Trypsin gene expression in adults and larvae of tropical gar Atractosteus tropicus.

Trypsin gene (try) expression levels were quantified in different organs of wild and captive tropical gar (Atractosteus tropicus) adults, and changes in expression during initial ontogeny of the species were determined. RNA was extracted from the pancreas, and cDNA was synthesized and later amplified by endpoint PCR using oligonucleotides designed from different try sequences of fish registered in GenBank. Subsequently, specific oligonucleotides were designed from the partial sequences. Gene expression was measured after RNA extraction and synthesis of the cDNA of 11 organs (liver, pancreas, stomach, esophagus, intestine, pyloric caeca, brain, muscle, gills, gonad, and kidney) of captive and wild adults. Likewise, samples of A. tropicus larvae were taken on days 0 (embryo), 5, 10, 15, 20, 25, and 30 days after hatching (DAH), the RNA was extracted, and the synthesis of cDNA was carried out to measure real-time gene expression (qPCR). The results showed that the highest relative try expression occurred mainly in the esophagus, liver, stomach, and pancreas of both wild and captive adult fish; however, captive organisms had a higher try expression level than wild fish. Although try expression during initial ontogeny was high in embryos (0 DAH), it did not reach the maximum value until 15 DAH. It was concluded that try expression levels in captive adults are due to the high protein content in the balanced feed (trout diet). The highest try expression level during larviculture was detected at 15 DAH, which indicates that A. tropicus larvae have a mature digestive system and can efficiently hydrolyze proteins from feed at this developmental stage.