Plantibody-mediated inhibition of the Potato leafroll virus P1 protein reduces virus accumulation

The P1 protein of Potato leafroll virus (PLRV) is thought to play a major role in the replication cycle by promoting the maturation of the genome-linked virion protein VPg. To study the relevance of P1 and its autoproteolytic derivative P1-C25 in the viral life cycle, the VH and VL domains of monoclonal antibody mAbP1-1, raised against the C-terminus of P1, were used to develop a single chain variable fragment antibody scFvP1-1 for expression in plants. The transient expression of scFvP1-1 in tobacco (Nicotiana tabacum) strongly reduced virus accumulation, while transgenic potato (Solanum tuberosum) plants expressing scFvP1-1 showed high levels of resistance following PLRV inoculation by viruliferous aphids. This is the first report that conclusively demonstrates that a PLRV gene product is essential for the completion of the virus life cycle in vivo without genetic alteration of the viral genome. This is also the first time plantibody-mediated resistance has been demonstrated with a luteovirus.