The Ri (root-inducing) plasmid of Agrobacterium rhizogenes carries agropine genes. When A. rhizogenes infects a plant, a portion of the Ri plasmid DNA enters the host plant cell and causes the production of hairy roots at the site of action. A foreign gene could be inserted into modified Ri plasmid and the recombinant DNA (plasmid) could be introduced into plants in much the same way as with the Ti plasmid of A. tumefaciens. The recombinant Ri plasmid would induce the production of hairy roots after the infection of the host plant. Scientists are now trying to use these hairy roots as potential drug factories. In a new study, scientists have successfully maintained a transgenic hairy root culture alive for 4-and-a-half years, and they hope that this could be a great source of continuous drug production. Read the full story here.