1. Agrobacterium tumefaciens
Characteristics
Plant parasite that causes Crown Gall Disease
Encodes a large (~250kbp) plasmid called Tumor-inducing (Ti) plasmid
Portion of the Ti plasmid is transferred between bacterial cells and plant cells  T-DNA (Tumor DNA)

2. Agrobacterium tumefaciens
T-DNA integrates stably into plant genome
Single stranded T-DNA fragment is converted to dsDNA fragment by plant cell
Then integrated into plant genome
2 x 23bp direct repeats play an important role in the excision and integration process

3. Agrobacterium tumefaciens
Tumor formation = hyperplasia
Hormone imbalance
Caused by A. tumefaciens
Lives in intercellular spaces of the plant
Plasmid contains genes responsible for the disease
Part of plasmid is inserted into plant DNA
Wound = entry point  days later, tumor forms

4. Agrobacterium tumefaciens
What is naturally encoded in T-DNA?
Enzymes for auxin and cytokinin synthesis
Causing hormone imbalance  tumor formation/undifferentiated callus
Mutants in enzymes have been characterized
Opine synthesis genes (e.g. octopine or nopaline)
Carbon and nitrogen source for A. tumefaciens growth
Insertion genes
Virulence (vir) genes
Allow excision and integration into plant genome

5. Ti plasmid of A. tumefaciens

7. Auxin, cytokinin, opine synthetic genes transferred to plant
Plant makes all 3 compounds
Auxins and cytokines cause gall formation
Opines provide unique carbon/nitrogen source only A. tumefaciens can use!