CDNA cloning of artichoke mottled crinkle virus RNA and localization and sequencing of the coat protein gene

Abstract

We report the cDNA cloning of the genomic RNA of artichoke mottled crinkle virus (AMCV), which is a member of Tombusvirus group. AMCV has a monopartite positive sense RNA genome, which is not polyadenylated at the 3' end. The genome size is 4.8 kb. We have localized and sequenced the open reading frame (ORF) encoding the coat protein. Unlike most monopartite positive-strand RNA plant viruses, the ORF is not located near the 3' end, but like other members of the Tombusvirus group, CyRSV (cymbidium ringspot virus), TBSV-cherry (tomato bushy stunt virus cherry strain) and CNV (cucumber necrosis virus) it starts ca. 2.7 kb downstream of the 5' end and stops ca. 1 kb upstream of the 3' end. This ORF predicts a polypeptide chain of 387 amino acids. Comparison of the coat proteins of AMCV, TBSV-BS3, TBSV-cherry and CNV confirms that, within the Tombusvirus group, there exists a high degree of similarity among coat proteins but that this similarity is not uniformly distributed among domains. In particular, the N-terminal region, thought to make contact with the phosphate groups of the viral RNA, and the C-terminal region, considered the most immunogenic portion of the capsid, are found to be the least homologous.