BEET SOIL-BORNE VIRUS-RNA-2 - SIMILARITIES AND DISSIMILARITIES TO THECOAT PROTEIN GENE-CARRYING RNA OF OTHER FUROVIRUSES

The complete sequence of the 3454 nt of RNA 2 of the Ahlum isolate of beet soil-borne furovirus (BSBV) has been determined starting with two short stretches of cloned cDNA, Unknown parts of the sequence were am plified by means of RT-PCR techniques using combinations of specific a nd random primers, BSBV RNA 2 is more similar in its genetic organizat ion to potato mop top virus (PMTV) RNA 3 than to any other furoviral R NA, although it is more than 1100 nt longer, Its 3'-end, unlike that o f PMTV RNA 3, has the potential to fold into a tRNA-like structure, It contains one large open reading frame for a readthrough protein with a molecular mass of 104 kDa (104K protein) which is interrupted intern ally by an amber stop codon terminating the coding region for a protei n of 19 kDa (19K), most likely the viral coat protein (CP), The readth rough domain of the 104K protein is much larger than that of PMTV, but the N- and C-proximal portions of these domains are similar for the t wo viruses, No serological relationships were found between the partic les of the two viruses, although more than 50% of the amino acid seque nces of the putative CPs are identical.