Transgenic Plants: Methods, Applications, and Examples
Understanding Transgenic Plants: Creation & Impact
A transgenic plant is a modified organism where genes are transferred from one organism to another through genetic engineering techniques. The primary purpose of producing a transgenic plant is to obtain a species that possesses ideal traits, high yield, and enhanced quality.
Methods for Gene Transfer in Plants
Two primary methods are used to transfer genes into plants:
Agrobacterium-Mediated Gene Transfer
Agrobacterium tumefaciens is a plant pathogen known to cause crown gall disease, characterized by swellings (galls) on plants, typically at or just above the soil line. Upon infecting plants, it transfers a segment of its genetic material (T-DNA) to the host, which eventually becomes incorporated into the plant genome.
For genetic engineering purposes, the bacterium is engineered with a tumor-inducing (Ti) plasmid containing desirable genes and then used to infect the plant. The Ti plasmid is a circular plasmid that naturally transfers its T-DNA to the plant host chromosomes and is responsible for causing the galls.
Particle Bombardment / Gene Gun Method
As the name suggests, in this method, the desired gene is coated onto microscopic gold or tungsten particles and then propelled into plant cells. Once inside, the gene sequence can integrate into the plant’s genome, and these modified cells can then be regenerated into whole plants using tissue culture methods.
Applications of Transgenic Plants
Enhanced Resistance to Biotic and Abiotic Stress
Biotic stress results from the actions of living organisms such as viruses, bacteria, pests, and pathogens. To mitigate such stress, plants are engineered with disease-resistant genes, leading to improved crop yield and quality.
Abiotic stress, caused by environmental factors, can severely damage plants. Soil composition, humidity, water availability, and temperature are crucial factors for plant growth. Climate change can alter these factors. Thus, plants are engineered with stress-tolerant genes for enhanced resilience and production.
Increased Nutritional Value (Biofortification)
Biofortification is the process of increasing the nutritional value of a crop. Malnutrition is a common problem in developing countries. As a solution, plants are engineered to produce crops of better nutritional value.
Production of Recombinant Proteins
While recombinant human proteins have been produced using animal and microorganism systems, the plant system offers advantages due to certain shortcomings of other methods. Vaccines and therapeutic proteins have been obtained from transgenic plants. However, this application is still largely in the developmental stage and has not yet been widely commercialized.
Examples of Transgenic Plants
Golden Rice
Developed to combat Vitamin A deficiency, particularly in children. Using gene gun methods, rice varieties were engineered with phytoene synthase genes, significantly increasing their Vitamin A content.
Bt Cotton
A genetically modified cotton variety resistant to the bollworm pest.
Flavr Savr
A genetically modified tomato with delayed ripening and softening, resulting in an extended shelf life.