CHARACTERIZATION OF COCKSFOOT MOTTLE SOBEMOVIRUS GENOMIC RNA AND SEQUENCE COMPARISON WITH RELATED VIRUSES

The genome of cocksfoot mottle virus (CfMV) is a positive-sense ssRNA molecule of 4082 nucleotides as revealed by sequencing the entire geno me. The 5'-untranslated region of the genome is 69 nucleotides and the 3'-untranslated region is 225 nucleotides in length. The coding regio n contains four open reading frames (ORFs). The organization of CfMV O RFs differs significantly from that of the previously sequenced sobemo viruses southern bean mosaic virus and rice yellow mottle virus. ORF1 encodes a protein having a calculated molecular mass of 12.3 kDa. The function of this protein is unknown. The next ORF codes for the putati ve VPg and serine protease. The ORF2a product consists of 568 amino ac ids, with a calculated molecular mass of 60.9 kDa. The replicase of Cf MV is translated as part of a polyprotein by -1 ribosomal frameshiftin g in ORF2a. The calculated molecular mass of the transframe protein is 103.4 kDa. ORF3 encodes the 27.6 kDa coat protein. This has been veri fied by amino acid sequencing of the CfMV coat protein N terminus. Nor thern blots of total RNA from CfMV-infected barley leaves reveal the 4 .1 kb genomic RNA band and one virus-specific band of 1.2 kb, which ma y represent a subgenomic RNA for coat protein synthesis.