Characterization of Potato virus Y (PVY) molecular determinants involved in the vein necrosis symptom induced by PVYN isolates in infected Nicotiana tabacum cv. Xanthi.

Viral molecular determinant(s) involved in the tobacco vein necrosis (TVN) symptom induced by necrotic isolates of Potato virus Y (PVY) on Nicotiana tabacum cv. Xanthi leaves remain undetermined. Reference isolates belonging to PVY(N) (infectious PVY(N)-605 clone) and PVY(O) (PVY(O)-139) were used to produce PVY chimeric genomes by using reverse-genetic techniques. These chimeric clones were inoculated biolistically onto Nicotiana clevelandii plants to establish the clone, prior to being tested on N. tabacum for their ability to induce TVN symptoms. Comparison between sequence data and symptoms observed for each mutated PVY construct shows that the C-terminal part of the multifunctional HC-Pro protein includes two residues (K(400) and E(419)) that are involved in TVN induced by PVY(N) isolates. Site-directed mutagenesis was used to confirm that these two HC-Pro residues are involved in the TVN phenotype.