GENOTOXIN RESISTANCE PROPERTIES OF TRANSGENIC TOBACCO PLANTS EXPRESSING BACTERIOPHAGE-T4 DENV AND SACCHAROMYCES-CEREVISIAE APN1 PROTEINS

We have examined whether the resistance to genotoxic agents can be alt ered in transgenic plants by introducing heterologous DNA repair enzym es. Transformation of tobacco tissue produced two lines of plants, one expressing bacteriophage T4 UV endonuclease (DenV) and the other expr essing Saccharomyces cerevisiae apurinic-apyrimidinic endonuclease and 3'-diesterase (Apn1). Some of the transformants were subsequently cro ssed, with the expectation that Apn1 activity might complement DenV ac tivity in hybrid plants. Apn1 transgenotes behaved similarly to contro l plants upon exposure to UV-C light, oxidizing agents, or alkylating agents, as measured by chlorophyll bleaching. This is in contrast to p lants expressing DenV activity, which have been previously shown to ex hibit varying degrees of sensitivity to UV-C light and the alkylating agent dimethyl sulfate. APN1/denV hybrid plants were more sensitive to UV-C light than were parental lines, but reproducibly displayed enhan ced resistance to dimethyl sulfate. These data indicate that repair pr ocesses are an important component of natural protective systems in to bacco, because exogenous repair genes compromised the natural resistan ce of denV-transformed plants. In the hybrid plants, the two proteins appeared to act in concert, potentiating the effects of UV damage but enhancing the resistance to alkylation damage.