PROPERTIES OF THE ACTIVE PLUM POX POTYVIRUS RNA-POLYMERASE COMPLEX INDEFINED 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 characte rized in a crude membrane extract (Martin and Garcia, 1991). Zn this s tudy, we report the fractionation of the crude membrane extract by cen trifugation in glycerol gradients. The sedimentation properties after different treatments of the crude extract and its insensitivity to mic rococcal nuclease treatment suggest that the RNA polymerase activity w as localized in a defined and enclosed membranous structure. Subcellul ar membrane characterization of the different glycerol gradient fracti ons indicated that PPV-specific RNA synthesis occurred in fractions en riched in endoplasmic reticulum and tonoplast vesicles.