There is a broad range of methods that are employed in the process of producing GMOs. This often involves insertion of a gene of interest into living organisms depending on the species that you are working on. In plants mainly, two most common biotechnology-based techniques include; Agrobacterium-mediated transformation and bombardment of particles. According to the regulations given by FSANZ, it is a requirement that clear description of the method employed in genetically engineering plants is given.
Case study- Roundup Ready soy
This was produced using the particle bombardment method. This process of biotechnologically engineering soybeans involved; bombardment of the plant cells with microscopic particles of gold coated with DNA that contains the gene of interest. The gene of interest is the EPSPS gene that is derived from Agrobacterium. The aim of this is to introduce the novel gene of interest through the cell wall so that it integrates into the genetic material of the soy plant.
The new round up soy that is genetically engineered contains a new gene that codes for the EPSPS enzyme. The new plant cell controls the activity of all the genes through the use of regulatory sequences. These regulatory sequences do not code for any protein but rather plays a central role in the regulation of gene activity in the soy plant by either switching the genes on or switching them off. However, in the case of the roundup soy, plant cells often do not recognize the regulatory genes derived from bacterial cells. This means that when the regulatory sequences are introduced from the bacterium into the plant, the regulatory DNA has to be replaced with those that can be recognized by the plant. Thus, the EPSPS gene derived from Agrobacterium works in the soy plant through replacement with those that are recognized by the soy plant.
The figure above demonstrates the manner in which gene regulation takes place in the roundup soy. At the front of the bacterial EPSPS gene in the roundup, soy is the regulatory sequence that directs the plant to switch genes on or off. This is the CaMV 35S promoter sequence is derived from cauliflower mosaic virus. At the end of the EPSPS gene is another regulatory gene that directs the gene of interest to end. This is referred to as NOS 3’’ and is derived from nopaline synthase gene in bacteria but can function in plants.
Another regulatory sequence that is introduced into the soy plant is the chloroplast transit peptide gene that is derived from a petunia. The role of this gene is to direct the soy plant cell to transport the bacterial EPSPS gene into the chloroplast of the plant cell. This is because for the soy plant to demonstrate tolerance to roundup herbicides, the EPSPS enzyme has to be present in the chloroplast. This is because this is the location where the amino acids that make up the protein are produced. Once the EPSPS enzyme is in the chloroplast, the chloroplast transit peptide is eliminated for the gene of interest to function.
With this GMO soy plant, standard molecular biotechnological methods were employed in demonstrating that a single complete copy of the bacterial EPSPS gene was present and flanked by two DNA sequences found in the genome of the roundup ready soy plant. This is an indication that the right size and correct sequence of the gene of interest were genetically engineered into the soy plant to confer resistance to herbicides.
Additionally, the novel gene introduced into the roundup ready soy was assessed in the third and the sixth generation of soy plants using biotechnological approaches. This indicated that the new gene of interest was stable and had integrated itself well into the Soy genome. Again, the roundup ready feature of the soy plant was examined across a wide range of generations thus indicating its ability to be passed on from the parents to the offspring in a rational and predictable manner following the laws of heredity.
The issues that arise from the discovery and production of the GM roundup ready soy are mostly relevant to the potential transfer of the gene that confers antibiotic resistance from the GM soy foods to the gut of the bacteria. However, it is important to note that roundup ready GM soy does not contain the antibiotic resistance gene, but the only gene that could potentially be transferred to the human digestive system is the bacterial EPSPS gene. This gene does not have any impact on the people’s health since EPSPS gene in the GM soy plant functions in a similar manner as the one predominantly found in the bacterial gut. There is also no evidence that points at the ability of the new gene in GM soy having a potential to integrate into the DNA genome of humans and thus poses no known health hazard. Additionally, there is no sequence similarity to the gene to allergens and thus has no ability to cause allergenic reactions.
The genetically engineered soy is similar in structure as well as function to the naturally occurring soy plants while the EPSPS gene in plants and bacteria are also similar regarding the roles they play. However, the difference between the two soy varieties is based on the fact that the GM soy is more tolerant to herbicides as compared to the other naturally occurring type. According to scientific publications of GM soy, there is a single amino acid alteration in the EPSPS enzyme that confers its tolerance to glyphosate. On the other hand, the bacterial EPSPS enzyme is made up of over 400 amino acids. Additionally, bacterial EPSPS levels present in fresh edible soy constitutes less than 0.1 % of the total protein levels. According to research, the enzyme of interest in the GM soy has not been demonstrated to have any activity when eaten. This is because the enzyme is inactivated upon exposure to heat during food processing.
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