Sequence analysis of the 3' end of three Grapevine fleck virus-like viruses from grapevine

The 3' end of the genome of three Grapevine fleck virus-like viruses, i.e. Grapevine redglobe virus (GRGV), Grapevine asteroid mosaic-associated virus (GAMaV), and an unidentified virus from a Greek grapevine (accession GR8-19) was amplified from reverse transcribed total nucleic acid extracts from infected grapevine tissues and sequenced. The analysed genome portions differed in size and organization. The 3' ends of GAMaV (1852 nt) and of GR8-19 (1791 nt) resembled that of marafiviruses, as both encoded a single putative polyprotein containing the conserved "marafibox" sequence and lacked the stop codon between the replicase and coat protein genes. By contrast, the replicase and coat protein genes present in the terminal 2006 nt of GRGV genome were clearly separated and there was a 3'-proximal open reading frame encoding a putative proline rich protein with molecular mass of c. 17 kDa. The genome of all three viruses was polyadenylated. The organization of the 3' terminal genomic region and phylogenetic analysis of viral replicases and coat proteins suggest that GAMaV and the Greek virus GR8-19 belong in the genus Marafivirus, and GRGV in the genus Maculavirus, family Tymoviridae. Virus GR8-19 had molecular traits differing enough from GAMaV and other marafiviruses to be regarded as a new putative species in the genus Marafivirus, for which the name of Grapevine rupestris vein feathering virus is proposed.