NUCLEOTIDE-SEQUENCE OF RNA FROM THE SOBEMOVIRUS FOUND IN INFECTED COCKSFOOT SHOWS A LUTEOVIRUS-LIKE ARRANGEMENT OF THE PUTATIVE REPLICASE AND PROTEASE GENES

A virus found in naturally infected cocksfoot plants had a host range, symptom expression characteristics, and a particle morphology similar to those of cocksfoot mottle sobemovirus (CoMV). The viral RNA was cl oned and sequenced (GeneBank accession number L40905). Computer assist ed analysis of the 4,083-nt RNA sequence revealed four open reading fr ames (ORFs) flanked by 5'- and 3'-untranslated regions of 69 and 228 n t, respectively. The 3'-proximal ORF putatively coded for a 27.6-kDa p roduct that was obviously homologous to the coat proteins of southern bean mosaic sobemovirus (SBMV) and rice yellow mottle sobemovirus (RYM V), which agrees with the identification of this virus as a Russian is olate of CoMV. This virus genome is closely related to that of a recen tly sequenced Norwegian isolate of CoMV. The 5' end of the subgenomic RNA was mapped 35 nt upstream of the coat-protein ORF initiation codon . Despite the considerable sequence similarity of the CoMV coat protei n, putative RNA-dependent RNA polymerase (RDRP), and protease with the analogous proteins of SBMV and RYMV, CoMV differed from other sobemov iruses in the arrangement and expression of the RDRP and protease ORFs . The CoMV genome organization resembled those of the luteovirus genom es, i.e., the two ORFs overlap out of frame and are hypothesized to yi eld a frameshift fusion product.