The complete nucleotide sequences of the coat protein cistron and the 3' non-coding region of a newly-identified potyvirus infecting sweetpotato, as compared to those of sweetpotato feathery mottle virus

Complementary DNA representing 728 nucleotides of the 3' end of the genomic RNA of sweetpotato virus G (SPV-G) a newly-identified potyvirus infecting sweetpotato, was cloned and sequenced. This sequence was combined with that previously determined for the 5' terminal part of the coat protein cistron of the virus. The whole sequence contained a single open reading frame (ORF) of 1065 nucleotide, with the capacity to encode a coat protein of 355 amino acids, significantly larger than that of other potyviruses. The ORF was followed by an untranslated region of 222 nucleotides and a poly (A) tail. The coat protein of SPV-G was only distantly related to that of known potyviruses, with the exception of sweetpotato feathery mottle virus (SPFMV). Indeed, sequence identity in the C-terminal three quarters of the coat protein (more than 80%) and in the 3' untranslated region (more than 70%) indicate that SPV-G should be considered as closely related to, though distinct from SPFMV. This subset relationship is similar to that previously reported for members of the bean yellow mosaic virus subgroup or the bean common mosaic virus subgroup.