(2)Genetic Engineering of Plants

Agrobacterium tumefaciens

A Gram-negative soil bacterium that naturally transforms dicotyledonous plants. It transfers a portion of its Ti (tumor-inducing) plasmid into the plant cell's genome.

Ti Plasmid

A large plasmid in A. tumefaciens that contains genes essential for the transformation process.

vir Genes

Genes on the Ti plasmid essential for T-DNA transfer and integration into the plant genome. They are induced by plant phenolic compounds.

T-DNA

The region of the Ti plasmid that is transferred to the plant cell's genome. It contains genes for plant hormone biosynthesis (auxin, cytokinin) and opine synthesis.

Auxin

A plant hormone that, when overproduced due to T-DNA genes (iaaM, iaaH), causes cell proliferation and tumor formation.

Cytokinin

Another plant hormone, overproduction of which (due to tmr/ipt gene) contributes to tumor formation in infected plants.

Opine

Unique condensation products of amino acids and keto acids or sugars, synthesized by enzymes encoded by T-DNA genes. They serve as a carbon and nitrogen source for Agrobacterium.

Binary Vector

A shuttle vector active in both E. coli and A. tumefaciens. A. tumefaciens contains a disarmed Ti plasmid with vir genes but lacking functional T-DNA.

Disarmed Ti Plasmid

A modified Ti plasmid that has had its tumor-producing genes removed, making it safe for creating transgenic plants. It retains the necessary components for T-DNA transfer and integration.

Cointegrate Vector

Contains plant selectable marker gene, target gene, RB, E. coli ori, and bacterial selectable marker gene. Disarmed Ti plasmid lacks tumor-producing genes and RB of T-DNA.

A physical method of gene transfer where DNA-