Deoxyribonucleic Acid-dependent Ribonucleic Acid Polymerase Activity of Nuclei and Plastids from Etiolated Peas and their Response to Red and Far Red Light in Vivo

DNA-dependent RNA polymerase activity has been found in both the nuclei and etioplasts of dark-grown pea seedlings (Pisum sativum). Although these enzymes had similar over-all characteristics with respect to substrate, pH, and inhibitor responses, they could be distinguished by their different sensitivities to sonication.Brief irradiation of the seedlings with red light resulted in an increase in the activity of both the nuclear and plastid enzymes, but the time course of this response showed it to be too slow to be considered an early result of phytochrome control of metabolism. Far red light following red treatment largely prevented the increase in the activity of the nuclear enzyme. The plastid enzyme responded to far red light in a manner similar to its response to red light so that no reversal was observed when far red treatment followed red.