CELL-TO-CELL MOVEMENT OF POTATO-VIRUS X REVEALED BY MICROINJECTION OFA VIRAL VECTOR TAGGED WITH THE BETA-GLUCURONIDASE GENE

The replication and cell-to-cell movement of potato virus X. (PVX) has been studied using a PVX vector construct which expressed the beta-gl ucuronidase (GUS) reporter gene in infected cells. Nicotiana cleveland ii leaf trichome cells were micro-injected with the PVX-GUS vector and histochemical staining was used to locate GUS activity. The distribut ion of GUS activity revealed that PVX had moved from the injected cell into other trichome cells and into the cells along the leaf margin. G US activity was always restricted to the cells at the edge of the leaf suggesting that PVX was unable to move out of the marginal cells. At the infection front, scattered along the leaf margin, there were isola ted groups of cells staining for GUS activity. The absence of GUS acti vity in the intervening cells suggests that PVX had moved through seve ral cells without replicating within them. This latter observation is consistent with previously reported observations that viral movement p roteins are capable of moving between cells.