Gene Transfer from Bacteria to Plants : Genetic Engineering in Nature

Agrobacterium tumefaciens, a common soil bacterium causes the destructive plant disease, crown gall, characterized by the formation of tumorus overgrowths at the site of infection. These overgrowths result from the transfer of DNA and proteins from Agrobacterium into plant cells where the DNA is integrated into the plant genome, and expressed, leading to the synthesis of plant growth regulators and food for the bacteria. This transfer of DNA from a prokaryote to a eukaryote is the only recognized natural example of trans-kingdom gene transfer. Indeed, most tobacco plants contain Agrobacterium genes that resulted from an infection in the distant past. Interestingly, the transfer mechanism used by Agrobacterium is common to the mechanism used by many human pathogens to transfer proteins into human cells, thereby causing disease. This natural genetic engineer has been exploited to genetically transform agriculturally important plants to confer resistance to a wide range of harmful pests, such as insects and viruses, as well as to herbicides. Agrobacterium can transfer DNA into many other eukaryotes including algae, fungi and human cells in the laboratory. Other bacteria, besides Agrobacterium are now being developed to genetically engineer plants and other organisms. What many biologists once thought could never happen in Nature is, in fact, a rather common occurrence and its mechanism is far more interesting than was ever envisioned.

Summary of talk by Dr.Eugene Nester at the University of Washington science colloquium.