COMPLETE NUCLEOTIDE-SEQUENCE AND GENOME ORGANIZATION OF SWEET-POTATO FEATHERY MOTTLE VIRUS (S-STRAIN) GENOMIC RNA - THE LARGE CODING REGIONOF THE P1 GENE

The complete nucleotide sequence of a sweet potato feathery mottle vir us severe strain (SPFMV-S) genomic RNA was determined from overlapping cDNA clones and by directly sequencing viral RNA. The viral RNA genom e is 10 820 nucleotides long, excluding the poly(A) tail and contains one open reading frame (ORF) starting at nucleotide 118 and ending at 10 599, potentially encoding a polyprotein of 3 493 amino acids (Mr 39 3 800). The ORF was followed by a 3' untranslated region of 221 nucleo tides. The deduced polyprotein includes P1 (74K), HC-Pro (52K), P3 (46 K), 6K1, CI (72K), 6K2, NIa-VPg (22K), NIa-Pro (28K), NIb (60K) and co at (35K) proteins, after an analysis of protein cleavage sites analogo us to other potyvirus polyproteins. The polyprotein had a high level o f amino acid identity with those of other potyviruses, except in the r egions of P1 and P3. The P1 of SPFMV-S RNA has 664 amino acid residues , and is the largest and least similar to those of other potyviruses. HC-Pro and CI show high identity with those of other potyviruses. P3 h as relatively low identity, however, the length of P3 was within the r ange of variability among other potyviruses. The 6K1 protein between P 3 and C1 is also highly similar to those of other potyviruses. This is the first report on the complete nucleotide sequence of the sweet pot ato-infecting virus.