Effects of cycloheximide, D-threo-chloramphenicol, erythromycin and actinomycin D on De-novo synthesis of cytoplasmic and mitochondrial proteins in the cotyledons of germinating pea seeds.

Inhibitors of, and radioactive substrates for, protein synthesis were introduced into germinating pea (Pisum sativum L.) seeds, and protein synthesis was allowed to proceed in vivo. Subsequent analyses of subcellular fractions showed the following: Cycloheximide strongly inhibited the incorporation of [(14)C]leucine into both mitochondrial and cytoplasmic proteins. D-Threo-chloramphenicol and erythromycin did not affect cytoplasmic protein synthesis, but partially inhibited mitochondrial protein synthesis. These results suggest that most of the new mitochondrial proteins were originally synthesized in the cytoplasm. Actinomycin D did not appreciably affect the initial incorporation of [(14)C]leucine into either mitochondrial or cytoplasmic proteins, suggesting that information (mRNA) concerning the initially synthesized proteins may be present in the quiescent seeds. The lack of appreciable incorporation of [(3)H]thymidine into mitochondrial DNA supported our previons report that mitochondria may not be synthesized de novo in pea cotyledons.