Plants grafted together exchange genetic information, suggesting a new and surprising mechanism for gene transfer between organisms.
Grafting is commonly used in cultivation and can occur naturally when shoots or roots from different trees come into contact, but grafting was not thought to involve any mixing of genetic material. To test this, Sandra Stegemann and Ralph Bock of the Max Planck Institute for Molecular Plant Physiology in Potsdam-Golm, Germany, grafted together two transgenic tobacco plants expressing different antibiotic-resistance genes.
The resistance genes were frequently exchanged between cells across the graft site. However, transfer only occurred when the genes were carried in the chloroplast genome, not when a resistance gene was inserted into the nuclear genome. Because the genetic exchange was limited to the graft site, the genes would only be passed to offspring of shoots formed at that site.