Agrobacterium

Agrobacterium tumefacients are gram-negative phytopatogenic soil bacteria. These bacteria may carry short DNA sequences with its Ti plasmid into cells of another plant. In nature Agrobacterium naturally infects plants, inserting its genes directly into plant cells and causing tumours in plants. Genes, causing diseases in plants, are removed from the genetically modified agrobacteria. However, they still may infect plants, but without causing diseases. In order to transform plants, experimenters insert extraneous genes, which they wish to study, into agrobacteria, which in turn transfer the genetic information into plants during infection. Upon introduction of a transgene along with the marker gene necessary for selection into the T-part of the Ti plasmid and infection of a plant by such bacteria, these genes are integrated into the genome of the plant. When fragments of the plant are being grown on a medium containing antibiotics (kan, neo, etc.), modified cells form a callus, which non-modified cells die. A modified plant develops effectively from the callus.

Transformation by means of agrobacteria is the most widely used method for obtaining of transgenic plants.