ASSOCIATION OF THE NONSTRUCTURAL P3 VIRAL PROTEIN WITH CYLINDRICAL INCLUSIONS IN POTYVIRUS-INFECTED CELLS

Antibodies raised against the 42K non-structural P3 protein encoded by the RNA genome of a potyvirus (tobacco vein mottling virus, TVMV) hav e been used with immunogold labelling procedures to determine the subc ellular location of P3 in infected Nicotiana tabacum cells. P3-specifi c gold label was found almost exclusively associated with the cylindri cal inclusions typically formed in the cytoplasm of polyvirus-infected cells by another non-structural viral protein, the cylindrical inclus ion protein. The P3 antibodies reacted with inclusions in both the tra nsverse (pinwheel-like) and longitudinal (bundle-like) orientations of these structures. Immunocytological examination of TVMV-infected prot oplasts showed the association of P3 with cylindrical inclusions durin g the early stages of formation of these structures and suggests that the P3 may be involved in the replication of potyviral RNA.