Submitted to: Archives of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 22, 2003
Publication Date: March 1, 2004
Citation: Stenger, D.C., French, R.C. 2004. Complete nucleotide sequence of oat necrotic mottle virus: a distinct tritimovirus most closel related to wheat streak mosaic virus. Archives Of Virology 149:633-640. Interpretive Summary: The complete genomic sequence of oat necrotic mottle virus (ONMV) was determined and found to be most closely related to wheat streak mosaic virus (WSMV), indicating that ONMV should be classified in the same genus as WSMV. Comparison of the two virus genomes indicated that protein cleavage sites were very similar, and that the predicted gene products of the two viruses were similar in number, size, and function. Analysis of variation within and between virus species suggests that ONMV has undergone directional selection during the course of speciation, whereas variation within strains of WSMV appears to have arisen through random genetic drift.
Technical Abstract: The RNA genome (9346 nucleotides) of Oat necrotic mottle virus (ONMV) was cloned and sequenced. Complete genome comparisons indicated that ONMV, currently classified as a rymovirus, was most closely related (~73% nucleotide, ~79% amino acid identity) to the tritimovirus Wheat streak mosaic virus (WSMV). ONMV encoded a single polyprotein, with proteinase cleavage sites very similar to those of WSMV. Pairwise comparison of ONMV and WSMV cistrons revealed that P3 was most conserved (~79% nucleotide, ~86% amino acid), whereas P1 was most divergent (~68% nucleotide, ~70% amino acid). These results firmly establish that ONMV is not a rymovirus but is instead a distinct species of the genus Tritimovirus. Analysis of sequence substitution patterns between ONMV and WSMV suggest that divergence among these viral species resulted from the accumulation of recurrent mutations at most variable sites, and that genetic distances between two species may underestimate branch lengths leading back to a most common ancestor. The inability of ONMV to infect wheat is most parsimoniously explained as a derived character state, with infection of wheat by other tritimoviruses representing the ancestral character state of the clade.