing heavy metals. However, there are potential problems with spraying contaminated soils with these microbes, for fear of creating yet another environmental problem. This is where GM plants may come to the rescue. Why not isolate the relevant bacterial genes and transfer them to plants? Plants do not move, can grow fast, and, through their roots, absorb polluted water, thereby concentrating toxic chemicals inside their cells. When engineered with bacterial genes, these GM plants would be able to survive. After their detoxification job was achieved, they could be harvested and burned under controlled conditions. And yes, this has been done. There now exist fast-growing GM poplar trees able to detoxify petrochemicals and salts of various heavy metals. Their positive effects have been tested on a small scale, and research is being pursued for other pollutants using poplar trees as well as other plants.
Finally, plants, one day, may be a source of readily accessible human vaccine. Vaccines are made from disabled pathogens, such as viruses or bacteria, so that they can no longer cause disease but instead provoke an immune reaction and thus provide protection from the pathogen. When people are injected with a part of a pathogen called an antigen, their immune system produces specific antibodies that block the antigen. Vaccinated people, when exposed to the pathogen, will also block it, thanks to their newly acquired antibodies. Vaccination works very well to avert a host of viral and microbial diseases. Vaccines, though, typically require refrigeration and must be injected using sterile syringes. These are not always easy to come by in developing countries: hence the idea of producing vaccines in edible plants. This concept has been successfully demonstrated: a gene from the Newcastle virus (a pathogen that causes severe diarrhea) has been cloned and expressed in potatoes. Volunteers who ate these GM potatoes developed antibodies against the virus. These GM potatoes had to be eaten raw, because boiling or frying would have destroyed the antigen. Since most people would not enjoy chewing on raw potatoes, the banana is now being considered for genetic modification with antigen genes. Vaccination campaigns with GM plants have not yet started, however. Amusingly, since vaccines are pharmaceuticals, the idea of producing them in plants has been dubbed "pharming." Clearly, other proteins of medical importance could potentially be produced in GM plants. One great advantage is that plants cannot be contaminated with human viruses, while plant viruses are harmless to humans.
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Detoxification is something that is very important to the body, but it is something that isn't understood well. Centuries ago, health masters in the East understood the importance of balancing and detoxifying the body. It's something that Western medicine is only beginning to understand.