THE ROLES OF THE CYLINDRICAL INCLUSION PROTEIN OF A POTYVIRUS IN THE INDUCTION OF VESICLES AND IN CELL-TO-CELL SPREAD

The in situ relationships between the cylindrical inclusion (CI) bodies of pea seedborne mosaic virus (PSbMV) and structures of the host cell are examined, and the function of the CI protein in virus-infected cells is considered. Of the three morphologies of the CI bodies of PSbMV, only the pinwheels (bundles in longitudinal section) are associated with cellular components. The bundles are associated with both the plasmodesmata and the membrane of the rough endoplasmic reticulum (rER). The rER associated with Cls produces large numbers of smooth-surfaced vesicles. Some of the vesicles, particularly those associated with the arms of the pinwheels, have electron-dense contents. The associations suggests two functions for the CI protein. The first is the induction of vesicles analogous to the 2BC protein of picornaviruses. The 2BC protein of poliovirus (a picornavirus) is known to associate with rER which responds by producing large numbers of smooth vesicles. The vesicular membranes provide a matrix to which the replication complex of poliovirus is bound. The second function is in the cell-to-cell spread of the virus. © 1990.