Preformed mRNA and the programming of early embryo development.

A significant feature of the early development of fertilized echinoderm and amphibian eggs and germinating seed embryos is the utilization of genetic information that has been previously transcribed during oogenesis and seed ripening. When RNA synthesis is suppressed in the early developing embryos by actinomycin D, cordycepin, or alpha-amanitin, there is no effect on the translation of the "preformed mRNA", only a limited number have been thus far identified; microtubule and histone proteins in the fertilized sea urchin egg and carboxypeptidase and isocritric lyase in germinating cottonseed. Data obtained on the protein synthetic pattern at different times after the onset of development suggest that preformed mRNAs are made available to the translational system in a gradual process, thereby providing a molecular basis for the regulation of development. The possibility is considered that polyadenylation of mRNA, a reaction known to occur early after sea urchin fertilization, is responsible for regulating the release of preformed mRNA. It is shown that this reaction (polyadenylation) can be completely suppressed with little effect on the function of preformed mRNA. Finally, it is suggested, at least for the seed embryo system, that the formation of ATP may be a prerequisite for the activation of protein synthesis.