Temporal regulation of tobacco mosaic virus-induced phosphorylation of a host encoded protein.

The in vitro and in vivo phosphorylation of a plant encoded protein (p68) associated with dsRNA-dependent protein kinase activity was stimulated at specific time intervals following infection by tobacco mosaic virus or electroporation with dsRNA. The level of p68 phosphorylation in infected and mock inoculated protoplasts did not differ significantly until 6 hr. post-infection, when the basal level of phosphorylation increased 2-3 fold in infected protoplasts. Maximum phosphorylation of p68 occurred between 8-12 hr post-infection and then declined but, at least until 72 hr. post-infection, it was significantly greater than in mock inoculated protoplasts.