BOTANY Higher Secondary Second Year - Textbooks Online

4.2 Transgenic plants
Introduction of foreign gene
In genetically engineered plant cells, a bacterium Agrobacterium is
mainly involved in transfer of foreign gene. However, Agrobacterium
cannot infect all plants since it has a narrow range of host specificity.
Therefore other techniques have been developed to introduce foreign DNA
into plant cells. Novel methods of ensuring DNA uptake into cells include
electroporation and mechanical delivery or biolistics.
Electroporation is a process of creating temporary pores in the cell
membrane by application of electric field. Creation of such pores in a
membrane allows introduction of foreign molecules such as DNA, RNA,
antibodies, drugs, etc. into cytoplasm. The development of this technique
is due to contribution of biophysics, bioengineering, cell and molecular
biology. While the technique is now used widely to create transgenic
microorganisms, plants and animals, it is used increasingly for application
of gene therapy.
The mechanical particle delivery or gene gun methods to deliver
DNA on microscopic particles into target tissue or cells. The process is
increasingly used to introduce new genes into a range of bacterial, fungal
plant and mammalian species. It is the main method of choice for genetic
engineering of many plant species including rice, corn, wheat, cotton and
soyabean.
Transgenic (modified) plants
Presently, more than 50 types of genetically engineered plant species,
called transgenic plants have been successfully developed. These plants
were made to resist insect pests, viruses or herbicides through incorporation
of foreign gene into DNA of host plant cells. Initially transgenic plants
were developed more in dicotyledons, but now extended to several
monocotyledons like wheat, maize, rice and oats. Transgenic plants have
also been developed and are suitable for food industries (delaying ripening
in tomato).
Gene pharming, the use of transgenic plants as bioreactors or factories
for production of speciality chemicals and pharmaceuticals is being pursued
151