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Transgenic plants and their newly created traits

Using genetic engineering, scientists can tailor and modify various genomes to produce organisms with qualities that are beneficial for humans. Transgenic animals are useful in medical research. Diseased phenotype in the “dish” allows scientists to track the pathology, reveal unknown facts and test potential drugs…Transgenic plants are modified for other purposes: to provide better harvest, to increase amount of valuable nutrients, to strengthen the plants against herbicides, to delay ripening. Unlike transgenic animals, transgenic plants could be (and they usually are) part of our everyday meals.

Most common modifications on plants

Plants release protective chemicals when exposed to the stressful environmental conditions such as very high or low temperature, drought, and increased salinity of the soil... These chemicals include sugars like trehalose and fructans, sugar alcohols like mannitol, amino acids like proline, glycine, betaine and proteins such as antifreeze proteins. Scientists created plants that overexpress genes responsible for stress-releasing chemicals, resulting in better adapted and stronger plants that could survive in the harsh environmental conditions. Glycine betaine is a cellular osmolyte produced via combined activity of choline dehydrogenase, choline monooxygenase and few other enzymes. When choline oxidase gene (derived from Arthrobacter sp.) was introduced into rice genome, transgenic rice developed resistance to drought due to increased level of glycine betaine.

Tolerance against herbicide

Herbicides are inevitable part in plant cultivation because weed grows wherever crop is growing (and competes for water and nutrient with crop). Since herbicides are very aggressive chemicals, crops need to be modified to remain safe. Herbicides target enzymes that are essential for the survival of the plant. Without selected enzyme, biological pathway can’t be completed and lack of vital nutrient eventually lead to plant death. Several approaches are applied while designing transgenic plants resistant to the herbicide. Plant will remain safe if it becomes genetically modified to produce excessive amount of target protein or if target protein underwent genetic modification. Detoxifying system of the plant could be enhanced by boosting natural systems for detoxification or by incorporating foreign genes that could help in toxin elimination. All these methods proved to be effective. Glyphosate is widely used herbicide because it kills 76 out of 78 problematic weed species. He is competitive inhibitor (competes with pyruvate) of 5-enoyl-pyruvylshikimate 3-phosphate synthase (EPSPS) enzyme. It was noted that petunia has several copies of EPSPS gene. Insertion of petunia's EPSPS genes into crop’s DNA increased resistance against herbicides 2-4 times. EPSPS gene can be altered by simple switch of cytosine with thymine, which results in modified final protein that can’t combine with glycophosphate. Introduction of foreign gene that encodes glycophosphate oxidase (derived from Ochrobactrum anthropi) increases transformation of glyphosate into glyoxylate and aminomethylphosponic acid and accelerates detoxification.

Tolerance against insecticides

Insects, mites and nematode can damage the harvest greatly. That means that either synthetic insecticides or genetic engineering methods must be applied to ensure safe and rich harvest. Transgenic plants are more eco-friendly compared to synthetic insecticides and so far, 40 gene candidates of various microorganisms that live on higher plants and animals were detected as useful in increasing plant’s tolerance against insecticides. The most popular and often used are Bt-genes isolated from the bacterium Bacillus thuringiensis. List of transgenic plants containing Bt-toxin increased since 1996 (when first Bt-plant became commercially available) and they include: corn, soybeans, cotton, rice, maize, potato, and tomato….Authorities claim that Bt-toxin is not harmful to the humans because it undergoes metabolic degradation after ingestion. Latest studies proved them wrong. According to the results from the Sherbrooke University Hospital in Quebec, Bt-toxin was found in 93% of pregnant women, in 80% of tested umbilical cord blood and in 67% of non-pregnant women. Bt-toxin is associated with cancer development, autism, food allergies and auto-immune diseases and number of diagnosed cases is increasing constantly for the past couple of years. People exposed to the Bt-toxin spray (another way to repel insects is to cover plant's surface with Bt-toxin via spray) showed symptoms like flu and allergy. Same symptoms were recorded in people in India who were in direct contact with genetically altered Bt-cotton. Although creators of the Bt-toxin claim that Bt-food is safe, it turned out that toxin can be found in the body several years after last transgenic meal is consumed.

Last example of genetically modified food is not the only experiment that shows how dangerous transgenic plants can be. While waiting for the final conclusion on transgenic plants safety, you can always choose not to eat them.