Agrobacterium tumefaciens is a soil bacterium that can integrate its own DNA into the DNA of plant cells.
T-DNA is the section of Agrobacterium DNA that is transferred into plant cells. Within Agrobacterium, T-DNA is part of a small circular DNA sequence called the Ti plasmid.
To infect a plant, Agrobacterium attaches to a root and makes a transport channel between its own cytoplasm and that of a root cell. A single-stranded piece of T-DNA is released from the Ti plasmid.
The T-DNA passes through the transport channel along with some Agrobacterium proteins.
The T-DNA moves through the plant-cell cytoplasm and into the nucleus.
Finally, the T-DNA is integrated into the plant’s own DNA. The genes on the T-DNA can now be expressed in the plant cell.
Researchers often use Agrobacterium to make transgenic plants in the lab. They replace the Agrobacterium genes on T-DNA with the gene they are studying, and the Agrobacterium integrates the new gene into the plant cell’s DNA.
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