Phytochrome‐Mediated Regulation of Two mRNAs, Encoded by Nuclei and Chloroplasts of Ribulose‐1,5‐bisphosphate Carboxylase/Oxygenase

Abstract
Etiolated pea [Pisum sativum cv. Alaska] seedlings (5 days old) were treated with red light for 5 min and grown for 2 days more in darkness. Effects of the red light on the mRNA levels of 2 subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39) (ribulose-P2 carboxylase), rate of enzyme synthesis and accumulation of the enzyme were examined for the plants. Increases of the 2 mRNA levels, encoded in nuclei and chloroplasts were observed. Red light followed by far-red light treatment for 5 min inhibited the increases. An increase parallel with the mRNA levels was found for the rate of the enzyme synthesis and accumulation of the enzyme. The induction of 2 mRNA levels is mediated by phytochrome and causes the red-light-inducible, far-red-light-reversible increase of ribulose-P2 carboxylase. When white light was irradiated to induce the enzyme, the effects of red light given in darkness were reinforced. Light-induction of ribulose-P2 carboxylase is mediated by phytochrome and controlled by the 2 mRNA levels.