Among the various vectors used in plant transformation, the Tiplasmid of Agrobacterium tumefaciens has been used extensively. This bacterium contains large-sized plasmid, known as Ti-plasmid (tumour-inducing plasmid) and a portion of this plasmid referred to as T-DNA (transferred DNA).
When is transferred to plant genome, in the infected cells it causes these plant tumours (crown galls). This means that A. tumefacient has natural ability to transfer T-DNA of its plasmid into the plant genome (plant chromosomes) upon infection of cells at the wounded site and therefore this bacterium is known as ‘natural genetic engineer of plants’. Ti-plasmid can be used as a vector for inserting useful foreign genes into a genome of plant cells.
