Grafting Mediates Exchange of Genetic Information

Grafting is a method of asexual propagation widely used by plant breeders to modify plant architecture or introduce disease resistance. It can also occur naturally when shoots or roots of trees come into contact. It is generally believed that the grafted tissues maintain their genetic integrity, in that their genetic materials do not mix. But a team of researchers from the Max Planck Institute for Molecular Plant Physiology proved otherwise. By grafting tobacco plants expressing different marker genes, Sandra Stegemann and Ralph Bock showed that plants grafted together can exchange genetic information. The finding has important implications for grafting techniques and also provides a possible path for horizontal gene transfer.

"Our discovery of grafting-mediated gene transfer further blurs the boundary between natural gene transfer and genetic engineering and suggests that grafting provides an avenue for genes to cross species barriers," wrote the scientists in a paper published by Science.

Stegemann and Bock grafted two transgenic tobacco lines carrying different antibiotic resistance marker and fluorescent protein genes. One line carries the marker genes on its nuclear genome and the other carries the foreign genes on its chloroplast genome. The marker genes were found to be frequently exchanged between cells across the graft site. However, the scientists found that the transfer would only occur when the genes are carried in the chloroplast genome and that gene transfer is confined to the graft site and no long-distance transfer may occur.

The paper published by Science is available at http://dx.doi.org/10.1126/science.1170397