Fig. 4.

The effect of the THI4 promoter on gene expression in vivo. RT-PCR analysis of luc transcript abundance in five independent lines of C. reinhardtii transformed with the luc gene under the control of the THI4 promoter (shown below the gel image) (A), a THI4 riboswitch-luc construct under the control of the THI4 promoter (B), or a THI4 riboswitch-luc construct under the control of the constitutive PSAD promoter (C). Cells were grown in the presence (+) or absence (−) of 10 μM thiamine. Primers were to the luc gene (LUC) or a constitutively expressed actin gene (ACT). Only those constructs with the THI4 riboswitch (B and C) showed thiamine responsiveness.