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The below mentioned article highlights the five main features of transgenic plants which include:
(1) Contain Transgenes (2) Involve Biotechnology (3) Bypass Sexual Process (4) Low Frequency and (5) Utility.
Feature # 1. Contain Transgenes:
Transgenic plants contain transgenes (foreign genes). The foreign genes maybe utilized from unrelated plants, microbes and animals. Microbial genes are utilized from fungi, bacteria and viruses. Sometimes, genes from DNA synthesized in the laboratory are also used for development of transgenic plants.
Feature # 2. Involve Biotechnology:
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Development of transgenic plants involves plant biotechnology, which refers to the combination of tissue culture and genetic engineering. In other words, transgenic plants are developed through tissue culture and genetic engineering.
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The genetic engineering helps in manipulation of foreign gene (DNA) and tissue culture is essential for genetic transformation. The foreign gene cannot be inserted into whole plant. It can only be inserted into single cells. Thus, tissue culture is essential for transfer of foreign gene into single cells.
The genetic transformation can be achieved either through cell culture or protoplast culture. Moreover, tissue culture is essential for regeneration of genetically transformed single cells into whole plant. Thus combination of tissue culture and molecular genetics is essential for development of transgenic plants.
Feature # 3. Bypass Sexual Process:
In the development of transgenic plants, the sexual process (reproduction) is bypassed. In other words, transgenic plants are developed without involving sexual fusion between donor and the recipient parents. As stated above, transgenic plants are developed by the techniques of tissue culture and genetic engineering. Once a transgenic plant is developed, the transgenic trait can be transferred to other genotypes through backcross method.
Feature # 4. Low Frequency:
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In most of the field crops, transgenic plants are recovered at a very low frequency Hence, huge single cells or protoplasts have to be screened in the culture medium for identification and isolation of transgenic cells. The transformed cells are identified by polymerase clain reaction (PCR) technique.
When a transgene is introduced into the genome of an organism, it can achieve one of the following:
(i) Produce a protein of interest:
It produces a protein that is the product in which we are interested. The protein hirudin present in leech prevents blood clotting. Its gene was chemically synthesized and introduced in Brassica napus. The seeds of the latter came to have hirudin which could be extracted and purified.
(ii) Produce a desired phenotype:
It produces a protein that on its own produces the desired phenotype. The best known example of this is the use of cry genes in corn and other crops. Bacillus thuringiensis, is a naturally occurring soil bacterium that produces a crystal (Cry) protein that is toxic to insect larvae. Crystal protein genes have been transferred into corn, enabling the corn to produce its own pesticides against insects such as the European corn borer.
(iii) Modify an existing biosynthetic pathway:
It modifies an existing biosynthetic pathway so that a new end product is obtained. Transgenic Rice and transgenic Potato produce respectively higher content of vitamin A and protein.
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(iv) Mask expression of a native gene:
It prevents the expression of an existing native gene. In ‘Flavr Savr’ variety of tomato, expression of gene for production of polygalacturonase was blocked. Enzyme polygalacturonase degrades pectin. In the absence of enzyme, pectin degradation is stopped and the fruit remains fresh for long. It retains flavour, has superior taste and higher quantity of total soluble solids.
Feature # 5. Utility:
Transgenic plants are developed to solve specific problems in crop plants such as development of plants having resistance to diseases, insects, drought, frost, salinity and metal toxicity; improvement in keeping quality of some vegetables, and fruits; and development of male sterility, etc.
