Uncut recombinant plasmids bearing nested cauliflower mosaic virus genomes infect plants by intragenomic recombination.

Experiments are described which show that recombinant plasmids bearing cauliflower mosaic virus genomes flanked by homologous viral DNA arms ('nested' viral genomes) can infect plants without prior excision of the CaMV genome. Infectious viral genomes are excised from such recombinant plasmids within the plant by a process of intramolecular recombination. The frequency of infection, and presumably recombination increase with the length of the homologous DNA flanking the CaMV genome. This mechanism affords us the opportunity to transfer directly the CaMV genome from bacteria to plants.