The successful development of the transgenic plants has made it possible to produce some of the most costly recombinant proteins and industrial enzymes at much lower costs and at much larger scale. In order to develop the transgenic plants, it is very important to transfer the gene of interest into the plant cells and successfully express it. In the following paragraphs we’ll look at the various techniques employed to transfer the gene of interest into the plants.
Vector-mediated or indirect gene transfer
In this method the gene of interest is transferred using a vector which is usually a disarmed pathogen which contains the necessary tools required to transfer the gene in the plant cells.
The most widely used vector for gene transfer is Agrobacterium tumefaciens. This is a bacterium which is responsible for causing the crown gall disease in the plants. In order to use it for transferring the gene of interest, the Ti plasmid of the bacterium is modified by cloning the gene of interest in the T-DNA region and removing the sequence responsible for pathogenicity. Upon successful modification of the plasmid, it is introduced in the bacterium and upon infection on the plant; it inserts the gene of interest into the plant genome.
In addition to the vector mediated gene transfer method, there are various vector-less methods of gene transfer which are also termed as direct gene transfer methods.
Chemical mediated gene transfer
Chemicals like polyethylene glycol (PEG) induce the plant protoplasts to uptake the foreign DNA and incorporate it into its genome. Calcium phosphate is also used to introduce the DNA into the cultured cells.
This technique is used to introduce the DNA in the large sized cells such as oocytes and the early embryonic cells. The DNA is introduced inside the cell using fine tipped (0.5-1.0 micrometre diameter) needle.