Transcription of SCO1774 and SCO4157 during development of S. coelicolor , analysed by S1 nuclease protection. A. Transcription of SCO1774 in parent strain M145 and J2401 (whiA mutant). B. Transcription of SCO4157 in the parent strain M145, J2401 (whiA mutant) and J2408 (whiH mutant). M marks a lane with a DNA size marker (sizes given in bp). A lane containing a diluted sample of the probe, and another lane with a control reaction with yeast tRNA are indicated. Fragments corresponding to putative transcription start points just upstream of SCO1774 and SCO4157 are indicated by “P”. “R” indicates read-through transcription and “probe” indicates probe-probe reannealing products.