A new potato virus in a new lineage of picorna-like viruses

On constructing a cDNA library for potato, ‘contaminating’ sequences with a significant identity to Apple latent spherical virus (ALSV) were found. Determination of the remaining genome sequence indicated the presence of a bipartite virus with an RNA1 and 2 of 7034 and 3315 nucleotides, respectively, excluding a poly(A)tail. RNA1 encodes a single polyprotein (233 kDa) and shares highest amino acid identity with ALSV at 65%. Conserved amino acid motifs typical for helicase, protease and RNA-dependent polymerase (RdRp) functions are present. RNA2 encodes a single polyprotein (106 kDa) with amino acid identities to the flat apple isolate of Cherry rasp leaf virus (CRLV-FA) (97%) and ALSV (70%), suggesting this is a potato strain of CRLV (CRLV-pot). Phylogenetic analysis using the RdRp region shows that this virus falls within a group separate from the Comoviridae that includes members of the Sequiviridae and the taxonomically unassigned viruses ALSV, Strawberry mottle virus, Satsuma dwarf virus and Navel orange infectious mottling virus. Other regions of the genome have highest identities with both plant and animal infecting members of the picorna-like virus superfamily. The evolutionary context of CRLV-pot and related viruses is discussed. Similar viral sequences from an EST library of peppermint are also analysed.