Nucleotide sequence of the tamarillo mosaic virus coat protein gene

Abstract

Tamarillo mosaic virus (TaMV), a member of the potyvirus group, causes yield loss and fruit blemishing in tamarillo (Cyphomandra betacea Sendt.) (1). Potyvirus genomes contain approximately 10 kb of a single stranded RNA and are translated as a polyprotein that is subsequently proteolytically cleaved. A cDNA clone covering the 3' terminus of TaMV (strain R) has been isolated and sequenced; part of this sequence is shown in the figure below. N-terminal sequencing of the first 10 amino acids of purified virus coat protein identified the beginning of the coat protein gene in the cDNA sequence (sequenced amino acids are underlined). The amino acid residues immediately upstream of the coat protein gene are homologous to proteolytic cleavage sites preceding the coat protein genes of other poty viruses (2, 3). T7 RNA transcripts were synthesized from a cDNA clone containing an in-frame AUG initiation codon immediately 5' of the coat protein gene. An in vitro translation product synthesized from this RNA comigrated with the native coat protein and was immunoprecipitated by antibodies raised against purified virus (data not shown). The TaMV coat protein shows 55—66% amino acid identity to the coat proteins of eleven distinct members of the potyvirus group. This level of homology suggests that TaMV is an independent member of the potyvirus group rather than a strain of an existing member (4). The TaMV 3' untranslated sequence shows less than 50% homology with other potyviruses, providing further support for this conclusion (5).