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 infect ed by a non-aphid-transmissible strain of zucchini yellow mosaic potyv irus (ZYMV-NAT) in which the coat protein has a D-T-G amino acid tripl et instead of the D-A-G triplet essential for aphid transmission. The aphid vector Myzus persicae could acquire and transmit ZYMV-NAT from t hese plants but not from infected N. benthamiana control plants that w ere not transformed or that were transformed but not expressing the PP V coat protein. The aphid-transmitted ZYMV subcultures were shown stil l to be non-aphid-transmissible from plants not expressing PPV coat pr otein, which indicated that their transmission was not due to RNA reco mbination or to reversion to the aphid-transmissible type. In immunoso rbent electron microscopy experiments using the decoration technique, virus particles in the infected control plants could be coated only wi th ZYMV antibodies, while virus particles in the infected transgenic p lants expressing the PPV coat protein could be coated not only with ZY MV antibodies but also in part with PPV antibodies. This suggests that aphid transmission of ZYMV-NAT occurred through heterologous encapsid ation. These results indicate a potential risk of releasing geneticall y engineered plants into the environment.