Phylogenetic Relationships Within the Family Potyviridae: Wheat Streak Mosaic Virus and Brome Streak Mosaic Virus Are Not Members of the Genus Rymovirus

Abstract

The complete nucleotide sequence of wheat streak mosaic virus (WSMV) has been determined based on complementary DNA clones derived from the 9,384-nucleotide (nt) RNA of the virus. The genome of WSMV has a 130-nt 5′ leader and 149-nt 3′-untranslated region and is polyadenylated at the 3′ end. WSMV RNA encodes a single polyprotein of 3,035 amino acid residues and has a deduced genome organization typical for a member of the family Potyviridae (5′-P1/HC-Pro/P3/6K1/CI/6K2/VPg-NIa/NIb/CP-3′). Because WSMV shares with ryegrass mosaic virus (RGMV) the biological property of transmission by eriophyid mites, WSMV has been assigned to the genus Rymovirus, of which RGMV is the type species. Phylogenetic analyses were conducted with complete polyprotein or NIb protein sequences of 11 members of the family Potyviridae, including viruses of monocots or dicots and viruses transmitted by aphids, whiteflies, and mites. WSMV and the monocot-infecting, mite-transmitted brome streak mosaic virus (BrSMV) are sister taxa and share a most recent common ancestor with the whitefly-transmitted sweet potato mild mottle virus, the type species of the proposed genus “Ipomovirus.” In contrast, RGMV shares a most recent common ancestor with aphid-transmitted species of the genus Potyvirus. These results indicate that WSMV and BrSMV should be classified within a new genus of the family Potyviridae and should not be considered species of the genus Rymovirus.

Wheat streak mosaic virus genotypes introduced to Argentina are closely related to isolates from the American Pacific Northwest and Australia

“…Wheat streak mosaic virus (WSMV) is the type species of the genus Tritimovirus in the family Potyviridae [17]. First reported from the Central Great Plains of the USA in the 1920s [12], WSMV is widely distributed in wheat-growing regions of North America and Eurasia.…”

“…A *1,267-bp fragment was amplified by PCR using the primers XV1 (5 0 -GATTCCGTTGAAGGATTTGTA ACTT-3 0 ) and XC1 (5 0 -AACCCACACATAGCTACCA AG-3 0 ) [6]. The amplified products correspond to WSMVSidney 81 nts 8,105-9,371 [17], encompassing the entire CP coding region (nts 8,189-9,238) and flanked upstream by the 3 0 -proximal portion of the nuclear inclusion b coding region and downstream by 3 0 -untranslated sequences. The amplicons were gel purified and cloned into pGEM-Teasy (Promega, Madison, WI).…”

Wheat streak mosaic virus Coat Protein Deletion Mutants Elicit More Severe Symptoms Than Wild-Type Virus in Multiple Cereal Hosts

“…WSMV is the type species of the genus Tritimovirus of the family Potyviridae with a 9,384-nucleotide positive-sense RNA genome [excluding the poly(A) tail at the 39 end] encapsidated in flexuous filamentous particles of 690 to 700 nm × 11 to 15 nm (Stenger et al 1998). The genomic RNA contains a single large open reading frame that encodes a polyprotein of 350 kDa and a P3N-PIPO protein of 32 kDa within the polyprotein (Fig.…”

“…Composed of 349-amino acid residues, WSMV CP is substantially longer, compared with, for example, the 267-amino acid residue long CP of Potato virus Y, which is the type member of the genus Potyvirus (Robaglia et al 1989;Stenger et al 1998). The CP of WSMV tolerates deletion of amino acids 6 to 27, 36 to 100, or the C-terminal 17 amino acids for systemic infection of wheat .…”

“…However, WSMV does not induce extensive leaf chlorosis in wheat under greenhouse conditions (Stenger et al 1998;Tatineni et al 2010). Plant viruses encode proteins for pathogenicity, including suppressors of RNA silencing (Pruss et al 1997;Voinnet et al 2000).…”