THE COMPLETE GENOMIC STRUCTURE OF A SINGAPORE ISOLATE OF ODONTOLOSSUM RINGSPOT TOBAMOVIRUS

Abstract

A Singapore isolate of odontoglossum ringspot virus (ORSV-Sl) was obtained from Cattleya Lisa Ann. in Singapore. The complete sequence of ORSV-Sl comprised 6609 nucleotides and four open reading frames (ORFs 1 to 4). They are the 126/183 kDa RNA-dependent RNA polymerase (RdRp), 33 kDa movement protein and 18 kDa coat protein cistrons. The 5' untranslated region contained three copies of an eight base direct repeat and a (CAA)n motifs. Characteristic tRNA-like structure and pseudoknot structures were present in the 3' untranslated region. The genomic RNA and movement protein were one of the longest among all members of the tobamovirus group. Phylogenetic analysis of all four genes indicated evolutionary divergence, but within each gene there were some degrees of evolutionary convergence. The conserved amino acid sequences in the movement protein can be considered for the classification of tobamoviruses.