Genetically modified (GM) plants are created by inserting DNA from another organism into their genome. Here's a breakdown of the process:
Key Steps in Creating GM Plants
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Identifying and Isolating the Desired Gene: The process begins with identifying a gene that confers a desirable trait (e.g., pest resistance, herbicide tolerance, increased nutritional content) from another organism, be it a bacterium, virus, or even another plant. This gene is then isolated and copied.
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Gene Insertion into a Vector: The isolated gene is then inserted into a vector. A vector is a carrier molecule that delivers the new DNA to the plant cell. The most common vector is Agrobacterium tumefaciens, a bacterium that naturally infects plants and inserts its DNA into their genome. Plasmids (small circular DNA molecules) derived from this bacterium are often used. Alternatively, gene guns can be utilized, which physically shoot DNA-coated particles into plant cells.
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Transformation: This is the process of introducing the vector containing the desired gene into plant cells. There are several methods:
- Agrobacterium-mediated transformation: Plant tissue (e.g., leaf discs) is exposed to Agrobacterium containing the desired gene. The bacterium infects the plant cells and transfers the gene into the plant's DNA.
- Gene gun (biolistics): Tiny gold or tungsten particles are coated with the DNA and then "shot" into plant cells using a device called a gene gun. Some of the DNA integrates into the plant's genome.
- Protoplast transformation: Plant cell walls are removed, creating protoplasts. These protoplasts can then take up DNA directly through electroporation (using electrical pulses to create pores in the cell membrane) or other chemical treatments.
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Tissue Culture and Regeneration: After transformation, the plant cells are grown in tissue culture. This is a sterile environment where cells are provided with nutrients and hormones that stimulate cell division and differentiation. The cells that have successfully incorporated the new gene are selected and allowed to develop into whole plants.
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Selection and Screening: Not all plant cells will successfully integrate the new gene. Therefore, a selection process is used to identify the transformed cells. This often involves using a marker gene alongside the desired gene. For example, a gene that confers resistance to a particular herbicide can be used as a marker. Only cells that have integrated the herbicide resistance gene (and hopefully the desired gene) will survive when exposed to the herbicide. The plants are then screened to confirm the presence and expression of the desired gene.
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Plant Breeding and Seed Production: The resulting GM plant is then grown to maturity, and its seeds are collected. These seeds will inherit the new DNA, ensuring that future generations of the plant also possess the desired trait. The GM plant may also be crossed with other varieties to introduce the new trait into existing cultivars.
In summary, creating genetically modified plants involves transferring specific DNA sequences into plant cells, selecting for successful transformants, and regenerating those cells into whole plants that stably inherit the new trait.
