State how has Agrobacterium tumifaciens been made a useful cloning vector to transfer DNA to plant cells.
Agrobacterium tumifaciens transfers a piece of DNA called 'T-DNA' in the host cell which transform normal plant cells into a tumor and direct these tumor cells to produce the chemicals required by the pathogen. The tumor inducing (Ti) plasmid of Agrobacterium tumifaciens has been modified into a cloning vector. The gene coding for T-DNA is cut with the help of restriction endonuclease. The gene of interest can be jointed with the help of ligase enzyme to make a cloning vector. Plasmid then can be used to deliver genes of our interest into a variety of plants.