Okra mosaic virus empty protein shells in nuclei.

Okra mosaic virus produces large quantities (approximately 10 mg/g of tissue) of empty viral protein shells in inoculated cucumber cotyledons. Virus particles could not be detected in isolated nuclei, but empty protein shells accumulated there. At one day after inoculation, about half the total viral protein shells were found in the nucleus. This accumulation occurred in the presence of virus particles in the cytoplasm. The most likely explanation for this active and preferential accumulation is that viral coat protein enters the nucleus in the form of monomers or pentamers and hexamers, and is assembled into shells once inside.