Ning Kong’s research while affiliated with Dalian Ocean University and other places

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.

The settlement of bivalve larvae is a complex process influenced by a combination of environmental, biological, and chemical factors, which is crucial for the development of the bivalve seedling industry. This study investigates the potential of glutamate (Glu) at various concentrations to induce settlement in Pacific oyster (Crassostrea gigas) mid-stage umbo larvae. The findings reveal that treating mid-stage umbo larvae with 10−4 M Glu for 6 h enhances growth and survival rates, significantly promotes the formation of eye spots, and accelerates settlement. Glu can effectively induce larval settlement, leading to the development of neural structures such as eye spots. This research confirms the efficacy of Glu as a larval settlement inducer in oysters, offering novel strategies for oyster seed production.

The Pacific oyster Crassostrea gigas is known to have an exceptional ability to accumulate zinc, which endows it with robust resistance to pathogens and makes it an excellent source of dietary zinc. ZIP1 has been identified as an important zinc uptake protein in other species, but its role in oysters remains unclear. In the present study, a ZIP1 homologue (CgZIP1-II) of the Zrt/Irt-like protein (ZIP) family was identified in C. gigas. The mRNA transcripts of CgZIP1-II were constitutively expressed in examined tissues of C. gigas, with higher levels in the hepatopancreas and gill. After zinc exposure, the mRNA transcripts of CgZIP1-II in the hepatopancreas showed a significant decline from 12 h to 14 d, while those in the gill significantly decreased at 72 h, followed by a recovery to basal level at 7 to 14 d. Immunocytochemical analysis revealed that the CgZIP1-II protein was mainly located at the plasma membrane of oyster hemocytes. Compared to the control cells, overexpression of CgZIP1-II in the transfected HEK293 cells resulted in a 2.44-fold (p < 0.05) increase in zinc content after incubation with 100 μM zinc for 24 h. Inhibition of endogenous CgZIP1-II expression with siRNAs led to a 42% reduction in zinc content in the hepatopancreas of oysters. Similarly, in vivo blocking of CgZIP1-II with anti-CgZIP1-II antibody caused a 43% decrease in zinc content in the hepatopancreas. These results collectively indicated that CgZIP1-II functioned as a zinc uptake transporter in C. gigas and played a certain role in zinc accumulation.

The Pacific oyster Crassostrea gigas is known to have an exceptional ability to accumulate zinc, which endows it with robust resistance to pathogens and makes it an excellent source of dietary zinc. ZIP1 has been identified as an important zinc uptake protein in other species, but its role in oysters remains unclear. In the present study, a ZIP1 homologue ( Cg ZIP1-II) of the Zrt/Irt-like protein (ZIP) family was identified in C . gigas . The mRNA transcripts of Cg ZIP1-II were constitutively expressed in examined tissues of C. gigas , with higher levels in the hepatopancreas and gill. After zinc exposure, the mRNA transcripts of Cg ZIP1-II in the hepatopancreas showed a significant decline from 12 h to 14 d, while those in the gill significantly decreased at 72 h, then followed by a recovery to basal levels at 7 d to 14 d. Immunocytochemical analysis revealed that the Cg ZIP1-II protein was mainly located at the plasma membrane of oyster haemocytes. Compared to the control cells, overexpression of Cg ZIP1-II in the transfected HEK293 cells resulted in a 2.44-fold ( p < 0.05) increase in zinc content after incubation with 100 µM zinc for 24 h. Inhibition of endogenous Cg ZIP1-II expression with siRNAs led to a 42% reduction in zinc content in the hepatopancreas of oysters. Similarly, in vivo blocking of Cg ZIP1-II with anti- Cg ZIP1-II antibody caused a 43% decrease in zinc content in the hepatopancreas. These results collectively indicated that Cg ZIP1-II functioned as a zinc uptake transporter in C. gigas and played an important role in zinc accumulation.

The Pacific oyster Crassostrea gigas, one of the most exploited molluscs in the world, has suffered from massive mortality in recent decades, and the occurrence mechanisms have not been well-characterized. In this study, to reveal the relationship of associated microbiota to the fitness of oysters, temporal dynamics of microbiota in the gill, hemolymph, and hepatopancreas of C. gigas during April 2018–January 2019 were investigated by 16S rRNA gene sequencing. The microbiota in C. gigas exhibited tissue heterogeneity, of which Spirochaetaceae was dominant in the gill and hemolymph while Mycoplasmataceae enriched in the hepatopancreas. Co-occurrence network demonstrated that the gill microbiota exhibited higher inter-taxon connectivity while the hemolymph microbiota had more modules. The richness (Chao1 index) and diversity (Shannon index) of microbial community in each tissue showed no significant seasonal variations, except for the hepatopancreas having a higher richness in the autumn. Similarly, beta diversity analysis indicated a relatively stable microbiota in each tissue during the sampling period, showing relative abundance of the dominant taxa exhibiting temporal dynamics. Results indicate that the microbial community in C. gigas showed a tissue-specific stability with temporal dynamics in the composition, which might be essential for the tissue functioning and environmental adaption in oysters. This work provides a baseline microbiota in C. gigas and is helpful for the understanding of host-microbiota interaction in oysters.