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Agrobacterium; the natural ‘genetic engineer’

Agrobacterium tumefaciens is a Gram negative soil bacteria, which has natural genetic engineering capability by which it integrates its plasmid genes into plant genome. This is a natural process and we are exploiting bacteria’s ability to transfer our gene of interest into the plants.
Why bacterium enter into such association?
Agrobacterium tumefaciens will transfer genes(T-DNA region of Ti plasmid) into the plant that produces its food or nutrient called opines (opines are not needed for plants). Apart from that, it also integrates genes for cell division and proliferation leading to crown gall disease. So that more number of cells result in more production of opines.

Crown gall disease caused by Agrobacterium tumefaciens
About Agrobacterium?
Agrobacterium is a Gram negative, rod shaped soil bacterium that belongs to the family Rhizhobeaceae.
Major species include:
  • Agrobacterium tumefaciens: that causes ‘crown gall disease’ in wounded dicot plants.
  • Agrobacterium rhizhogenes: that induces hairy root disease in plants.
  • Agrobacterium radiobacter: an avirulent strain.
Reason for crown gall and hairy root disease?
Smith and Townsend (1907) found out Agrobacterium tumefaciens as the causative agent of crown gall disease. Agrobacterium tumefaciens has a 200kb plasmid called as Ti plasmid (tumor inducing plasmid) which is responsible for crown gall disease.
Agrobacterium rhizhogenes has a plasmid called as Ri plasmid( root hair inducing plasmid) which is responsible for hairy root disease.

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