Ribosomal S6 kinase is activated as an early event in preemergence development of encysted embryos of Artemia salina

Dormant Artemia salina cysts contain desiccated gastrulae that are metabolically inactive, and physiologically arrested. Following rehydration, embryos resume development via alterations in protein expression, in the complete absence of cell division. In mammals, activation of p70 ribosomal S6 kinase (p70S6k) has been implicated in translational control, in particular the selective up‐regulation of translation of mRNAs with polypyrimidine tracts at their 5′ start sites. We therefore investigated ribosomal S6 kinase activity in preemergence development. We demonstrate that an S6 kinase activity is rapidly stimulated (within