Cloning and molecular ontogeny of digestive enzymes in fed and food-deprived developing gilthead seabream (Sparus aurata) larvae.

ABSTRACT

We have determined the expression pattern of key pancreatic enzymes precursors (trypsinogen, try; chymotrypsinogen, ctrb; phospholipase A2, pla2; bile salt-activated lipase, cel; and α-amylase, amy2a) during the larval stage of gilthead seabream (Sparus aurata) up to 60days after hatching (dph). Previously, complete sequences of try, cel, and amy2a were cloned and phylogenetically analyzed. One new isoform was found for cel transcript (cel1b). Expression of all enzyme precursors was detected before the mouth opening. Expression of try and ctrb increased during the first days of development and then maintained high values with some fluctuations during the whole larval stage. The prolipases pla2 and cel1b increased from first-feeding with irregular fluctuation until the end of the experiment. Contrarily, cel1a maintained low expression values during most of the larval stage increasing at the end of the period. Nevertheless, cel1a expression was negligible as compared with cel1b. The expression of amy2a sharply increased during the first week followed by a gradual decrease. In addition, a food-deprivation experiment was performed to find the differences in relation to presence/absence of gut content after the opening of the mouth. The food-deprived larvae died at 10dph. The expression levels of all digestive enzymes increased up to 7dph, declining sharply afterwards. This expression pattern up to 7dph was the same observed in fed larvae, confirming the genetic programming during the early development. Main digestive enzymes in gilthead seabream larvae exhibited the same expression profiles than other marine fish with carnivorous preferences in their juvenile stages.