This page was created by undergraduate students as a course assignment for a GMO seminar.
Reducing Undesirable Components
Permission pending from BBC online news
Today, tea and coffee are staple beverages in most people's diets. For reasons of personal preference, or for health reasons, many people drink decaffeinated coffee. The current method of decaffeinating coffee involves using a chemical solvent to remove the caffeine from the coffee beans (along with much of coffee's flavor) and then replacing much of the liquid that contains the coffee's flavor. The solvent of choice is methylene chloride, which has been questioned as a possible carcinogen. In addition, chemically decaffeinated coffee is said to taste worse than regular coffee. Also, the decaffeination of tea (which undergoes a similar process as decaf coffee) removes many antioxidants and flavonoids that are beneficial to the human body. All of these factors make coffee and tea prime candidates for genetic modification (Is decaf tea healthy?).
A group of scientists in Japan have engineered a coffee plant that produces low levels of caffeine naturally. By interfering with the enzyme theobromine synthase, the scientists have succeeded in producing a coffee plant that is 70% lower in caffeine levels. The enzyme is responsible for the synthesis of theobromine, a precursor to caffeine. Without the precursor, the plant cannot produce caffeine (Ogita, 2003). Another possible method of reducing caffeine expression in plants is to overexpress a gene that produces a protein responsible for demethylating caffeine. By demethylating caffeine, it is reduced to an intermediate which is easily broken down without the side effects of caffeine (Ashihara, 2001).
Many plants that are consumed produce allergen proteins, which can cause various adverse reactions. These can range from asthma-like allergies to anaphylaxis (Buchanan, 1997). In order to curtail these problems, scientists are beginning to inhibit the production of the proteins responsible for these reactions. Buchanan et al. have isolated the protein responsible for allergies in wheat. Elimination of this protein should lead to reduced allergenicity in wheat (Buchanan, 1997). Rabjohn et al. have found that by introducing a missense mutation into the Ara h 3 gene reduces the ability of the resulting protein to interact with the immune system. Because the immune system would not be stimulated, the food allergy would hypothetically disappear (Rabjohn, 2002).
In addition to removing allergens and other potentially harmful compounds such as caffeine, other compounds that affect the way a food looks can also be removed. For example, when potatoes are damaged, they release an enzyme called polyphenol oxidase, which causes the plant to develop brown and black bruises. These bruises are not detrimental to nutritional value, nor do they affect the taste, but they are unappealing to consumers. CSIRO has engineered a potato that inhibits this enzyme. By not producing the enzyme, the potatoes are much less likely to bruise. Other than the absence of polyphenol oxidase, the potatoes had a normal phenotype (CSIRO, 2003).
Created by Ashley Cain, Will Greendyke, and Leigh Anne Hoskins
Last updated 4/14/04
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