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 (R dRp), 33-kDa movement protein (MP) and 18-kDa coat protein (CP) cistro ns are located at nt 63-3401/4901, 4807-5718, and 5721-6197 on the gen ome, respectively, The 5' UTR contains three copies of an 8-base direc t repeat and (CAA)(n) motifs. Characteristic tRNA-like structure and t hree consecutive homologous regions were present in the 3' UTR. The ge nomic RNA and MP of ORSV-S1 are one of the longest among all members o f the TOV group. Phylogenetic analysis of all four genes indicates evo lutionary divergence, but within each gene there are some degrees of e volutionary convergence. The conserved amino acid sequences in the MP can be used for the classification of tobamoviruses.