Cloning of cryptochrome 1 gene and its expression characteristics analysis in Exopalamon carinicauda

Cryptochrome (Cry) is a kind of blue violet light receptor, which widely exists in animals, plants, bacteria and human body. At present, the research on cry mainlmainly focuses on its biological function, but rarely reported in crustacean biological rhythm. Exopalaemon carinicauda is a unique marine economic shrimp in China. Studying and understanding the circadian clock genes will help deepen the understanding of the biological clock regulation mechanism of crustaceans represented by E. carinicauda. The results showed that the full length of cry1 in E. carinicauda was 2 190 bp, the open reading frame was 1 845 bp, the 5 'noncoding region was 241 bp, and the 3' noncoding region was 104 bp. A total of 614 amino acids were translated. The predicted molecular weight of the protein was 70.5 ku and the theoretical isoelectric point was 5.09. After analyzing the amino acid sequence of Cry1, it was found that the Cry1 contains a structure homologous to DNA photolyase at 117-246 aa of N-terminal and a FAD binding domain at C-terminal. Homology analysis showed that the cry1 of E. carinicauda shared the highest homology with Litopenaeus vannamei and Euphausia superba (71.6% and 68.3%, respectively). Results of qRT-PCR analysis showed that cry1 of E. carinicauda was expressed in eyestalk, gill, heart, stomach, hepatopancreas, gonad, muscle, intestine and ventral cord nerve, and the expression level of eyestalk was the highest. The expression results at different time periods showed that the expression level of the cry1 in the eyestalks of E. carinicauda firstly decreased with the increase of the light time within 0-24 h, then began to increase after the lowest value at 9 h, and then decreased at 18 h. To the second trough, and finally re-entering the dark period, there is a significant increase again, and it was consistent with the more active rhythm of the E. carinicauda in the dark phase. After performing RNA interference under different light color conditions, the expression of cry1 in RNA interference group was significantly lower than that in control group under two light color conditions, which indicated that the expression of cry1 gene was successfully interfered in this study. The expression of cry1 in blue light was significantly higher than that in white light at 3-6 h after injection, but decreased at 9-24 h. The difference indicates that the cry1 is involved in the light signal transduction process under both blue and white light conditions, particularly involved in responding to the blue light periodic rhythm. This study provides a theoretical basis for in-depth exploration into the regulatory mechanism of crustacean circadian clock in the current situation where there is little research on crustacean circadian clock genes.