APHID TRANSMISSION OF A NON-APHID-TRANSMISSIBLE STRAIN OF ZUCCHINI YELLOW MOSAIC POTYVIRUS FROM TRANSGENIC PLANTS EXPRESSING THE CAPSID PROTEIN OF PLUM POX POTYVIRUS

Transgenic Nicotiana benthamiana plants expressing the coat protein of an aphid-transmissible strain of plum pox potyvirus (PPV) were infected by a non-aphid-transmissible strain of zucchini yellow mosaic potyvirus (ZYMV-NAT) in which the coat protein has a D-T-G amino acid triplet instead of the D-A-G triplet essential for aphid transmission. The aphid vector Myzus persicae could acquire and transmit ZYMV-NAT from these plants but not from infected N. benthamiana control plants that were not transformed or that were transformed but not expressing the PPV coat protein. The aphid-transmitted ZYMV subcultures were shown still to be non-aphid-transmissible from plants not expressing PPV coat protein, which indicated that their transmission was not due to RNA recombination or to reversion to the aphid-transmissible type. In immunosorbent electron microscopy experiments using the decoration technique, virus particles in the infected control plants could be coated only with ZYMV antibodies, while virus particles in the infected transgenic plants expressing the PPV coat protein could be coated not only with ZYMV antibodies but also in part with PPV antibodies. This suggests that aphid transmission of ZYMV-NAT occurred through heterologous encapsidation. These results indicate a potential risk of releasing genetically engineered plants into the environment.