Figure 4.

Estimation of the minimum difference in mRNA accumulation between wild-type (WT) and synthetic (SYN) B.t.-toxin genes. Tobacco BY-2 protoplasts were electroporated with plasmids containing either wild-type or synthetic B.t.-toxin genes and plasmids containing a human β-globin gene as an internal standard. RNA from protoplasts expressing the synthetic B.t.-toxin gene was diluted in 2-fold steps up to 64-fold with total RNA from untransformed tobacco cells. Each lane was loaded with 20 μg of RNA. The positions of the B.t.-toxin and globin transcripts are indicated by arrowheads. The blot was hybridized with a probe specific for the rbcS-E9 3′ UTR common to all three transcripts. Dilution factors are indicated by numbers above the lanes.