Expression of alfalfa mosaic virus cDNA1 and 2 in transgenic tobacco plants.

Chimeric genes composed of DNA complementary to alfalfa mosaic virus (AIMV) RNAs 1 or 2, the CaMV 35 S promoter, and the nos polyadenylation signal were transferred to the genome of Nicotiana tabacum cv. Samsun NN by means of the Agrobacterium tumefaciens transformation system. Transformants contained intact copies of the viral genes and accumulated transcripts of approximately the size predicted from the cloning procedure. Using antisera raised against synthetic peptides corresponding to the C-terminal parts of AIMV P1 and P2, it was not possible to detect viral translation products in the transformants. However, transgenic protoplasts containing cDNA1 were able to complement an infection by the AIMV nucleoproteins containing RNAs 2 and 3, indicating that biologically active P1 accumulates in these protoplasts. Upon inoculation with AIMV strains 425 or YSMV, the cDNA1- and cDNA2-transformed plants became infected to a level similar to that of nontransformed or vector-transformed control plants.