In this study we investigated whether in plants, like in mammals, components of the nuclear cap-binding protein complex (CBC) are involved in nonsense-mediated mRNA decay (NMD). We selected several genes producing at least two alternatively spliced mRNA variants: one with a premature termination codon (PTC+) and another without it (PTC–). For each gene the PTC+/PTC– ratio was calculated using RT-PCR and direct sequencing in four Arabidopsis thaliana lines: wild type, the NMD mutant atupf3-1and two CBC mutants: cbp20 and abh1. Whereas in the NMD mutant the ratios of PTC+/PTC– splice variants were higher than in wild-type plants, the two CBC mutants investigated showed no change in the PTC+/PTC– ratios. Our results suggest that neither CBP20 nor CBP80 is involved in NMD in A. thaliana.
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.