Citrus exocortis viroid infection alters the in vitro pattern of protein phosphorylation of tomato leaf proteins.

The involvement of protein phosphorylation in the pathogenesis of citrus exocortis viroid (CEV) in tomato (Lycopersicon esculentum) plants was investigated by determining the pattern of protein phosphorylation after labeling with (γ- 32 P) ATP. The expression of this differential phosphorylation of proteins was Mn 2+ -dependent. These viroid-induced effects on protein phosphorylation could only be observed after disease symptoms had emerged in the plant