THE PRESENCE AND SYNTHESIS OF THE NADPH-PROTOCHLOROPHYLLIDE OXIDOREDUCTASE IN BARLEY LEAVES WITH A HIGH TEMPERATURE-INDUCED DEFICIENCY OF PLASTID RIBOSOMES

High-temperature-induced deficiency of plastid ribosomes in barley plants (H. vulgare L.) was used as a system for studying the role of the cytoplasm in the synthesis of the NADPH-protochlorophyllide oxidoreductase. The enzyme is present in 33.degree. C-grown plants. The failure of high-temperature-grown plants to accumulate chlorophyll during illumination is not caused by the absence of the protochlorophyllide-reducing enzyme. The synthesis of the NADPH-protochlorophyllide oxidoreductase was studied by feeding [35S]methionine to the seedling and by following the incorporation of the radioactively labeled amino acid into plastid proteins. The NADPH-protochlorophyllide oxidoreductase was labeled in high-temperature-grown barley plants to the same extent as in control plants grown at 25.degree. C. Evidently, the 36,000-MW polypeptide of the NADPH-protochlorophyllide oxidoreductase is synthesized outside the plastid on cytoplasmic 80S ribosomes.