Flow of informational RNA from cytoplasmic poly(A)-containing particles to polyribosomes in Artemia salina cysts at early stages of development

Abstract

When Artemia salina cysts are incubated at 28°C in artificial seawater, the pool of cytoplasmic mRNA as measured by the [ 3H]poly(U) hybridization technique is depleted, and a parallel increase in the polysome bound mRNA is observed. The shift of informational RNA from subribosomal particles to polyribosomes occurs without a significant increase in the amount of poly(A)-containing RNA per embryo, at least during the first hours of development. In order to ascertain whether resumption of development is due mainly to utilization of preformed mRNA, the polypeptides synthesized in a wheat germ lysate under the direction of cyst cytoplasmic mRNA were compared with those obtained using polysomal mRNA from developed embryos (1 and 4 hr). The complex pattern of proteins synthesized in vitro was resolved into 70–80 radioactive spots by two-dimensional gel electrophoresis and was shown to be almost identical in unincubated and incubated cysts, except for a few novel spots. Our results do not exclude that early transcription of a few mRNA species could play a role in the activation of metabolic processes which occur when development is resumed.