Viruses in the Phytoreovirus Genus of the Reoviridae Family have the Same Conserved Terminal Sequences

The 5′- and 3′-terminal nucleotide sequences of the dsRNA genome segments of rice dwarf virus (RDV) and rice gall dwarf virus (RGDV), members of the Phytoreovirus genus of the Reoviridae family, were determined and compared with those of wound tumour virus (WTV). The 3′ tetranucleotides of the plus strand of all genome segments of RDV and RGDV were found to be the same (---UGAU 3′), except for segment 9 of RDV which had the 3′-terminal sequence ---CGAU 3′. The conserved 3′-terminal sequence (---UGAU 3′) was the same as that found in the genome segments of WTV, another member of the Phytoreovirus genus. On the other hand, the 5′ termini of the plus strands of RDV and RGDV were found to have two or three types of common sequence. RDV had either 5′ GGCAAA--- or 5′ GGUAAA---, whereas RGDV had 5′ GGCAUUUU---, 5′ GGUAUUUU--- or 5′ GGUAAUUU---. These conserved sequences were similar to the conserved 5′-terminal sequence of WTV (5′ GGUAUU---). Although the three viruses differ in plant host range, tissue specificity, vector specificity and disease symptom expression, these results suggest that they have a common ancestral origin.