Agrobacterium-mediated gene transfer predominantly results in the integration of foreign genes at a single locus in the host plant, without associated vector backbone, and is also known to produce marker-free plants, which are the prerequisites for the commercialization of transgenic crops.

1. Agrobacterium
Mediated T-DNA
Transfer
1

2. HISTORY
1907: Smith and Townsend demonstrated that
Agrobacterium tumefaciens causes crown gall tumors.
Crown gall tumor on an oak tree
1958: Arnim Braun (Rockfeller Univ) showed that
tumors could be excised and propagated on in vitro
culture media without addition of plant hormones. It
was also demonstrated that tumor could propagate
even when the bacteria was removed from the
tumor. He proposed that the bacteria is able to
transfer “Tumor Inducing Principle” (TIP) into plant
cells
2

3. 1968: Georges Morel (France) found that the tumors released compounds
(opines) that Agrobacteria use as nutrients. Therefore, he proposed that:
(1) Bacteria transfer opine synthesis genes into plant cell, and
(2) The synthesized opine is transported back into the bacterial cell.
Transfer of genetic
material between
bacterial cells by
direct cell-to-cell
contact or by a bridge-
like connection
between two cells
1971: Hamilton and Fall (University of Pennsylvania) reported that a virulent
strain of Agrobacterium, when grown at 37oC lost virulence irreversibly.
Allen Kerr (Adelaide, Australia) co-inoculated “avirulent” and “virulent”
strains on sunflower, and re-isolated the “avirulent” strain. He found that
the “avirulent” strain had become virulent.
These results indicate that the TIP in Agrobactrium probably resides on a
plasmid, which can be transferred between bacterial strains by conjugation.
1974: Ivo Zaenan isolated the megaplasmids of Agrobacterium. He called
them Ti plasmids, which was later proven to be the TIP.
3

4. Features of Ti Plasmid
• About 200 kb.
• Opine catabolism region.
• T-DNA segment (transferred into plant cell).
• T-DNA carries gene for phytohormones (Cytokine
and Auxin) and opines that are expressed in plant
cell.
• Vir region for T-DNA transfer (virA, virB, virC,
virD, virE, virF, virH, and virG).
• virD have five genes (virD1-virD2) and virB have
eleven genes (virB1-virB11).
4

5. 5

6. 6

7. Recognition and attachment
Vir Genes Expression by
host signals
T-strand produce
T-complex export into host
Transport through
cytoplasm and Nuclear
T-DNA uncoating and
integration
7

8. 8

9. 9
Reference
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From crown gall tumors to genetic transformation. Physiological and Molecular Plant Pathology. 2011 Aug
1;76(2):76-81.
• Tzfira T, Citovsky V. Agrobacterium-mediated genetic transformation of plants: biology and biotechnology.
Current opinion in biotechnology. 2006 Apr 1;17(2):147-54.
• Deblaere R, Bytebier B, De Greve H, Deboeck F, Schell J, Van Montagu M, Leemans J. Efficient octopine Ti
plasmid-derived vectors for Agrobacterium-mediated gene transfer to plants. Nucleic acids research. 1985 Jul
11;13(13):4777-88.
• Zambryski P. Basic processes underlying Agrobacterium-mediated DNA transfer to plant cells. Annual review of
genetics. 1988 Dec;22(1):1-30.
• Wu H, Sparks C, Amoah B, Jones HD. Factors influencing successful Agrobacterium-mediated genetic
transformation of wheat. Plant cell reports. 2003 Mar;21(7):659-68.