Elevated ornithine decarboxylase activity and polyamine levels during early development in the brine shrimp Artemia franciscana

Abstract

AbstractRehydrated Artemia cysts were assayed for ornithine decarboxylase (ODC) activity and levels of putrescine, spermidine, and spermine during pre‐emergent development, emergence and hatching. Low but detectable ODC activity levels increased significantly within 2 hr, suggesting de novo synthesis of ODC protein and representing one of the earliest enzymatic biochemical markers in post dormancy development. ODC activity increased 100‐fold during preemergent development (occurring in the absence of an increase in tissue polyamine content). This increase in enzyme activity occurs in the relative absence of DNA synthesis but may be related to an enhanced polyamine synthetic capacity necessary for other physiological processes such as early transcriptional and translational activity. A second, higher ODC activity peak (correlated with a significant increase in polyamines) prior to hatching may be related to DNA synthesis and other biochemical processes associated with hatching of stage 1 nauplii and is correlated with increasing ecdysteroid titres reported previously. Putrescine and spermidine levels were significantly higher than spermine levels (2.5, 2.65, and 0.13 μmoles/g dry weight) at the onset of rehydration. High endogenous polyamines levels in encysted embryos are most likely available for use in metabolic processes associated with early differentiation. Polyamine levels increased significantly just prior to emergence and continued increasing throughout hatching. Spermidine to spermine ratios (>18) should reflect high rates of overall biosynthetic processes throughout preemergence, emergence, and hatching. © Wiley‐Liss, Inc.