Characterization of the coat protein gene of mite-transmitted blackcurrant reversion associated nepovirus.

The nucleotide sequence of the 3' terminal 3105 nucleotides (nt) of RNA2 of blackcurrant reversion associated virus (BRAV), the first mite-transmitted member of the nepovirus group, has been determined. The sequence contains an open reading frame of 1744 nt in the virus-sense strand, a 3' untranslated region of 1360 nt and a 3' poly(A) tail. Analysis of the amino-terminal residues of purified coat protein (CP) suggests that the CP gene is located between nts 1361 and 2959 (from the 3' terminus) in the RNA2, and that Asp/Ser is the proteolytic cleavage site of CP in the RNA2 encoded polyprotein. The predicted translation product from the CP gene is a polypeptide of 533 amino acids with a calculated Mr of 57 561. The amino acid sequence of BRAV CP showed highest similarity to blueberry leaf mottle virus (BLMV), and tomato ringspot virus (ToRSV), two members of the proposed sub-group three of nepoviruses possessing large RNA2 components. Nucleic and amino acid sequence comparisons between BRAV CP and the CPs of other nepoviruses indicate that specific conserved nepovirus CP domains occur in the BRAV CP thus confirming that BRAV is a member of the subgroup three of nepoviruses. reserved.