FIG. 5.
The effect of intercistronic length on the translation of the 5′-distal cistron in a dicistronic mRNA. Dicistronic mRNAs with GUS as the 5′-proximal cistron and luc as the 5′-distal cistron were constructed with intercistronic regions containing control sequence 17, 72, or 144 nt in length. Each capped mRNA construct was synthesized in vitro to terminate in a poly(A)50 tail. The 144-nt intercistronic region contains two copies of the 72-nt sequence present in the 72-nt intercistronic construct. The length of the control sequence (Con) included in each construct is indicated as a subscript. The 24-bp SL introduced into each construct is indicated diagrammatically. Expression from each mRNA following delivery to carrot protoplasts by electroporation or following translation in wheat germ lysate is shown to the right of each construct. Each mRNA construct was delivered to triplicate samples of protoplasts or translated in triplicate in vitro, and each sample was assayed in duplicate. The experiment was repeated a minimum of three times. The average value and standard deviation for the constructs of a typical experiment are reported.