The Period (per) Gene Plays an Important Role in Regulating Circadian Oscillation and Ovarian Development in the Ridgetail White Prawn, Exopalaemon carinicauda

Abstract

To explore the function of the period gene (Ec-per) in Exopalaemon carinicauda, we cloned the gene of 4611 bp with a 5′UTR of 201 bp, a 3′UTR of 813 bp, and an ORF of 3597 bp encoding 1198 amino acids. The predicted protein includes two PAS and one PERIOD domain. qPCR analysis revealed that Ec-per was expressed across all tissues tested at different developmental stages and during both embryonic and larval stages. Moreover, Ec-per oscillated rhythmically under different conditions of light-to-dark (L:D) ratios, including continuous darkness (0 L:24 D), where changes in the photoperiod influenced amplitude and phase shifts. The knockdown of Ec-per mRNA significantly reduced the expression of the circadian-related genes timeless (tim) and cryptochrome 1 (cry1) (p < 0.05). This suggests that Ec-per is an endogenous clock gene that may participate in molecular feedback loops and synergistically regulate the circadian rhythms through interacting with tim and cry1. RNA interference of Ec-per also markedly downregulated ecdysone receptor mRNA (p < 0.05), suggesting a positive role in the ovarian development of E. carinicauda. In situ hybridization further demonstrated that Ec-per is involved in oocyte proliferation and the accumulation of exogenous nutrients. This study provides new insights for promoting ovarian development and artificial breeding in crustaceans through optimized light-cycle management.