Figure 6

Regulation of transcription from the promoter P rrn16 -118/-119 by cytokinin. (A) Analysis of 5'-ends of rrn16 transcripts by RNase Protection Assay (RPA, lane 1) and Reverse RNase Protection Assay (RePro, lanes 2, 3). RNA used for RePro was isolated from leaf chloroplasts, which were incubated either on water (H₂O, lane 2) or cytokinin (BA, lane 3). Mapped rrn16 transcription initiation site (filled circle) is identified by its distance between the transcription initiation site and the first nucleotide of the mature rRNA. Pup (open circle) denotes a signal of the size of the fully protected RNA probe possibly representing transcription initiation from an upstream promoter. Molecular weight marker in nt is provided on the side (M, lane 4). The scissors symbol denotes a RNA processing site. (B) Dot-blot analysis of a typical run-on reaction of chloroplasts isolated from leaves detached from 9-day-old barley plants which were incubated on water (H₂O) or cytokinin (BA) hybridized to rrn16 DNA fragments spotted in triplicates. (C) Relative rates of transcription for the rrn16 gene as determined by run-on analyses in (A) and RePro in (B). Data shown for the representative autoradiograms in (A) and (B) may slightly differ from the averages of multiple experiments shown in (C).