The introduction of T-DNA into plants involves :

The introduction of T-DNA into plants involves :
  1. Altering the pH of the soil, then heat-shocking the plants
  2. Exposing the plants to cold for a brief period
  3. Allowing the plant roots to stand in water
  4. Infection of the plant by Agrobacterium tumefaciens

Solution

Ti plasmid of Agrobacterium tumefaciens: Agrobacterium  tumefaciens, a pathogen of several dicot plants is able to deliver a piece of DNA known as ‘T-DNA’ to transform normal plant cells into a tumor and direct these tumor cells to produce the chemicals required by the pathogen. This bacterium invades plants at the site of wound, transforming them and nearby cells to form a tumor called crown gall.

When the bacterium contacts a damaged plant cell, it delivers a T-DNA (transferred DNA) fragment from plasmid into host cell that integrates at a random position in plant cells chromosome. The tumor inducing (Ti) plasmid of A. tumefaciens has now been modified into a cloning vector which is no more pathogenic to the plants but is still able to use the mechanism to deliver genes of interest.

Asked in: NEET 2015 (Phase 2)

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