The genetic control of sea urchin development: A chromatographic study of protein synthesis in the <i>Arbacia punctulata</i> Embryo

Abstract

Abstract An analysis of the problem of embryonic differentiation in terms of protein synthesis was carried out in the embryo of Arbacia punctulata. The problem was approached with the technique of ion‐exchange chromatography of the embryonic proteins soluble in 0.5 M sodium chloride. Synthetic activity was measured as the incorporation of radioactive amino acids into protein fractions. It was seen that the complexity of the embryo's protein‐synthetic repertoire increases during early development indicating that differentiation at this level can be detected during early development. The antibiotic Actinomycin‐D was found to inhibit most of the specific protein syntheses during late development, while inhibiting fewer in early development. This indicates that most of the differential changes in early protein‐synthetic profiles occur under control of the readout of the embryo's stable messenger RNA. However, most differential changes associated with later development seem to be under control exerted at the gene level. Both translation‐level and transcription‐level control mechanisms appear to be active simultaneously at the stages of development analyzed. The inhibition of DNA‐dependent RNA synthesis, and of further differentiation beyond blastula, was found to be reversible, even after developmental arrest had occurred. The inhibition of protein synthesis was also reversible on removing embryos from the presence of the antibiotic. Since normal development and normal protein‐synthetic profiles are seen following this release of inhibition, it is concluded that there is no stringent requirement for the gene‐directed synthesis of any specific protein during the first 18 hours of development, in order for normal larval development to occur.