Run-on transcription in WT and AS5ox chloroplasts. 250 or 500 ng of PCR product from chloroplast-encoded genes (right) were fixed to nylon membranes, with the chloroamphenicol acetyltransferase gene (cat) included as a negative control. Run-on transcription was conducted as described in Experimental Procedures. The ratio of AS5ox to WT transcription (left) was calculated after background subtraction of the cat gene and normalization to psbA. The average of three experiments is shown.