Diurnal pattern of phosphoenolpyruvate carboxylase ( Pepc ). Quantification of (A) Pepc hnRNA and (B) Pepc mRNA through one day/night cycle. Numbers are units relative to levels in leaves harvested 4 h after illumination. The orange line shows the transcription level in re-etiolated leaves (lowest Pepc promoter activity) for comparison. (C) Comparison of hnRNA levels and RNA Polymerase II abundance in the Pepc coding region. Data points are based on at least three independent experiments. Vertical lines indicate standard errors.