Coat Protein Properties Indicate That Maize Dwarf Mosaic Virus-KS1 Is a Strain of Johnsongrass Mosaic Virus

Abstract

It has recently been shown that 17 potyvirus isolates infecting maize, sorghum, and sugarcane in Australia and the United States, and previously classified as strains of sugarcane mosaic virus (SCMV), belong to four distinct potyviruses. However, the taxonomic status of other SCMV strains is uncertain at present. Using amino acid composition, high-performance liquid chromatographic peptide profiling of tryptic digests, partial amino acid sequence data, and electro-blot immunoassay of coat proteins, we confirm that the oat-infecting strain of maize dwarf mosaic virus (MDMV-O) from the United States is structurally and serologically closely related to the Australian johnsongrass strain of johnsongrass mosaic virus (JGMV-JG). Our results further show that the coat protein of the Kansas strain of maize dwarf mosaic virus (MDMV-KS1) is nearly identical to that of MDMV-O. Coat protein from both MDMV strains differs from the JGMV-JG coat protein by about 20 amino acid residues. The majority of amino acid substitutions occurred in the surface-exposed amino terminal region. B analogy with the observations that strains of potyviruses exhibit high-coat protein sequence identity, these results demonstrate that MDMV-O and MDMV-KS1 are strains of JGMV.