The complete sequence of a Singapore isolate of odontoglossum ringspot virus and comparison with other tobamoviruses

The complete sequence of a Singapore isolate of odontoglossum ringspot virus (ORSV-S1) comprises 6609 nucleotides (nt) and four open reading frames (ORFs 1 to 4). The 126/183-kDa RNA-dependent RNA polymerase (RdRp), 33-kDa movement protein (MP) and 18-kDa coat protein (CP) cistrons are located at nt 63-3401/4901, 4807–5718, and 5721–6197 on the genome, respectively. The 5′ UTR contains three copies of an 8-base direct repeat and (CAA) n motifs. Characteristic tRNA-like structure and three consecutive homologous regions were present in the 3′ UTR. The genomic RNA and MP of ORSV-S1 are one of the longest among all members of the TOV group. Phylogenetic analysis of all four genes indicates evolutionary divergence, but within each gene there are some degrees of evolutionary convergence. The conserved amino acid sequences in the MP can be used for the classification of tobamoviruses.