Transgenic tobacco plants expressing a truncated form of the PAMV capsid protein (CP) gene show CP-mediated resistance to potato aucuba mosaic virus

Four constructs of the potato aucuba mosaic virus (PAMV) coat protein (CP) gene were engineered for expression in tobacco plants: The full-length CP sequence (FL CP), two truncated forms--one at the N terminus (46 amino acid residues are deleted) (NT138), one in the conserved core portion (86 amino acids deleted) (CT258) of the gene--and an antisense RNA construct. These constructs were introduced into tobacco plants (Nicotiana tabacum) via Agrobacterium tumefaciens-mediated transformation. The plants transformed with the NT138 and FL CP constructs produced the mRNAs and proteins from the respective transgene. Transformants with the CT258 construct produced the transgenic mRNA, but the modified CP was not detected in the 20 different transformants tested. Transgenic R0 and R1 tobacco plants expressing the full-length, CT258, and the antisense constructs exhibited protection to PAMV infection and a delay in symptom development when inoculated with 0.1 and 0.5 microgram/ml of purified PAMV. Transgenic plants expressing the NT138 construct did not confer any detectable protection to PAMV infection. These results suggest that an engineered coat protein mediated resistance (CPMR) can be obtained from a CP gene truncated in its core region. The role of the N-terminal domain of the CP in the CPMR of PAMV and the implication of either the RNA or the protein in the protection is discussed.