EXPRESSION OF THE COAT PROTEIN OF POTATO-VIRUS X FROM A DICISTRONIC MESSENGER-RNA IN TRANSGENIC POTATO PLANTS

Transgenic potato plants were generated which express a dicistronic mR NA corresponding to the 8 kDa protein and coat protein (CP) genes of p otato virus X (PVX). Northern blot analysis of RNA isolated from these plants indicated that both the 8 kDa protein and the CP are translate d from this dicistronic mRNA. Expression of both of these proteins in transgenic plants was demonstrated by Western blot analysis, and sugge sts that translation of CP takes place either by initiation by interna l entry of ribosomes or by a termination/reinitiation mechanism. CP wa s detected in protoplasts electroporated with RNA transcripts of the d icistronic construct in the presence or absence of a stable hairpin st ructure at the 5' terminus, suggesting that the former model is more l ikely. Similar results were obtained when a DNA fragment containing th e PVX CP leader sequence was placed between two reporter genes in the transient assay system. These results suggest that potexvirus CP expre ssion may take place from the genomic RNA as well as from the subgenom ic RNA.