Subcellular localization of the 28 kDa protein of the triple-gene-block of bamboo mosaic potexvirus.

Open reading frame 2 of the bamboo mosaic potexvirus (BaMV) genome encodes a 28 kDa protein, the first of the "triple-gene-block' of BaMV which is believed to play a role in cell-to-cell movement of the virus in host plants. The 28 kDa protein was expressed in Escherichia coli and polyclonal antiserum was raised in a rabbit. Western blot analyses showed that the 28 kDa protein was associated mainly with components in the cell wall and 30000 g pellet fractions of a BaMV-infected leaf homogenate. Immunogold electron microscopy of infected leaf tissues revealed that the 28 kDa protein was associated with electron-dense crystal-line bodies (EDCBs) in the cytoplasm and nuclei. Nuclear EDCBs were found closely associated with nucleoli. Gold-labelled EDCB-like structures were also detected in the cytoplasm, but not within nuclei, in protoplasts up to 48 h post-inoculation. No specific labelling of the 28 kDa protein was found within any cytoplasmic structures or within cell walls.