An N-proximal sequence of the alfalfa mosaic virus movement protein is necessary for association with cell walls in transgenic plants.

We have made transgenic tobacco plants (Nicotiana tabacum, cv. Xanthi nc) expressing the movement protein (P3, 300 amino acids) of alfalfa mosaic virus (A1MV) and two N-terminally deleted proteins lacking respectively 12 and 77 amino acids of the P3 sequence (P3 delta[1-12] and P3 delta[1-77]). The same proteins were expressed in recombinant yeast. By subcellular fractionation, the full-length P3 protein expressed by transgenic plants was found to be associated with cell walls as well as with cytoplasmic particulate material, as was the wild type movement protein expressed by A1MV-infected tobacco plants. P3 delta[1-12] behaved similarly but P3 delta[1-77] was found only in the cytoplasm. It thus appears that a polypeptide domain located between amino acids 13 and 77 of the P3 sequence is necessary for association of the protein with cell walls.