Liver type glycogen synthase (GYS2) and phosphorylase (PYGL) in largemouth bass (Micropterus salmoides): Cloning, characterization, and their transcriptional response to dietary carbohydrate content and resveratrol inclusion

Glycogen synthase (GS) and glycogen phosphorylase (GP) are considered as key enzymes involved in the regulation of glycogen synthesis and breakdown, respectively. In the present study, the liver type GS (GYS2) and GP (PYGL) of largemouth bass (Micropterus salmoides) were cloned and characterized, and meanwhile, their transcriptional expression in response to dietary carbohydrate levels and resveratrol inclusion, a non-flavonoid polyphenol involved in the regulation of glucose metabolism, was also investigated. Results showed that the full-length cDNA sequences of GYS2 and PYGL were 2477 bp and 3201 bp, which encoded 705 and 853 deduced amino acids, respectively. Gene sequence analysis revealed the conserved in evolution of GYS2 and PYGL. The GYS2 and PYGL of largemouth bass were both highly expressed in liver, rather than other detected tissues. The regulation of gene expression revealed that high dietary carbohydrate did not significantly impact the expression of GYS2, but significantly decreased the expression of PYGL. In addition, the supplementation of resveratrol significantly decreased the expression of GYS2, but significantly promoted the expression of PYGL, which partly accounted for beneficial role of resveratrol on alleviating hepatic glycogen accumulation in largemouth bass.