Arrest of cytochrome-c oxidase synthesis coordinated with catabolic arrest in dormant Artemia embryos
Abstract
We have examined cytochrome-c oxidase (COX) biosynthesis in brine shrimp (Artemia franciscana) embryos during preemergence development (PED), as well as its inhibition under anaerobic dormancy, to determine whether transitions in intracellular pH (pH(i)) have a regulatory influence on anabolic processes. Under control aerobic conditions (embryo pH(i) ≥ 7.9), incorporation of radiolabeled amino acids shows that substantial biosynthesis of COX occurs during 12 h of PED (500% increase when corrected for enzyme turnover). This anabolic process is blocked under anoxia, a condition known to foster intracellular acidification (pH(i) ≤ 6.8). The arrest of COX synthesis is quantitatively identical when embryos are incubated aerobically during artificial acidification with CO2 (pH(i) = 6.8). The data suggest that pH(i), directly or indirectly, is a regulator of protein synthesis in Artemia embryos during anaerobic dormancy. Previous work has established a fundamental role for pH(i) in the arrest of carbohydrate catabolism under anoxia. Thus there appears to be a coordinated suppression of energy-producing and energy-utilizing events as Artemia embryos enter quiescence that involves pH(i) as the common intracellular signal.