Properties of the active plum pox potyvirus RNA polymerase complex in defined glycerol gradient fractions

As a first step in the study of the replication of plum pox virus (PPV) RNA, an in vitro virus-specific RNA polymerase activity was characterized in a crude membrane extract (Martin and Garcia, 1991). In this study, we report the fractionation of the crude membrane extract by centrifugation in glycerol gradients. The sedimentation properties after different treatments of the crude extract and its insensitivity to micrococcal nuclease treatment suggest that the RNA polymerase activity was localized in a defined and enclosed membranous structure. Subcellular membrane characterization of the different glycerol gradient fractions indicated that PPV-specific RNA synthesis occurred in fractions enriched in endoplasmic reticulum and tonoplast vesicles.