176 DYNAMIC INTERACTION OF INSERTED GENE PRODUCTS AND NATURALLY OCCURRING COMPOUNDS IN CRANBERRY.
The gene encoding β-glucuronidase, GUS, has been inserted into cranberry and is expressed in various tissues. Detectable expression of the GUS gene is enhanced up to 15x when the phenol-adsorbing compound, polyvinylpolypyrrolidone, is included in the extraction buffer of the fluorometric MUG assay, indicating that an endogenous, probably phenolic, compound is inactivating the foreign enzyme. Extracts from in vitro-grown cranberry leaves reduce the activity of purified β-glucuronidase in fluorometric assays. This is in contrast to extracts from other plants which have no affect on the enzyme. Detectable expression of the GUS gene for an individual transclone varies with the age of the tissue and the environment in which the plant is grown. The BT gene, which encodes for the Bacillus thuringiensis δ-endotoxin, was also inserted into cranberry with the purpose of incorporating lepidopteran insect resistance. Bioassays using an important insect pest on cranberry show generally inconsistent feeding patterns on transgenic plants. These results may be due to the interaction of the endogenous compounds and the B.t. δ-endotoxin.