Molecular cloning and sequencing of the capsid and the nuclear inclusion protein genes of a North American PVY(N) isolate

The sequence of the 3'-terminal 3258 nucleotides of a tobacco veinal necrosis strain of a potato virus Y (PVY(N))) isolate from North America was determined. The sequence revealed an open reading frame of 2931 nucleotides, of which the start codon was not identified. The nontranslated region contains 327 nucleotides upstream of a poly(A) tract. The open reading frame encodes a large polyprotein containing 976 amino acids. The data indicate that the coat protein (CP) and the nuclear inclusion protein (NIb) are derived from the large polypeptide by proteolytic cleavage similar to many other potyviruses. The putative cleavage sites of NIa/NIb and NIb/CP correspond to Q/A and Q/G sequences, respectively, as in other PVY(N) isolates. The CP and NIb contain 267 and 519 amino acid residues, respectively. Higher sequence homology of CP was observed with other PVY(N) isolates than with the PVY(O) isolates.