Myosins VIII and XI Play Distinct Roles in Reproduction and Transport of Tobacco Mosaic Virus

Viruses are obligatory parasites that depend on host Hula o for their replication as el as for their local and syst movement to establish infection. Although myosin motors are hought to contribute to plant virus infection, their exact role in the specific infection steps have not been addressed. Here we investigated the replication, cell-to-cell and systemic spread of Tobacco mosaic virus (TMV) using dominant negative inhibition of myosin activity. We found that interference with the functions of three class VIII myosins and two class XI myosins significantly reduced the local and long-distance transport o virus. We further determined that the inactivation of myosins XI-2 and XI-K affected the structure and dynamic behavior of th ER leading to aggregation of he viral movement protein (MP) and to a delay in the MP accumulation in plasmodesmata (PD) The inactivation of myosin XI-2 but not of myosin XI-K affected the localization pattern of the 126k replicase subunit and the level of TMV accumulation. The inhibition of myosins VIII-1, VIII-2 and VIII-B abolished MP localization to PD and caused its tention at the plasma membrane. These results suggest y he viral propagation and n racellular trafficking, whereas myosins VIII are specifically required for the MP targeting to and virus movement throu h the PD. Thus, TMV appears to recruit distinct myosins for different steps in the cell-to-cell p ad of the infection.