The movement proteins (MP) of cowpea mosaic virus and cauliflower mosaic virus (CaMV) are associated with tubular structures in vivo which participate in the transmission of virus particles from cell to cell. Both proteins have been expressed in plant protoplasts and insect cells. In all cases, immunofluorescent histochemistry showed that the MPs accumulate intracellularly as tubular extensions projecting from the cell surface. Additionally, electron microscopy revealed intracellular MP aggregates in CaMV MP-expressing cells. The data presented establish common features for the tubule-forming MPs: no other virus gene products are required for tubule formation and unique plant components (e.g. plasmodesmata) are not essential for tubule synthesis.

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