Expression and inheritance of nine transgenes in rice

A total of 66 transgenic rice cell lines were produced by simultaneously transforming rice callus with nine different plasmids/genes. PCR analysis indicated that the co-transformation frequency of each gene was about 70%. All the cell lines carried at least three genes and 11 cell lines carried all nine genes. Thirty-two fertile transgenic plants (R-0) were generated from the transgenic cell lines and seeds of 32 transgenic R-1 lines and 5 R-2 lines were harvested and analyzed for gene inheritance and protein expression. Progeny segregation analysis indicated that the multiple transgenes were integrated into the same locus of the rice genome, resulting in a 3: 1 segregation ratio of the transgenes. Expression analysis of all nine transgenes revealed that the transgenes were expressed in all generations (R-0, R-1, and R-2) and about half of the transgenes from each line were expressed. The expression of one transgene appears to have no effect on the expression of another transgene. Among the 66 cell lines, six lines (9.1%) expressed seven or eight transgenes out of the nine transformed genes. All together, our results showed that multiple genes could be delivered into rice cells simultaneously and cell lines expressing multiple genes could be generated. The results and procedures reported here should be useful in designing multi-plasmid transformation experiments such as those required for plant metabolic engineering.