DIFFERENTIAL LOCALIZATION AND ACCUMULATION OF THE PLANT DOUBLE-STRANDED RNA-DEPENDENT PROTEIN-KINASE DURING VIRUS-INFECTION

Phosphorylation of the plant encoded, double-stranded (dsRNA)-dependen t protein kinase (pPKR) is significantly enhanced over basal levels du ring early phases of virus and viroid infection. It is unclear, howeve r, if corresponding pPKR protein levels are affected by pathogenesis. We now show that virus infection differentially effects pPKR protein l evels. Significantly, cytosolic associated pPKR protein levels are ind uced 3-5 fold compared to levels in extracts from mock inoculated leav es. However, ribosome-associated pPKR protein levels from virus infect ed tissues decreased approximately 4-fold relative to levels in extrac ts from mock inoculated tissues. Further, the level of cytosolic-assoc iated pPKR capable of binding to dsRNA declined during early TMV infec tion events suggesting that viral dsRNA's bind to pPKR in the cytosol during initial phases of pathogenesis. (C) Elsevier, Paris.