Introduction:
Transgenesis is the process of introducing a foreign gene (transgene) into an organism’s genome to produce new traits.
Plants that carry this foreign gene are called transgenic plants. These plants can exhibit improved traits such as pest resistance, higher yield, or better nutritional value.
1. What is Transgenesis?
Transgenesis involves transferring a specific gene from one organism (donor) to another (recipient) using genetic engineering techniques.
The introduced gene can come from a different species, allowing the recipient plant to show new characteristics that don’t naturally exist in it.
2. Steps in Creating Transgenic Plants:
Identification of Desired Gene:
Select a gene that carries the desired trait (e.g., drought resistance).
Gene Isolation:
Extract the desired gene from the donor organism.
Gene Insertion (Transformation):
Insert the gene into the plant’s DNA using methods like:
Agrobacterium tumefaciens (bacteria used as a vector).
Gene Gun (bombards plant cells with DNA-coated particles).
Regeneration of Plants:
Grow the transformed cells in tissue culture to produce whole plants.
Screening and Selection:
Identify and select the plants that successfully express the transgene.
Field Testing:
Test the transgenic plants under field conditions to ensure they perform as expected.
3. Examples of Transgenic Plants:
Bt Cotton:
Contains a gene from the bacterium Bacillus thuringiensis that produces a protein toxic to specific insects.
Provides resistance to bollworms, reducing pesticide use.
Golden Rice:
Engineered to produce vitamin A to combat malnutrition.
Contains genes from daffodils and bacteria.
Herbicide-Tolerant Soybeans:
Tolerant to glyphosate, allowing easier weed control.
Virus-Resistant Papaya:
Resistant to papaya ringspot virus (PRSV), saving the papaya industry in some regions.
4. Applications of Transgenic Plants:
Pest Resistance:
Pest are a threat to the crops grown in the fields usually these pest are controlled by pesticides, which have more disadvantages like
These pesticides are accumulated in the soil and polluting them.
They can be accumulated by the plant itself which threatens the plants and the products which are obtained from the crops and become unsuitable for consumption.
To minimise the use of pesticides, biopesticides can be used which do not accumulate in the soil and are less toxic to the plants and humans, which are generally obtained from microorganisms. Many microorganisms like bacillus, Shigella, can be used as a biopesticides among which bacillus thuringiensis is mostly used.
It is known to have it in which is known as the “Cry Gene”. Which can undergo transcription and translation producing protein called δ endotoxins, which is a large molecular weight toxic protein.
When bacillus thuringiensis used as a biopesticide, the toxin produced by the bacterium will be consumed by the insect within the midgut of the insect and the δ endotoxin is broken down into a small molecular weight active endotoxin in the presence of an enzyme protease with alkaline pH. The production of these active endotoxin leads to paralysis and finally death of the insect.
Through transgenic technology the crygene from Bacillus Thuringiensis can be isolated and injected into the crop plant itself. So, within the crop plant the cry gene gets expressed producing the endotoxin, which can efficiently control the pest.
This technique is mostly used for cotton plants. Example: Bt Cotton.
Disease Resistance:
Production of transgenic plants which are resistant to several pathogens like bacterium, fungal or viral pathogens. Example, the plant which is prone to fungal infection, making it resistant to those pathogens using transgenic technology.
Most plants have the capacity to produce PR Proteins, which are pathogenesis related proteins. These PR protein provide 🫴 resistance against fungal infection, which can be used to make our crop plant resistance towards fungal infection.
The gene responsible for production if PR Protein (PR Gene) is isolated and inserted into the crop plants, where within the crop plants PR Genes get expressed producing the PR Protein.
These PR Proteins show chitinase and glucanase activity, which can degrade the cell wall of the fungal pathogen, hence making it inactive and protecting the crops from fungal pathogens.
What is PR Protein and how do they work? 🤯
Improved Nutritional Quality:
Enhances the levels of vitamins or minerals.
Example: Golden rice enriched with vitamin A.
Herbicide Tolerance:
Herbicides are chemicals which are used to kill the herbs (small weeds), which are seen growing along with the crops. These weeds are known to acquire all the nutrients, water and the space, which is supplied to the crop plants. As a result, there is less chance for the crop plants to survive in the field along with the weeds. To avoid these, herbicides or weedicides are used to kill to weeds, but there are chances that the spraying of herbicides can affect the growth of crop plants ☘️ . Therefore it is necessary to make the crop plants resistant to the herbicides. For example, Glyphosate is used as a herbicide, which can inactivate one of the enzymes which is involved in the pathway of an important component in the plant.
As Glycophosate can inactivate one of these enzymes, the fatty acid pathway or amino acid pathway can be inhibited. Hence the weeds can be destroyed.
But there are chances that the crop plants can also be affected by these herbicides 🌿. Through transgenic technology it could be appropriate to make the crop plant resistant to Glyphosate.
It is known that the bacterium vibrio has EPSP Genes, which can produce the enzyme enol pyruvyl shikimate phosphate synthetase. Which is said to be resistant against Glyphosate.
The EPSP gene 🧬 from vibrio is isolated and inserted into the crop plant using agrobacterium mediated gene transfer (either binary vector or cointegrated vector) into the crop plant.
Within the crop plant the EPSP gene get expressed producing EPSP synthetase enzyme, which offer resistance against Glyphosate. Hence herbicide resistant transgenic plants are produced
Example: Glyphosate-resistant soybeans.
Stress Tolerance:
Transgenic plants resistant to abiotic stress.
Abiotic stress in plants includes high salinity, high temperature, drought condition etc. Through transgenic technology drought resistant plants can be produced. For example, most of the plants have two important enzymes.
Choline MonoOxygenase (CMO)
Betaine Aldehyde Dehydrogenase (BADH)
They are involved in the production of a compound called glycine betaine, which is known to offer resistance against high salt conditions and resistance against drought conditions.
CMO converts choline into glycine aldehyde, which again converts to glycine betaine with the help of BADH.
To make the crop plant resistant to high salt concentration and drought conditions, the genes for the production of CMO & BADH are isolated and inserted into crop plants. Within the crop plants the gene gets expressed producing CMO & BADH, Which is ultimately responsible for converting choline into glycine betaine making the plant resistant against high salinity and crop resistant.
5. Advantages of Transgenic Plants:
Higher Yield: Increases crop production.
Reduced Pesticide Use: Lowers environmental pollution.
Better Quality Crops: Enhanced nutrition and longer shelf life.
Disease and Pest Resistance: Protects against harmful pathogens and insects.
6. Disadvantages:
Environmental Risks: Potential impact on non-target organisms.
Cross-Pollination: Risk of genes spreading to wild relatives.
Ethical Concerns: Some people oppose genetic modifications.
Costly Technology: Developing and testing transgenic plants is expensive.
Conclusion:
Transgenesis allows scientists to create transgenic plants with specific traits that benefit agriculture.
These plants can help address global food security, reduce chemical use, and improve nutrition. However, their use requires careful management to address environmental and ethical concerns