A comparative study of the cowpea and bean strains of southern bean mosaic virus.

Features of the primary structure and translation of the genomic RNAs of the cowpea and bean strains of southern bean mosaic virus have been investigated in order to assess the similarity of the two viruses. The sequence of 400 bases at their 3' termini have been determined. These include the 3' noncoding regions and extend well into the coat protein cistrons. The noncoding regions (136 bases for the cowpea strain RNA and 129 bases for the bean strain RNA) show no obvious sequence homology. However, extensive base as well as amino acid sequence homology exists in the coding region. RNAs from both strains have a small protein attached to their 5' terminus-the protein in the cowpea strain being the smaller of the two. In vitro studies show that there are similarities in the overall mode of translation of the genomes of the two viruses. Although corresponding proteins are synthesized they differ in size.