Sour cherry strain of plum pox potyvirus (PPV): Molecular and serological evidence for a new subgroup of PPV strains

Abstract

Properties of the unusual sour cherry strain of plum pox potyvirus (PPV-SoC) were investigated by sequencing its 3'-terminal 1,360 nt and examining its serological reactivity with several monoclonal antibodies (MAbs) to PPV. A significantly low degree of identity of the sequenced region has been found between PPV-SoC and other isolates of PPV. This is due to the high nucleotide divergence between the 5'-terminal region of the coat protein (CP) coding region of PPV-SoC and that of other isolates. Most nucleotide substitutions in the sequenced region are not silent and result in amino acid changes, especially near the N terminus of the CP. The unique 5' terminus of the PPV-SoC CP coding sequence has been utilized to develop a cRNA probe that hybridizes to PPV-SoC but not to other isolates/members of the D or M subgroups of PPV. The N-terminal region of the PPV-SoC CP contains the recognizable DAG motif that determines aphid transmissibility of potyviruses. Aphid transmission of PPV-SoC to herbaceous and woody hosts has been confirmed experimentally. Serological reactivity of PPV-SoC with 10 MAbs of PPV suggest that PPV-SoC represents a new serotype of PPV that does not fall into the conventional D or M serotypes/subgroups. We propose that PPV-SoC represents a new subgroup of PPV strains, termed PPV-cherry (PPV-C), and that PPV-SoC is its prototype member.