Terpenoid metabolism in plastids : sites of phytoene synthetase activity and synthesis in plant cells.

The biosynthesis of phytoene from prephytoene pyrophosphate has been localized exclusively in the plastid compartment of ruptured protoplasts derived from Triticum leaves and Capsicum fruits.The phytoene synthetase activity in Triticum leaves deficient in plastid ribosomes was comparable to those obtained in normal leaves. In addition, the stimulation of phytoene synthetase activity observed in green Capsicum fruit after 2-(4-chlorophenylthio)triethylamine hydrochloride treatment was not abolished by chlororamphenicol and lincomycin, in contrast to the inhibition observed after cycloheximide treatment.These data conclusively show that phytoene synthetase is localized exclusively in the plastid compartment in higher plants and that its synthesis is not performed on 70S ribosomes.