Movement protein-derived resistance to triple gene block-containing plant viruses

Two mutant potato virus X (PVX) movement protein (MP) genes (m 12K-Sal and m 12K-Kpn) were obtained by inserting specific linkers at the boundary between the N-terminal hydrophobic and putative transmembrane segment, and the central invariant hydrophilic region of the respective 12 kDa, 12K, triple gene block (TGB) protein. Several transgenic potato lines which expressed m 12K-Sal or m 12K-Kpn to different degrees were resistant to infection by PVX, potato aucuba mosaic potexvirus and the carlaviruses potato virus M and S over a wide range of inoculum concentrations (3-300 micrograms/ml). However, they were not resistant to potato virus Y, which lacks a TGB protein. We suggest that the resistance of m 12K-Sal and m 12K-Kpn transgenic potato lines is MP-derived and not RNA-mediated.