Circadian Clock Gene of Grass Carp (Ctenopharyngodon idellus): Genomic Structure and Tissue Expression Pattern of Period1 Gene

Background: Complex organisms require a sophisticated communication network to maintain circadian rhythmicity. Period (per) gene is an important circadian clock gene in vertebrates, playing important roles in several physiological processes, including locomotor activity, cell growth, reproduction, feeding behavior and hormonal secretion. However, little is known about the genomic structure and function of per gene in fish. Objective: The present study characterized the genomic structure and tissue expression of per1 gene in grass carp (Ctenopharyngodon idellus) for the first time. Method: Genomic structure of per1 was determined according to NCBI and ensemble database. Expression level of per1 mRNA was evaluated by real time PCR in different tissues of grass carp. Results and Conclusion: The obtained cDNA of per1a was 5003 bp consisted of 20 exons and 19 introns, and per1b was 5083 bp consisted of 19 exons and 18 introns in grass carp. Multiple sequence alignment and phylogenetic analyses indicated the orthology of mammalian, amphibian, reptile and fish per1. However, different gene arrangements of up- and down-stream of per genes were found among grass carp, zebrafish, medaka, stickleback, mouse and human. Tissue expression detection revealed wide distribution of per1a and per1b in grass carp. The conserved protein structure with mammals and highest expression in eye of grass carp per1b (p < 0.05) suggested its functions involved in rhythmic transcriptional regulatory and tropism movement to light in fish. These results could shed new light on the gene function and evolution of per gene in teleost.