Virus-mediated export of chromosomal DNA in plants

The propensity of viruses to acquire genetic material from related species and from their hosts makes them potentially excellent vectors for horizontal gene transfer events. However, the acquisition of genetic material of the host organism from viruses has been inferred so far only from historical events and it is suspected to be a rare event. Here, we report spontaneous and surprisingly efficient generation of circular hybrid molecules made of virus and host DNA sequences. These molecules occurred in the form of minicircles during infection of Beta vulgaris plants by a singlestrand DNA virus belonging to the Geminiviridae family, i.e. Beet curly top Iran virus (BCTIV). These hybrid minicircles were able to replicate in plants, spreading systemically throughout the plants together with the viral infecting agent BCTIV, and were encapsidated into viral particles. Importantly, B. vulgaris DNA captured in minicircles could be multiplied also in other plant species sensitive to BCTIV infection, such as Nicotiana benthamiana and Arabidopsis thaliana, provided that BCTIV was present. In such tissue, B. vulgaris DNA captured in minicircles could also be transcribed. Conclusively, we document in real time the initial steps of a possible path of virus-mediated horizontal transfer of chromosomal DNA between plant species.