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Genetic Engineering of Plants: Aims strategies for development of transgenic  

Meaning of Genetic Engineering:

• Recombinant DNA Technology (rDNA Tech) or genetic engineering is concerned with the manipulation of genetic materials towards desired end in a directed way. 
• It is also known as gene cloning. 
• Plant genetic engineering is defined as the isolation, introduction and expression of foreign DNA in the plant. In other words, it refers to direct introduction or foreign gene (DNA) into a plant’s system by micromanipulation at the cellular level.
• By the conventional plant breeding techniques, significant achievements have been made in the improvement of several food crops.
• These age- old classical methods, involving gene transfer through sexual and vegetative propagation, take very long time.
• For instance, about 6-8 years may be required to develop a new rice or a wheat by sexual propagation. 
• Rapid advances in gene structure and function, coupled’ with the recent developments made in the genetic engineering techniques have dramatically improved the plant breeding methods to yield the desired results in a short period.
• Plant genetic transformation technology basically deals with the transfer of desirable gene(s) from one plant species to another (or insertion of totally new genes) with subsequent integration and expression of the foreign gene(s) in the host genome. 
• The term transgene is used to represent the transferred gene, and the genetic transformation in plants is broadly referred to as plant trans-genesis.
• The genetically transformed new plants are regarded as transgenic plants. 
• The development of transgenic plants is the outcome of an integrated application of recombinant DNA (rDNA) technology, gene transfer-methods and tissue culture techniques.

Why Transgenic Plants?

• It is only through the recombinant approach (genetic engineering) of biotechnology, new genes with desired characters (that may or may not be present in other plants) can be introduced into the plants. 
• Further, it is possible to manipulate the existing genes to make the proteins with suitable alterations e.g. increase in the content of an essential amino acid.
• The most important reasons for developing transgenic plants are listed:

1. To improve agricultural, horticultural or ornamental value of plants.
2. To develop plant bioreactors for inexpensive manufacture of commercially important products e.g. proteins, medicines, pharmaceutical compounds.
3. To study the action of genes in plants during development and various biological processes.

Genetic Traits Introduced into Transgenic Plants:

• Since plant cells are totipotent (i.e. a single plant cell can regenerate into a whole plant), the genetically engineered cells with new gene(s) can produce a transgenic plant. 
• This plant carrying the desired trait will give raise to successive generations.
• Many genetic traits have been introduced into plants through genetic engineering:

1. Resistance to herbicides
2. Protection against viral infections
3. Insecticidal activity
4. Improved nutritional quality
5. Altered flower pigmentation
6. Tolerance to environmental stresses
7. Self-incompatibility

Criteria for Commercial Use of Genetically Transformed Plants:

• For large-scale commercial application of genetically engineered plants, the following requirements have to be satisfied:

1. Introduction of desirable gene(s) to all plant cells.
2. Expression of cloned genes in the appropriate cells at the right time.
3. Stable maintenance of new gene(s) inserted.
4. Transmission of new genetic information to subsequent generations.