It was discovered that tumor formation results from the transfer of bacterial genes into the plant genome. The region transferred is called T-DNA and is a segment of a plasmid, the Ti plasmid. In addition, an antibiotic resistance gene was added within the T-DNA region to allow for the selection of transformants. The Agrobacteria transfer T-DNA into the plant cells. The plant tissue is then allowed to grow on selective media.
Transgenic plantlets regenerate which are readily grown to mature plants.
Agrobacterium -mediated transformation of Arabidopsis is even easier. Plants that are just beginning to flower are dipped into a solution of Agrobacterium . Flowers are allowed to mature and seeds are harvested. All seeds germminate, untransformed plants turn yellow while transformed plants remain healthy and green. Other methods are available for transforming plants.