Molecular Characterization And Taurine Regulation Of CDO1 And CDO2 From Carassius Auratus

Cysteine dioxygenase(CDO)is a mononuclear nonhemoglobin enzyme that catalyzes the production of taurine through the cysteine(Cys)pathway and plays a key role in the biosynthesis of taurine in mammals.However,the function of CDOs in bony fish remains poorly understood.In this study,The PCR technology was used to amplify the open reading frame(ORF)sequence of CDO genes(CaCDO1 and CaCDO2)from the intestine of Carassius auratus.Analysis of the nucleotide sequence of the CaCDO1 and CaCDO2 genes showed that they encoded putative proteins with 201 amino acids respectively,which included structural features typical of the CDOs protein family-UDF 1637 structure domain.Multiple sequence alignment and phylogenetic analysis showed that CaCDO1 and CaCDO2 shared high sequence identities(98.5%,95.2%)and similarities(100.0%,95.7%)with C.carpio homologs.Quantitative real-time polymerase chain reaction(q RT-PCR)results revealed that CaCDO1 and CaCDO2 were both broadly expressed in all selected tissues and developmental stages in C.auratus.They have the highest mRNA expression level in intestine and liver,compared with the other tissues.Compared with the mRNA expression level of CaCDO1,the mRNA expression level of CaCDO2 was higher.To invest the effect of taurine on the mRNA expression of CDO in intestine of Carassius auratus,experiment in vivo and vitro were conducted.In vivo,Carassius auratus were feed vary level taurine.In addition,compared with control group,the in vivo mRNA expression levels of both CaCDO1 and CaCDO2 significantly decreased with increasing dietary taurine levels from 1.0 to9.0 g/kg.Furthermore,in vitro taurine treatments(10 mM,40 mM,60 mM,80 mM)showed similar inhibitory effects on the mRNA expression of CaCDO1 and CaCDO2 in the intestinal cell of C.auratus.Our results also showed that the mRNA expression of CaCDO2 in the intestines was significantly high than that of CaCDO1 in response to in vivo and in vitro taurine supplementation.Therefor,we suggested that CaCDO2 play an important role in the biosynthesis of taurine.Overall,these data mayprovide new insights into the regulation of fish CDO expression and provide valuable knowledge for improving dietary formulas in aquaculture.