Nucleotide sequences of genome segments S8, encoding a capsid protein, and S10, encoding a 36K protein, of rice gall dwarf virus

Abstract

The nucleotide sequences of DNAs complementary to the eighth (S8) and the tenth (S10) largest of the 12 genome segments of rice gall dwarf virus (RGDV) were determined. The S8 and S10 segments consist of 1578 and 1198 nucleotides, each with a single open reading frame extending for 1278 nucleotides from nucleotide 21, and 960 nucleotides from nucleotide 22, respectively. S8 encodes a polypeptide of 426 amino acids with an Mr of 47419. The amino acid sequences of several peptide fragments of the major outer capsid protein reported as 45K were contained in the predicted polypeptide. This protein, renamed the 47K protein, showed high homology with the outer capsid proteins of rice dwarf virus (RDV) and wound tumour virus (WTV); there was 56, 52 and 48% amino acid sequence identity between RGDV and WTV, RGDV and RDV, and RDV and WTV, respectively. S10 had the coding potential for a polypeptide of 320 amino acids with an Mr of 36,095 (36K protein), which exhibits 32% and 35% amino acid sequence identity with the predicted translation product of RDV S9 and the P9 capsid protein encoded by WTV S11, respectively. The conserved terminal sequences 5' GG...GAU 3' which are present in all genome segments of WTV and RDV so far analysed, and in S9 of RGDV, were also found in RGDV S8 and S10. This conserved sequence together with the segment-specific inverted repeats found in the terminal sequence of RGDV S8 and S10 are thus characteristic structures common to all three phytoreoviruses. The nucleotide sequence of the region surrounding the inverted repeats was more similar between RGDV and WTV than between RGDV and RDV.