Cloning and expression analysis of OPN5 gene in Lateolabrax maculatus under different photoperiodic treatments

【Objective】By cloning the L. maculatus opsin(OPN5) gene(LmOPN5) sequence to investigate the expression level of LmOPN5 gene in retina,saccus vasculosus,hypothalamus,and pituitary of L. maculatus under different photoperiods,the purpose of this study was to explore the influence of photoperiod on the expression level and expression pattern of LmOPN5 gene,which provided reference for further study of L. maculatus sensing photoperiod signal.【Method】Firstly,the full-length sequence of LmOPN5 gene was obtained by PCR and RACE,and bioinformatics analysis was performed. Then,real-time fluorescence quantitative PCR was used to compare the relative expression of LmOPN5 gene in different tissues. Finally,different photoperiods(normal treatment group 12 L∶12 D; short photoperiod 8 L∶16D; long photoperiod 16 L∶8 D. L∶light time,D:dark time) on LmOPN5 gene expression in retina,saccus vasculosus,hypothalamus and pituitary. 【Result】The length of LmOPN5 gene cDNA was 1732 bp,and the full length open reading frame(ORF) was 1056 bp,encoding 351 amino acids residues. The molecular weight was 39.26 kD,and the theoretical isoelectric point(p I) was 9.17. The results of protein secondary structure analysis showed that LmOPN5 proteins mainly contained four stuctures: α-helix(40.17%),irregular coil(34.76%),extended chain(22.51%),and β-turn(2.56%). Therefore,the proteins were mainly composed of irregular coil and α-helix. Homology comparison analysis of amino acid sequences showed that the similarity between LmOPN5 amino acid sequence and OPN5 amino acid sequence of other bony fishes ranged from 82.7% to 92.0%,and the similarity with OPN5 of mammals was low. LmOPN5 gene was more widely distributed in brain tissues,with higher relative expression levels in hypothalamus,optic lobe,pituitary,telencephalon and saccus vasculosus. At the same time,it was also highly expressed in the retina of the eye. In the retina,the relative expression of LmOPN5 gene changed significantly under different photoperiod treatments(P<0.05, the same below). Long photoperiod promoted the expression of LmOPN5 gene,while short photoperiod inhibited the expression of LmOPN5 gene. In the saccus vasculosus,the expression of LmOPN5 gene in long photoperiod treatment was significantly higher than that in normal photoperiod treatment. In hypothalamus,the expression of LmOPN5 gene did not change significantly under the three photoperiod treatments(P>0.05). In pituitary,the expression of LmOPN5 gene in short photoperiod treatment was significantly higher than that in long photoperiod treatment and normal treatment. 【Conclusion】LmOPN5 gene sequence is conserved in bony fish species. Different photoperiod treatments affect the expression of LmOPN5 gene in retina,saccus vasculosus and pituitary. The results indicate that the photoperiod response of different tissues of L. maculatus is not consistent,and the sensitivity of L. maculatus to photoperiod is tissue-specific.