FIG 6.

Model for cell-to-cell movement of plant rhabdoviruses. Replication of nucleorhabdoviruses (tangerine) and cytorhabdoviruses (purple) occur in the nucleus or cytoplasm, respectively, and induce the formation of viroplasm (VP) sites of replication. Newly synthesized viral genomes in the VP are encapsidated by the nucleoprotein (N) and then associated with the phosphoprotein (P) and large polymerase protein (L) to form nucleocapsids (NCs), which are the minimal infectious units and movement entities. For nucleorhabdoviruses, the NCs must exit the nuclei prior to intercellular movement either by nuclear export activities or by de-envelopment of the intraluminal matured virions. The NC core N and P proteins then interact with membrane-associated P3 movement proteins (MPs) that guide intracellular NC trafficking to the cell periphery and intercellular transport through gated plasmodesmata (PD) across the cell wall (CW). Rhabdovirus movement is highly specific in requiring cognate MPs because of the species-specific MP-NC core protein interactions. Microtubule (MT)- and microfilament (MF)-associated proteins may also be involved in assisting NC trafficking.