(b) Explain in detail about various types of direct gene transfer method.

Explanation

a. Chemical mediated gene transfer: Certain chemicals like polyethylene glycol (PEG) and dextran sulphate induce DNA uptake into plant protoplasts.
b. Microinjection : The DNA is directly injected into the nucleus using find tipped galls needle or micro pipette to transform plant cells. The protoplasts are immobilised on a solid support (agarose on a microscopic slide ) or held with a holding pipette under suction.
c. Electroporaton Methods of Gene Transfer . Apulse of high voltage is applied to protoplasts, cells or tissues which maker transient pores membrane through which uptake of foreign DNA occurs
d. Liposome mediated method of Gene Transfer : Liposome the artificial phospholipid vesicles are useful in gene transfer . The gene of DNA is transferred from liposome into vacuole of plant cells. It is carried out by encapsulated DNA into the vacuole . This technique is advantageous because the liposome protects the introduced DNA from being damaged by the acidic pH and protease enzyme present in the vacuole . Liposome and tonoplast of vacuole fusion resulted in gene transfer. This process is called lipofection .
e. Biolistics : The foreign DNA is coated onto the surface of minute gold or tungsten particles (1-3 `mu`) and bombarded onto the target tissue or cells using a particle gum ( also called as gene gun/micro projectile gun/shotgun). Then the bombarded cells or tissue are cultured on selected medium to regenerate plants from the transformed cells.