Cloning, sequencing, and mRNA expression patterns of GH and IGF-I genes in meagre (Argyrosomus regius) juveniles acclimated to different environmental salinities

Abstract

The Mediterranean meagre Argyrosomus regius exhibits a growing interest for aquaculture, presenting a good euryhaline capacity as well as enhanced growth under isosmotic environments. However, the role of growth hormone (GH)/insulin-like growth factor-I (IGF-I) axis mediating this euryhalinity is still completely unveiled. Therefore, and for the first time in this species, cDNAs of meagre’s pituitary growth hormone (gh), hepatic insulin-like growth factor (igf-1), and β-actin (actb) were cloned. Their mRNA expression patterns were tested in juveniles acclimated to 4 different environmental salinities: i) 5 ppt (hyposmotic, 140 mOsm kg?1H2O), ii) 12 ppt (isosmotic, 364 mOsm kg?1H2O), iii) 38 ppt (hyperosmotic; normal seawater, 1090 mOsm kg?1H2O), and iv) 55 ppt (extremely hyperosmotic, 1546 mOsm kg?1H2O). All nvestigated transcripts shared high sequence identities with their counterparts in other perciformes. gh mRNA enhanced significantly in both 12 and 55 ppt salinity groups in comparison to control group. However, igf-1showed its maximum expression levels under isosmotic salinity. The results indicated that growth enhancement observed in A. regius specimens under isosmotic environment is supported by the stimulation of GH/IGF-I axis.