Depression of protein synthesis during diapause in embryos of the annual killifish Austrofundulus limnaeus

Rates of protein synthesis are substantially depressed in diapause II embry os of Austrofundulus limnaeus. Inhibition of oxygen consumption and heat di ssipation with cycloheximide indicates that 36% of the adenosine triphospha te (ATP) turnover in prediapausing embryos (8 d postfertilization [dpf]) is caused by protein synthesis; the contribution of protein synthesis to ATP turnover in diapause II embryos is negligible. In agreement with the metabo lic data, incorporation of amino acids (radio-labeled via (CO2)-C-14) into perchloric acid-precipitable protein decreases by over 93% in diapause II e mbryos compared with embryos at 8 dpf. This result represents a 36% reducti on in energy demand because of depression of protein synthesis during diapa use. Adjusting for changes in the specific radioactivity of the free amino acid pool at the whole-embryo level yields rates of protein synthesis that are artifactually high and not supportable by the observed rates of oxygen consumption and heat dissipation during diapause. This result indicates a r egionalized distribution of labeled amino acids likely dictated by a patter n of anterior to posterior cell cycle arrest. AMP/ATP ratios are strongly c orrelated with the decrease in rates of protein synthesis, which suggests a role for adenosine monophosphate (AMP) in the control of anabolic processe s. The major depression of protein synthesis during diapause II affords a c onsiderable reduction in energy demand and extends the duration of dormancy attainable in these embryos.