SEQUENCE-ANALYSIS OF THE 3' TERMINI OF RNA1 AND RNA2 OF BLUEBERRY LEAF MOTTLE VIRUS

The 3' termini of RNA1 and RNA2 of blueberry leaf mottle virus (BBLMV) were cloned and the cDNA sequence of a portion of the putative polyme rase gene, the complete coat protein (CP) gene, and the 3' non-coding regions was determined. The N terminus of the coat protein gene was pr ecisely located by comparison with the amino acid sequence determined by the Edman degradation sequencing of the purified coat protein. The coat protein gene encoded a polypeptide of 521 amino acids with a pred icted M(r) of 57,542. Homology to BBLMV coat protein was highest with tomato ringspot virus (TomRSV) and cherry leaf roll virus (CLRV); two other nepoviruses also belonging to a sub-group defined by the presenc e of large RNA2 components. The 3' terminal 1390 nt of RNA1 and RNA2 w ere nearly identical and apparently non-coding. No statistically signi ficant sequence homology was found between the 3' non-coding regions o f BBLMV and other nepoviruses. A highly conserved 3' non-coding region of this length is unusual, but has been reported for two other relate d viruses, TomRSV and CLRV. The biological function of the long 3' non -coding region and how the high level of sequence homology is maintain ed between RNA1 and RNA2, is unknown. Possible mechanisms for conserva tion of the 3' terminus are discussed.