Submitted to: Molecular Breeding
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/30/1998
Publication Date: N/A
Citation: Interpretive Summary: A major effort is underway around the world to develop virus disease resistant crop plants by expression of viral genes in plants. This approach has produced resistance. However, concern has been expressed about potential interactions between viral transgenes or their products with viruses, both homologous and heterologous, that might infect the transgenic plant. These and other concerns have led to stringent public regulation on environmental release of transgenic plants. The purpose of this work was to test experimentally the degree to which the potential for transgene/virus interactions in transgenic plants is actually realized with regard to specific interactions in potato plants transformed with specific CP or Rep gene constructs. These studies were extensive, and they did not detect evolution of new viruses in the transgenic potatoes, alterations in properties of viruses that commonly infect potato, infection of transgenic potatoes with viruses that do not infect the nontransgenic parent, or changes in reaction of plants to infection by heterologous viruses that commonly infect potato. These studies do not preclude the sorts of interactions searched for with the specific gene constructs used here or with other constructs but they suggest that their occurrence may be rare in the future and the risk of their occurrence may not be expanded by the fact that one of the genes is a transgene rather than a part of an infecting, intact virus.
Technical Abstract: A search was conducted to detect evidence for interactions between potato leafroll virus (PLRV)-derived transgenes expressed in Russet Burbank potato and viruses to which the transgenic plants were exposed and by which they were infected. More than 25,000 plants in 442 lines transformed with 16 different coat protein gene (CP) constructs and nearly 40,000 plants in 512 lines transformed with seven different replicase gene (Rep) constructs of PLRV were exposed to field infection over a 6-year period. These plants were individually inspected for type and severity of virus symptoms. Heterologous viruses found infecting the plants were identified and examined for alterations in transmission characteristics, serological affinity, host range, and symptoms. Selected isolates of PLRV from field-infected plants were examined for unusual symptoms produced in diagnostic hosts and for alteration in sedimentation properties in density gradient tubes. Viruses that were propagated in selected transgenic lines in a greenhouse were examined for similar alterations. Transmission characteristics and serological properties were not altered when they replicated in potatoes containing CP constructs in the field or greenhouse. Potato plants expressing CP or Rep constructs of PLRV were not infected in the field or in the greenhouse with viruses that do not normally infect potato. New viruses or viruses with altered sedimentation characteristics, symptoms, or host range were not detected in field-exposed or greenhouse-inoculated potato plants expressing CP or Rep gene constructs of PLRV.