Association of Single Nucleotide Polymorphisms in Cysteamine Dioxygenase Gene with Taurine Content in Oyster Crassostrea gigas

The Pacific oyster Crassostrea gigas is rich in taurine, a conditionally essential amino acid functioning in anti-oxidation, anti-inflammation, anti-aging, osmoregulation, and neuromodulation. Breeding oyster varieties with enhanced taurine content is significant to meet people’s demand for high-quality oysters. In the present study, polymorphisms in the oyster cysteamine dioxygenase (CgADO) gene that encodes the central enzyme of the cysteamine pathway for taurine synthesis were investigated, and their association with taurine content was assessed in the Changhai (CH) and Qinhuangdao (QHD) populations. A total of 47 single nucleotide polymorphism (SNP) loci were identified in the exonic region of CgADO through Sanger sequencing, with a synonymous SNP (c.415T>C) showing a significant association with taurine content. Oysters with the CT genotype at c.415T>C exhibited higher taurine content than those with the TT genotype (p < 0.05). Moreover, a significant difference in the CgADO mRNA expression was observed between oysters with different genotypes, with higher expression in the CT genotype compared to the TT genotype (p < 0.001). These findings indicate the potential influence of CgADO polymorphisms on taurine content in C. gigas and provide candidate functional markers for the selective breeding of oyster varieties with improved taurine levels.