Novel insight in the virus-mediated export of plant chromosomal DNA.

The impact of the exchange of genetic material between organisms by means other than reproduction (horizontal gene transfer, HGT) on their evolution remains an open question. Due to the strict relationships established between viruses and hosts, these parasitic organisms are considered potential vectors of HGT events. Indeed, phylogenetic analyses have allowed to reconstruct historical events of HGT, showing the acquisition and exchange of genetic material not only between related viruses but also between viruses and their hosts. Nonetheless, events of transfer of genetic material from a host to a virus have been rarely reported in real time. We reported the rapid and efficient generation of circular hybrid molecules made of virus and host DNA sequences in sugar beet plants infected by the geminivirus beet curly top Iran virus (BCTIV),. Although non-replication competent, these hybrid molecules are trans-replicated by BCTIV, acting as helper virus and could spread systemically also in other BCTIV hosts, provided that BCTIV is present. New insight regarding the role of the host plant, BCTIV, and of the insect vector Circulifer haematoceps in the formation and spread of hybrid molecules will be presented. The relevance of these data on the virus-mediated horizontal transfer of chromosomal DNA between plant species will be discussed.