Figure 8

Model for the role of the cileviruses MP in viral intracellular and intercellular transport. The cileviruses replication occurs in the membranes of endoplasmic reticulum (ER) resulting in larger viroplasms. A portion of the MP is transported into the nucleolus of the cell to bind to fibrillarin. The possibility to form a complex between MP plus fibrillarin that could exit the nucleus and interacts with vRNA and/or CP (p29) to form infectious vRNPs, is an open question. The MP, a membrane spanning protein, may anchors the vRNP complex to the ER membrane network, which traffics by the ER system to neighboring cells, facilitating the passage through plasmodesmata by the tubule formation. A possible alternative route may be mediated by the capacity of p29 to interact with MP and to associate with actin, thus anchoring the infectious complexes along the microfilaments (MF), guiding the vRNPs throughout the cytoplasm to the cell periphery. The virus particle is not required for the intercellular transport for this MP (indicating its capability to transport viral complexes different to virus particles intra and intercellularly); furthermore, the MP can transport the infectious complex cell-to-cell and systemically independent of the CP assistance. The redirection of p29 by MP to the plasmodesma could also be implicated to initiate viral replication in the newly infected cells.