Virus-coded VPg protein of Potato virus Y (PVY) does not have homologs apart from other VPgs. Since VPg is indispensable for the potyvirus life cycle, it appeared a good candidate for eliciting pathogen-derived resistance to PVY. Following agroinfection used to obtain PVY VPg-transgenic Arabidopsis thaliana plants, only few transgenic seeds were recovered giving rise to six transgenic plants that contained the VPg gene with the correct sequence. They generated VPg mRNA, but VPg protein was not detected. Some plants were immune to PVY infection suggesting post-transcriptional gene silencing. However, the likely PVY VPg toxicity exerted at an early stage of transformed seeds development precludes its use for engineering pathogen-derived resistance
