Protein synthesis in the early Drosophila embryo; analysis of the protein species synthesized.

The soluble proteins were extracted from Drosophila eggs which had been permeabilitzed and incubated in medium containing [35S]methionine. These proteins were analysed on immunoelectrophoresis plates and on SDS polyarcylamide gels both by staining for total protein and by autoradiography. The radioactive proteins must have been synthesized during the period of incubation with [35S]methionine. In the period covered by this study (O-3 h) there was much protein synthesis but no new proteins were synthesized which had not already been synthesized during oogenesis. We conclude that the considerable protein synthesis that occurs in early Drosophila development is translated from maternal mRNA which is activated both by egg deposition and fertilization. Translation of protein from either masked maternal mRNA, which had not been previously translated, or from mRNA transcribed from the zygote genome must occur after blastoderm formation.