1Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, CONICET, and Facultad de Ciencias Exactas y Naturales, UBA, Argentina; 2Instituto de Biotecnología, INTA (Castelar), and Facultad de Ciencias Exactas y Naturales, UBA, Argentina; 3Facultad de Ciencias Exactas y Naturales, UBA, Argentina
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Accepted 12 July 2001.
Tobacco plants were transformed with the open reading frame 3 gene from Potato virus X (PVX) coding for the p12 protein. Although the transgenic plants exhibited a normal morphological aspect, microscopic examination revealed extensive alterations in leaf tissue structure. After being challenged with PVX, the transgenic plants showed resistance to PVX infection and formation of specific leaf symptoms consisting of concentric rings encircled by necrotic borders. These novel symptoms were accompanied by biochemical changes normally associated with the hypersensitive response (HR) and were absent in noninfected transgenic plants or in PVX-infected nontransgenic plants. No equivalent virus resistance was observed after inoculation with Tobacco mosaic virus or Potato virus Y, suggesting the presence of a specific resistance mechanism. Despite development of HR-like symptoms, systemic acquired resistance was not induced in PVX-infected p12 transgenic plants. No evidence of an RNA-mediated resistance mechanism was found.
triple gene block,
© 2001 The American Phytopathological Society