The early secretory pathway and an actin-myosin VIII motility system are required for plasmodesmatal localization of the NSvc4 protein of Rice stripe virus

Plant viruses utilize movement proteins to gain access to plasmodesmata (PD) for cell-to-cell propagation. While the NSvc4 protein of Rice stripe virus (RSV) is implicated in the passage of viruses from cell to cell, its role remains to be elucidated. We examined the mechanisms by which RSV NSvc4 is targeted to PD in cell walls. NSvc4 accumulated at PD when expressed as a fusion with yellow fluorescent protein in leaf cells of Nicotiana benthamiana. NSvc4 was targeted to PD via the endoplasmic reticulum-to-Golgi secretory pathway, and the actomyosin motility system was required for the delivery of NSvc4 to PD. Moreover, it appeared that NSvc4 utilized myosin VIII-1 rather than myosin XI for trafficking to PD. Taken together, our data reveal that the targeting of NSvc4 to PD exploits the early secretory pathway and the actin-myosin VIII motility system in the leaves of a non-host plant, N. benthamiana.