Agrobacterium Mediated Transformation | Biotech Studies

AGROBACTERIUM MEDIATED TRANSFORMATION

Agrobacterium mediated transformation is vector mediated gene transfer method.

Agrobacterium :-

• It is gram negative bacteria belonging to two bacteria family of rhizobiaceae.
• Found in soil
• It cause diseases like crown gall disease hairy root disease etc

History :-

• Smith & Townsend (1907)- said bacteria caused crown gall disease.
• Brown & Stonier (1958)-proposed that not whole bacteria but some part of it causes disease.
• Zaenen et.al (1974)- noted virulent strain- Agrobacterium tumefaciens.
• Chilton et.al (1977)-reported Ti & Ri plasmid transfer to plant causing disease.

Classification of agrobacterium mediated transformation

• it is of two type

1. Based upon phytopathogenic characteristics :-

• Tumefaciens :- it causes crown gall disease.
• Rhizogenes :- it induces hair root disease.
• Radiobacter :- it is an avirulent strain.

2. Based upon growth pattern :-

• Biotype 1
• Biotype 2
• Biotype 3

Genetic map of an octopine Ti plasmid

Virulence genes :-

• Virulence region consists of 24 genes in total.
• Virulence genes are located in 8 operons from vir A-vir H.
• vir A vir F and vir G are monocistronic operons, where as vir B,C,D,E,H are polycistronic.
• vir A senses Acitosyringone.
• vir G transcriptional activator of vir box
• vir B conjugational pores between plant cell and bacteria.
• vir D, essential for cleavage of super coiled stranded substrate.
• Vir E responsible for gene transfer protein.
• Vir C helps in DNA transfer.
• vir B, ATPase activity- provides energy for DNA

Chromosomal genes :-

• Chv A& B major role in exopolysaccharide production.
• psc A major role in T-DNA transport.
• chv E glucose and galactose transport.
• chvD, ilv, miaA,and att, have virulence property.