AMBISENSE SEGMENT-4 OF RICE STRIPE VIRUS - POSSIBLE EVOLUTIONARY RELATIONSHIP WITH PHLEBOVIRUSES AND UUKUVIRUSES (BUNYAVIRIDAE)

The complete nucleotide sequence of segment 4 of the rice stripe virus (RSV) genome was determined from overlapping cDNA clones and by direct RNA sequencing. The segment has two long open reading frames (ORFs). One of the ORFs (534 bases) is the 5' region of the viral sequence, and the other (858 bases) is in the viral complementary sequence of the viral 3' region. Such ambisense genome organizations have been seen previously in RNAs of phleboviruses, uukuviruses and arenaviruses. The ORF in the viral sequence encodes the major non-structural protein, but the product of the ORF in the viral complementary sequence (M(r) 32,407) has not yet been identified. The first 18 bases of each of the 5' and 3' ends of segment 4 are complementary in sequence. Among the 3'-terminal 16 bases, 14 were identical between RSV genome segments 3 and 4. These terminal sequences are very similar to those of RNAs of phleboviruses and uukuviruses. These and other characteristics indicate a possible evolutionary relationship between RSV and phleboviruses and/or uukuviruses.