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A distinct caulimovirus, associated with dahlia mosaic, was cloned and sequenced. The caulimovirus, tentatively designated as dahlia common mosaic virus (DCMV), had a double-stranded DNA genome of ca. 8 kb. The genome organization of DCMV was found to be typical of members of the genus Caulimovirus and consisted of six major open reading frames (ORFs), ORFs I-VI, and one minor ORF, ORF VII. Sequence comparisons with the DNA genomes of two known caulimoviruses isolated from dahlia, Dahlia mosaic virus (DMV) and an endogenous caulimovirus, DMV-D10, showed that DCMV is a member of a distinct caulimovirus species, with sequence identities among various ORFs ranging from 25 to 80%.

ABTRACT: A new potexvirus affecting ornamental allium spp in the Netherlands was identified and characterized at the molecular level. The virus had a single-stranded RNA genome of 7100 bp (excluding the 18 bp poly A tail). The genome organization was found to be typical of members of the genus Potexvirus and consisted of five open reading frames (ORF). Nucleotide and amino acid sequence comparisons with those of known potexvirus members showed that this virus is related to Hosta virus X and Hydrangea ringspot virus. Sequence similarities and phylogenetic relationships suggested that the allium virus is a new and distinct species in the genus Potexvirus and the name, Allium virus X (AlVX) is proposed.

Plants of Triteleia hyacinthina, Triteleia ixioides Starlight, and Triteleia laxa Corina with severe mosaic and yellow vein-banding were found to be infected with a potyvirus. The 3′-terminal region of the virus was amplified by RT-PCR from total RNA using a potyvirus-specific degenerate primer (poty5P: 5′ GGN AAY AAY AGY GGN CAR CC 3′) and an oligo-dTprimer. The sequence generated included the 3′-NIb protein coding region (680 nucleotides), the entire coat protein coding region (840 nucleotides), and 3’-untranslated region (UTR) (253 nucleotides). Amino acid identity of the whole CP between the triteleia virus and potyvirus member ranged from 54% Apium virus Y (ApVY) to 67% Auraujia mosaic virus (ArjMV) and Twisted-stalk chlorotic streak virus (TSCSV) and the core ranged from 59% (ApVY) to 75% (ArjMV). The 3-UTR showed no significant homology with other known potyviruses. Phylogenetic relationships suggest this triteleia virus is a new member of the Potyvirus genus and the name of “Triteleia mosaic virus” (TriMV) is proposed. This is the first report of a potyvirus infecting triteleia.

RNA 3 of alfalfa mosaic virus (AMV) encodes the 5′-proximal movement protein (MP) gene and the 3′-proximal coat protein (CP) gene which is expressed from a subgenomic RNA. Several strategies were explored to use this RNA as a vector for expression of the green fluorescent protein (GFP) in Nicotiana tabaccum plants expressing the viral polymerase proteins P1 and P2 (P12 plants). Insertion of a subgenomic promoter (sgp)-GFP cassette between the CP gene and the 3′-untranslated region (UTR) interfered with RNA accumulation in protoplasts, indicating that cis-acting sequences required for replication were disrupted. When GFP was fused to the N-terminus of MP or CP, the chimeric RNAs accumulated in protoplasts but cell-to-cell movement in plants was blocked. Insertion of a GFP-sgp cassette immediately upstream of the CP gene caused a hypersensitive host response. However, insertion of a GFP-sgp cassette upstream of the MP gene did not affect symptom formation and yielded a vector that expressed GFP in inoculated but not in the systemic leaves of both P12 tobacco and non-transgenic N. benthamina plants. When the size of the GFP gene was reduced from 700 to 300 nucleotides, virus infection was observed in the non-inoculated leaves. Analysis of the progeny of some chimera revealed novel data on replication, encapsidation and recombination of AMV RNA 3.