THE LOCATION OF THE 5' END OF THE POTATO LEAFROLL LUTEOVIRUS SUBGENOMIC COAT PROTEIN MESSENGER-RNA

Northern blot analysis of nucleic acid from potato plant tissues and tobacco protoplasts infected with a Scottish isolate of potato leafroll luteovirus (PLRV) detected the 6 kb genomic RNA and one subgenomic RNA species of about 2.7 kb; RNA extracted from virus particles contained only the genomic species. Blotting with small defined probes suggested that the location of the 5' end of the subgenomic RNA was between 2380 and 2510 nucleotides from the 3' end of the PLRV genome (between 3370 and 3500 nucleotides from the 5' end of PLRV Dutch isolate RNA). When RNA extracted from PLRV-infected or mock-inoculated protoplasts was used as the template for primer extension using primers complementary to the sequence at, or upstream of, the initiation codon of the coat protein gene, a single major infection-specific product was detected. A primer complementary to the sequence between 162 and 179 nucleotides upstream of the coat protein AUG yielded a product of 56 nucleotides. Thus, the subgenomic RNA has a leader sequence of 212 nucleotides, is 2505 nucleotides in length and starts at a position equivalent to 3376 nucleotides from the 5' end of the PLRV-Dutch genome, 11 nucleotides upstream of the termination codon of the putative polymerase gene. The nucleotide sequence immediately downstream of this position closely resembles that of the 5' end of the PLRV genomic RNA.