Intracellular localization of TEV capsid and inclusion proteins by immunogold labeling

Thin sections of tobacco etch virus (TEV)-infected leaves were treated with goat anti-rabbit antibodies conjugated to 15-nm gold particles after the sections had been exposed to rabbit antisera specific to virus particles, virus capsid, 70K CI protein, 54K NI protein, or 49K NI protein. Anti-TEV or anti-TEV capsid sera specifically detected virus particles and capsid protein in the cytoplasm and capsid protein which was also found arrayed in a regular fashion adjacent to the cell wall. The NI 54K and 49K inclusions were found primarily in the nucleus and surprisingly in the cytoplasm. Free NI 54K and 49K proteins were also found in regions adjacent to the nuclear membrane and in association with the nucleolus. The 70K CI protein was found in the pinwheel inclusions and laminated aggregates as well as filamentous structures associated with the cell membrane. The latter observation is significant in view of the hypothesis that the 70K CI protein represents the membrane binding component of the viral replication complex.