ISHS Acta Horticulturae 386: XVI International Symposium on Fruit Tree Virus diseases
COMPLETE NUCLEOTIDE SEQUENCE OF A PLUM POX POTYVIRUS ISOLATE (PPV-SC) DERIVING FROM SOUR CHERRIES AND INFLUENCE OF A COAT PROTEIN SEQUENCE MOTIF ON APHID TRANSMISSION |
| Authors: | E. Maiss, R. Casper, G. Deborré, W. Jelkmann |
| Abstract:
The complete nucleotide sequence of a non aphid transmissible plum pox potyvirus isolate (PPV-SC) deriving from sour cherries in Moldova (Verderevskaja, pers. comm.) has been determined after construction of a cDNA library. Comparison of different published PPV sequences with the PPV-SC sequence revealed a high degree of similarities in all functional proteins. Differences were found mainly in the genes coding for P1 and the coat protein. The coat protein was found to start with the amino acid valine instead of alanine. In addition the amino acid motif NAG was found close to the N-terminus of the coat protein, instead of DAG present in the coat protein of the aphid transmissible PPV isolates. A full-length cDNA of a non aphid transmissible isolate of plum pox virus (PPV-NAT) was constructed under the control of the 35S RNA promoter of CaMV to give p35SPPV-NAT. This clone proved to be infectious when mechanically inoculated onto different host plants. To evaluate the influence of the coat protein on the aphid transmission a part of the coat protein gene of the p35SPPV-NAT clone was replaced by the corresponding part of a PPV isolate from Germany (PPV-AT, aphid transmissible) and the PPV-SC isolate. The exchange led to an alteration of the sequence motif DAL in p35SPPV-NAT to DAG in p35SPPV-AT, suggesting that the helper component of PPV-NAT is functional. In addition site directed mutagenesis was carried out to mutate DAL (PPV-NAT) and NAG (PPV-SC), respectively, to DAG. These mutations restore the aphid transmissibility suggesting that the amino acid motif plays a crucial role in aphid transmission of PPV. Sequence analysis of the PPV-SC coat protein gene revealed a relationship to other D-type isolates. In addition D- and M-type isolates show a different folding of their coat proteins. | |
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