EXPRESSION AND INHERITANCE OF MULTIPLE TRANSGENES IN RICE PLANTS

The ability to control integration, inheritance, and expression of mul tiple transgenes is a prerequisite for manipulating biosynthetic pathw ays and complex agronomic characteristics in plants. One hundred and t wenty-five independent transgenic rice plants were regenerated after c obombarding embryogenic tissues with a mixture of 14 different pUC-bas ed plasmids. Eighty-five percent of the R0 plants contained more than two, and 17% more than nine, of the target genes. Plants containing mu ltiple transgenes displayed normal morphologies and 63% set viable see d. Multigene cotransformation efficiency was correlated with the ratio in which the plasmids were mixed with respect to the selectable marke r. All target genes had an equal chance of integration, indicating tha t the nature of the coding region had no effect on the efficiency of i ntegration. Three plant lines containing 11, 10, and 9 transgenes, res pectively, were analyzed for patterns of integration and inheritance u ntil the R3 generation. Integration of multiple transgenes occurred at either one or two genetic loci, with inheritance conforming to a 3:1 Mendelian ratio. Coexpression of four marker genes was investigated un til the R2 generation.