How to Change the DNA of a Plant

The transformation of plants can be accomplished in several ways. Two of the most common methods in agricultural crops are the use of Agrobacterium tumefaciens, and biolistics (the “gene gun”).

Using the bacterium Agrobacterium tumefaciens provides a natural mechanism for transformation. The bacterium infects injured plant tissue and transfers its Ti plasmid to the plant’s chromosome. The Ti plasmid naturally contains genes that cause the plant tissues to overexpress plant hormones and nutrients for the bacteria, leading to plant tumors. The Ti plasmid may be modified to delete unwanted effects and add desirable traits, along with a selectable marker, which is then integrated into the plant’s chromosome during bacterial infection. However, not all species are susceptible to infection by this bacterium.

Over the course of the last decade, a second method of transformation has grown more popular than Agrobacterium: biolistics, also known as the “gene gun” method. In this method, plasmid DNA is coated onto small tungsten or gold beads. These micron-sized beads are then “shot” into the plant tissue. Some of the cells in the plant tissue may successfully take up the new DNA and integrate it into a chromosome. This method has proven effective for integrating DNA into the cell nucleus as well as into organelles such as chloroplasts, and works in almost all species researched. Other methods that have been used include microinjection and electroporation.