Complete nucleotide sequences and genome characterization of double-stranded RNA 1 and RNA 2 in the Raphanus sativus-root cv. Yipinghong

Four distinct double-stranded (ds) RNA bands were extracted from leaves of Raphanus sativus-root cv. Yipinghong with yellowing at the leaf edge in China. Purified viral particles of 28-30 nm in diameter contained dsRNA segments with the same number and mobility as these extracted directly from radish leaves. The two major dsRNA segments, namely RasR 1 and RasR 2, were 1866 and 1791 bp in length, respectively. Computer analysis predicted that they both contained a single open reading frame (ORF) on their plus-stranded RNA, putatively encoding a RNA dependent RNA polymerase and a capsid protein similar to that encoded by members of the family Partitiviridae. In addition, both RasR 1 and RasR 2 were highly conserved at the 5' untranslated regions (UTR) and had an adenosine-uracil rich stretch at the 3' UTR, with an identical terminal motif (5'-AAAAUAAAACC-3'). Taken together, these results suggest that the two major dsRNA segments constitute the genome of a partitivirus infecting radish.