Hormonal influence on amylase gene expression during Seabass (Lates calcarifer) larval development

alpha-Amylase gene expression was detected in newly hatched seabass (Lates calcarifer) larvae and peaked at around first feeding. This suggests a greater importance of carbohydrates during early larval development than might be expected for carnivorous fishes. In vivo cortisol and triiodothyronine (T(3)) treatment of seabass larvae upregulated alpha-amylase gene expression. The identification of a functional glucocorticoid-response element (GRE) on the amylase gene promoter indicates that cortisol (glucocorticoid) stimulation of amylase gene expression is direct via GRE. However no TRE (thyroid-response element) was found on the amylase gene and its promoter, and various concentrations of T(3) (1nM-10microM) also did not induce alpha-amylase gene promoter activity in rat AR42-J cells transfected with the promoter construct, unlike dexamethasone treatment. This suggests that T(3) stimulation of amylase gene expression in vivo was indirect, probably secondary to its promotion of one or more developmental processes.