Circadian-regulated expression of a nuclear-encoded plastid sigma factor gene (sigA) in wheat seedlings

The activity of a light-responsive psbD promoter in plastids is known to be regulated by a circadian clock, However, the mechanism of the circadian re gulation of the psbD light-responsive promotor, which is recognized by an E scherichia coli-type RNA polymerase, is not yet known. We examined the time course of mRNA accumulation of two E. coli-type RNA polymerase subunit gen es, sigA and rpoA, under a continuous light condition after 12 h light/12 h dark entrainment. Accumulation of the sigA mRNA was found to be regulated by a circadian clock, while rpoA mRNA did not show any significant oscillat ion throughout the experiment. (C) 1999 Federation of European Biochemical Societies.