Fish Shellfish Immunol 2022 Jul 30;128:82-90. Epub 2022 Jul 30.
Liaoning Key Laboratory of Marine Animal Immunology, Dalian Ocean University, Dalian, 116023, China; Southern Laboratory of Ocean Science and Engineering (Guangdong, Zhuhai), Zhuhai, 519000, China; Functional Laboratory of Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266235, China; Liaoning Key Laboratory of Marine Animal Immunology and Disease Control, Dalian Ocean University, Dalian, 116023, China; Dalian Key Laboratory of Aquatic Animal Disease Prevention and Control, Dalian Ocean University, Dalian, 116023, China. Electronic address:
The stimulator of interferon gene (STING), an intracellular sensor of cyclic dinucleotides, is critical to the innate immune response, especially the induction of type I interferon (IFN) during pathogenic infection. A STING homologue (CgSTING) regulating the expression of IFN-like protein (CgIFNLP) was previously identified in the Pacific oyster Crassostrea gigas, and its involvement in antibacterial immunity was further investigated in the present study. The mRNA transcripts of CgSTING were ubiquitously detected in all the three subpopulations of haemocytes with the highest expression in semi-granulocytes. After the stimulation with Vibrio splendidus, the mRNA expression of CgSTING in haemocytes was significantly up-regulated and peaked at 72 h, which was 12.91-fold of that in control group (p < 0.01). The CgSTING protein was mainly located in the cytoplasm of haemocytes. After the expression of CgSTING was knocked down (0.12-fold of that in control group, p < 0.05) by RNAi, the mRNA expression levels of interleukin17-1 (CgIL17-1), interleukin17-3 (CgIL17-3), interleukin17-4 (CgIL17-4), defensins (Cgdefh1, Cgdefh2), big defensin (CgBigDef1), interferon-like protein (CgIFNLP), tumor necrosis factor (CgTNF) and nuclear factor-κB (CgRel) all decreased significantly at 12 h after V. splendidus stimulation, which was 0.12-fold-0.72-fold (p < 0.05) of that in control group, respectively. The positive signals of CgRel were observed in the haemocyte nucleus after V. splendidus stimulation. The nuclear translocation of CgRel was suppressed in CgSTING-RNAi oysters, and the green signals of CgRel were mainly observed in the haemocyte cytoplasm after V. splendidus stimulation. Furthermore, the number of V. splendidus in the haemolymph of CgSTING-RNAi oysters increased significantly, which was 26.78-fold (p < 0.01) of that in the control group at 12 h after V. splendidus stimulation. These results indicated that CgSTING played important role in the immune defense against bacterial infection by inducing the expressions of cytokines and defensins.