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Chen Z, Wang X, Yu G, Pu J, Li X, Tao Z, Duan Z, Zhang F, Han P, Li H, Yu H. Genome-wide identification, characterization, molecular evolution and expression profiling analysis of scavenger receptors in black rockfish (Sebastes schlegelii). FISH & SHELLFISH IMMUNOLOGY 2024; 151:109686. [PMID: 38852787 DOI: 10.1016/j.fsi.2024.109686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2024] [Revised: 05/24/2024] [Accepted: 06/07/2024] [Indexed: 06/11/2024]
Abstract
The scavenger receptors (SRs) gene family is considered as the membrane-associated pattern recognition receptors that plays important roles in the immune responses of organisms. However, there is currently limited research on the systematic identification of the SRs gene family in teleost and their role in the innate immunity of S. schegelii. In this study, we identified and annotated 15 SRs genes in S. schegelii. Through phylogenetic analysis, analysis of conserved domains, gene structure, and motif composition, we found that SRs gene family within different classes were relatively conserved. Additionally, we used qRT-PCR to analyze the expression patterns of SRs genes in immune-related tissues from healthy and Acinetobacter johnsonii-infected S. schegelii. The results showed that SRs genes exhibited different tissue expression patterns and the expression of SRs genes significantly changed after A. johnsonii infection. These results provided a valuable basis for further understanding of the functions of SRs in the innate immune response of S. schegelii.
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Affiliation(s)
- Zhentao Chen
- Key Laboratory of Marine Genetics and Breeding, Ministry of Education, Ocean University of China, 266003, Qingdao, Shandong, China
| | - Xuangang Wang
- Key Laboratory of Marine Genetics and Breeding, Ministry of Education, Ocean University of China, 266003, Qingdao, Shandong, China
| | - Gan Yu
- Key Laboratory of Marine Genetics and Breeding, Ministry of Education, Ocean University of China, 266003, Qingdao, Shandong, China
| | - Jingrun Pu
- Key Laboratory of Marine Genetics and Breeding, Ministry of Education, Ocean University of China, 266003, Qingdao, Shandong, China
| | - Xuechen Li
- Key Laboratory of Marine Genetics and Breeding, Ministry of Education, Ocean University of China, 266003, Qingdao, Shandong, China
| | - Ze Tao
- Key Laboratory of Marine Genetics and Breeding, Ministry of Education, Ocean University of China, 266003, Qingdao, Shandong, China
| | - Zhixiang Duan
- Key Laboratory of Marine Genetics and Breeding, Ministry of Education, Ocean University of China, 266003, Qingdao, Shandong, China
| | - Fan Zhang
- Key Laboratory of Marine Genetics and Breeding, Ministry of Education, Ocean University of China, 266003, Qingdao, Shandong, China
| | - Ping Han
- Key Laboratory of Marine Genetics and Breeding, Ministry of Education, Ocean University of China, 266003, Qingdao, Shandong, China
| | - Hengshun Li
- Key Laboratory of Marine Genetics and Breeding, Ministry of Education, Ocean University of China, 266003, Qingdao, Shandong, China
| | - Haiyang Yu
- Key Laboratory of Marine Genetics and Breeding, Ministry of Education, Ocean University of China, 266003, Qingdao, Shandong, China.
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Jin C, Wang M, Gao X, Wu S, Ding H, Bao Z, Wang B, Hu J. Deciphering scavenger receptors reveals key regulators in the intestine that function in carotenoid coloration of leopard coral groupers (Plectropomus leopardus). Int J Biol Macromol 2024; 260:129387. [PMID: 38253150 DOI: 10.1016/j.ijbiomac.2024.129387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 12/16/2023] [Accepted: 01/03/2024] [Indexed: 01/24/2024]
Abstract
Carotenoid based body coloration are common features in fish, which depends on the diet derived carotenoids pigments deposition, employing a bunch of carotenoid uptake, absorption and processing related genes. Scavenger receptors are a large family of cell surface receptors with complex structure and diverse functions. However, the SRs genes have been insufficiently explored concerning their role in fish carotenoid coloration. Here, we systemically identified 19 SRs family genes and investigated their expression patterns of in various tissues of P. leopardus. Expression analysis unveiled the diverse involvements of SRs in the intestine of P. leopardus with different body colors and the responses to exogenous carotenoids. Notably, cd36, emerged as a pivotal factor in intestinal functions predominantly localized in the intestinal epithelial and goblet cells. Knockdown of cd36 led to the reduction in skin brightness and carotenoid levels in both intestine and skin, while overexpressing cd36 increased the carotenoids uptake of cells in vitro. Additionally, our investigations revealed that cd36 exerts regulation on genes associated with carotenoid uptake, transport, and processing. To sum up, our results provide a comprehensive view on SRs functions in carotenoid coloration of P. leopardus and will facilitate the understanding on the mechanism of carotenoids coloration of vertebrates.
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Affiliation(s)
- Chaofan Jin
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences/Key Laboratory of Tropical Aquatic Germplasm of Hainan Province, Sanya Oceanographic Institution, Ocean University of China, Qingdao/Sanya, China
| | - Mengya Wang
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences/Key Laboratory of Tropical Aquatic Germplasm of Hainan Province, Sanya Oceanographic Institution, Ocean University of China, Qingdao/Sanya, China
| | - Xin Gao
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences/Key Laboratory of Tropical Aquatic Germplasm of Hainan Province, Sanya Oceanographic Institution, Ocean University of China, Qingdao/Sanya, China
| | - Shaoxuan Wu
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences/Key Laboratory of Tropical Aquatic Germplasm of Hainan Province, Sanya Oceanographic Institution, Ocean University of China, Qingdao/Sanya, China
| | - Hui Ding
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences/Key Laboratory of Tropical Aquatic Germplasm of Hainan Province, Sanya Oceanographic Institution, Ocean University of China, Qingdao/Sanya, China
| | - Zhenmin Bao
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences/Key Laboratory of Tropical Aquatic Germplasm of Hainan Province, Sanya Oceanographic Institution, Ocean University of China, Qingdao/Sanya, China; Hainan Seed Industry Laboratory, Sanya 572025, China; Southern Marine Science and Engineer Guangdong Laboratory, Guangzhou 511458, China
| | - Bo Wang
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences/Key Laboratory of Tropical Aquatic Germplasm of Hainan Province, Sanya Oceanographic Institution, Ocean University of China, Qingdao/Sanya, China; Hainan Seed Industry Laboratory, Sanya 572025, China.
| | - Jingjie Hu
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences/Key Laboratory of Tropical Aquatic Germplasm of Hainan Province, Sanya Oceanographic Institution, Ocean University of China, Qingdao/Sanya, China; Hainan Seed Industry Laboratory, Sanya 572025, China; Southern Marine Science and Engineer Guangdong Laboratory, Guangzhou 511458, China.
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Wang M, Wu S, Ding H, Wang M, Ma J, Xiao J, Wang B, Bao Z, Hu J. Dietary antarctic krill improves antioxidant capacity, immunity and reduces lipid accumulation, insights from physiological and transcriptomic analysis of Plectropomus leopardus. BMC Genomics 2024; 25:210. [PMID: 38408914 PMCID: PMC10895837 DOI: 10.1186/s12864-024-10099-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 02/08/2024] [Indexed: 02/28/2024] Open
Abstract
BACKGROUND Due to its enormous biomass, Antarctic krill (Euphausia superba) plays a crucial role in the Antarctic Ocean ecosystem. In recent years, Antarctic krill has found extensive application in aquaculture, emerging as a sustainable source of aquafeed with ideal nutritional profiles. However, a comprehensive study focused on the detailed effects of dietary Antarctic krill on aquaculture animals, especially farmed marine fishes, is yet to be demonstrated. RESULTS In this study, a comparative experiment was performed using juvenile P. leopardus, fed with diets supplemented with Antarctic krill (the krill group) or without Antarctic krill (the control group). Histological observation revealed that dietary Antarctic krill could reduce lipid accumulation in the liver while the intestine exhibited no obvious changes. Enzyme activity measurements demonstrated that dietary Antarctic krill had an inhibitory effect on oxidative stress in both the intestine and the liver. By comparative transcriptome analysis, a total of 1,597 and 1,161 differentially expressed genes (DEGs) were identified in the intestine and liver, respectively. Functional analysis of the DEGs showed multiple enriched terms significantly related to cholesterol metabolism, antioxidants, and immunity. Furthermore, the expression profiles of representative DEGs, such as dhcr7, apoa4, sc5d, and scarf1, were validated by qRT-PCR and fluorescence in situ hybridization. Finally, a comparative transcriptome analysis was performed to demonstrate the biased effects of dietary Antarctic krill and astaxanthin on the liver of P. leopardus. CONCLUSIONS Our study demonstrated that dietary Antarctic krill could reduce lipid accumulation in the liver of P. leopardus, enhance antioxidant capacities in both the intestine and liver, and exhibit molecular-level improvements in lipid metabolism, immunity, and antioxidants. It will contribute to understanding the protective effects of Antarctic krill in P. leopardus and provide insights into aquaculture nutritional strategies.
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Affiliation(s)
- Mengya Wang
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences/Key Laboratory of Tropical Aquatic Germplasm of Hainan Province, Sanya Oceanographic Institution, Ocean University of China, Qingdao, Sanya, China
| | - Shaoxuan Wu
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences/Key Laboratory of Tropical Aquatic Germplasm of Hainan Province, Sanya Oceanographic Institution, Ocean University of China, Qingdao, Sanya, China
| | - Hui Ding
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences/Key Laboratory of Tropical Aquatic Germplasm of Hainan Province, Sanya Oceanographic Institution, Ocean University of China, Qingdao, Sanya, China
| | - Mingyi Wang
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences/Key Laboratory of Tropical Aquatic Germplasm of Hainan Province, Sanya Oceanographic Institution, Ocean University of China, Qingdao, Sanya, China
| | - Jiayi Ma
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences/Key Laboratory of Tropical Aquatic Germplasm of Hainan Province, Sanya Oceanographic Institution, Ocean University of China, Qingdao, Sanya, China
| | - Jie Xiao
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences/Key Laboratory of Tropical Aquatic Germplasm of Hainan Province, Sanya Oceanographic Institution, Ocean University of China, Qingdao, Sanya, China
| | - Bo Wang
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences/Key Laboratory of Tropical Aquatic Germplasm of Hainan Province, Sanya Oceanographic Institution, Ocean University of China, Qingdao, Sanya, China.
- Hainan Yazhou Bay Seed Laboratory, 572025, Sanya, China.
| | - Zhenmin Bao
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences/Key Laboratory of Tropical Aquatic Germplasm of Hainan Province, Sanya Oceanographic Institution, Ocean University of China, Qingdao, Sanya, China
- Hainan Yazhou Bay Seed Laboratory, 572025, Sanya, China
| | - Jingjie Hu
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences/Key Laboratory of Tropical Aquatic Germplasm of Hainan Province, Sanya Oceanographic Institution, Ocean University of China, Qingdao, Sanya, China
- Hainan Yazhou Bay Seed Laboratory, 572025, Sanya, China
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Sun X, Bao N, Rui C, Xue Y, Fang Q, Zheng T, Lin Z, Liu X, Wang X. Identification of large yellow croakers (Larimichthys crocea) scavenger receptor genes: Involvement in immune response to Pseudomonas plecoglossicida infection and hypoxia-exposure experiments. FISH & SHELLFISH IMMUNOLOGY 2024; 144:109307. [PMID: 38122953 DOI: 10.1016/j.fsi.2023.109307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 12/13/2023] [Accepted: 12/14/2023] [Indexed: 12/23/2023]
Abstract
Scavenger receptors (SRs) are pattern recognition receptors involved in the innate immune defense against pathogen infection in fish. However, there has not been much research done on teleosts. In this study, 18 members of the SR gene family were found in large yellow croaker. The identification of the SR gene family showed that the protein length of SR members in large yellow croaker were quite different, and most SR genes were distributed in nuclear and endoplasmic. The evolutionary relationship, exon/intron structure and motif analysis revealed that members of the SR gene family were highly conserved. The results of the expression profiles after Pseudomonas plecoglossicida infection and hypoxia-exposure demonstrated that SR members were involved in inflammatory reactions. Especially, COLEC12 and SCARF1 exhibited substantial changes in response to both P. plecoglossicida and hypoxia stress, indicating their possible immunological functions. The result of this study revealed that SR genes played a vital part in the innate immune response of large yellow croaker, and would give important details for a deeper comprehension of the SR gene family's regulation mechanism under various conditions in large yellow croaker.
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Affiliation(s)
- Xuanyang Sun
- Key Laboratory of Aquacultural Biotechnology (Ningbo University), Ministry of Education, Ningbo, Zhejiang, China.
| | - Ning Bao
- Key Laboratory of Aquacultural Biotechnology (Ningbo University), Ministry of Education, Ningbo, Zhejiang, China.
| | - Chen Rui
- Key Laboratory of Aquacultural Biotechnology (Ningbo University), Ministry of Education, Ningbo, Zhejiang, China.
| | - Yadong Xue
- Key Laboratory of Aquacultural Biotechnology (Ningbo University), Ministry of Education, Ningbo, Zhejiang, China.
| | - Qian Fang
- Key Laboratory of Aquacultural Biotechnology (Ningbo University), Ministry of Education, Ningbo, Zhejiang, China.
| | - Tianyu Zheng
- Key Laboratory of Aquacultural Biotechnology (Ningbo University), Ministry of Education, Ningbo, Zhejiang, China.
| | - Ziyang Lin
- Key Laboratory of Aquacultural Biotechnology (Ningbo University), Ministry of Education, Ningbo, Zhejiang, China.
| | - Xiumei Liu
- College of Life Sciences, Yantai University, Yantai, China.
| | - Xubo Wang
- Key Laboratory of Aquacultural Biotechnology (Ningbo University), Ministry of Education, Ningbo, Zhejiang, China; National Engineering Research Laboratory of marine Biotechnology and Engineering, Ningbo University, Ningbo, Zhejiang, China; Collaborative Innovation Center for Zhejiang Marine High-efficiency and Healthy Aquaculture, Ningbo University, Ningbo, Zhejiang, China; Key Laboratory of Green Mariculture (Co-construction By Ministry and Province), Ministry of Agriculture and Rural, Ningbo University, China.
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Goh KW, Abdul Kari Z, Wee W, Zakaria NNA, Rahman MM, Kabir MA, Abdul Hamid NK, Tahiluddin AB, Kamarudin AS, Téllez–Isaías G, Wei LS. Exploring the roles of phytobiotics in relieving the impacts of Edwardsiella tarda infection on fish: a mini-review. Front Vet Sci 2023; 10:1149514. [PMID: 37476823 PMCID: PMC10355809 DOI: 10.3389/fvets.2023.1149514] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2023] [Accepted: 06/15/2023] [Indexed: 07/22/2023] Open
Abstract
Edwardsiellosis caused by Edwardsiella tarda resulted in significant economic losses in aquaculture operations worldwide. This disease could infect a wide range of hosts, including freshwater, brackish water, and marine aquatic animals. Currently, antibiotics and vaccines are being used as prophylactic agents to overcome Edwardsiellosis in aquaculture. However, application of antibiotics has led to antibiotic resistance among pathogenic bacteria, and the antibiotic residues pose a threat to public health. Meanwhile, the use of vaccines to combat Edwardsiellosis requires intensive labor work and high costs. Thus, phytobiotics were attempted to be used as antimicrobial agents to minimize the impact of Edwardsiellosis in aquaculture. These phytobiotics may also provide farmers with new options to manage aquaculture species' health. The impact of Edwardsiellosis in aquaculture worldwide was elaborated on and highlighted in this review study, as well as the recent application of phytobiotics in aquaculture and the status of vaccines to combat Edwardsiellosis. This review also focuses on the potential of phytobiotics in improving aquatic animal growth performance, enhancing immune system function, and stimulating disease resistance.
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Affiliation(s)
- Khang Wen Goh
- Faculty of Data Science and Information Technology, INTI International University, Nilai, Malaysia
| | - Zulhisyam Abdul Kari
- Department of Agricultural Science, Faculty of Agro-Based Industry, Universiti Malaysia Kelantan, Jeli, Kelantan, Malaysia
- Advanced Livestock and Aquaculture Research Group, Faculty of Agro-Based Industry, Universiti Malaysia Kelantan, Jeli, Kelantan, Malaysia
| | - Wendy Wee
- Center of Fundamental and Continuing Education, Universiti Malaysia Terengganu, Kuala Nerus, Terengganu, Malaysia
| | - Nik Nur Azwanida Zakaria
- Advanced Livestock and Aquaculture Research Group, Faculty of Agro-Based Industry, Universiti Malaysia Kelantan, Jeli, Kelantan, Malaysia
- Department of Agro-Based Industry, Faculty of Agro-Based Industry, Universiti Malaysia Kelantan, Jeli, Kelantan, Malaysia
| | - Mohammad Mijanur Rahman
- Department of Agricultural Science, Faculty of Agro-Based Industry, Universiti Malaysia Kelantan, Jeli, Kelantan, Malaysia
- Advanced Livestock and Aquaculture Research Group, Faculty of Agro-Based Industry, Universiti Malaysia Kelantan, Jeli, Kelantan, Malaysia
| | | | | | - Albaris B. Tahiluddin
- College of Fisheries, Mindanao State University-Tawi-Tawi College of Technology and Oceanography, Bongao, Tawi-Tawi, Philippines
| | - Ahmad Syazni Kamarudin
- School of Animal Science, Aquatic Science and Environment, Faculty of Bioresources and Food Industry, Universiti Sultan Zainal Abidin (UniSZA), Besut Campus, Besut, Terengganu, Malaysia
| | | | - Lee Seong Wei
- Department of Agricultural Science, Faculty of Agro-Based Industry, Universiti Malaysia Kelantan, Jeli, Kelantan, Malaysia
- Advanced Livestock and Aquaculture Research Group, Faculty of Agro-Based Industry, Universiti Malaysia Kelantan, Jeli, Kelantan, Malaysia
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Chen J, Han P, Liu X, Wang X. Characterization of Japanese flounder (Paralichthys olivaceus) STAT members: An immune-related gene family involved in Edwardsiella tarda and temperature stress. FISH & SHELLFISH IMMUNOLOGY 2023; 138:108818. [PMID: 37201733 DOI: 10.1016/j.fsi.2023.108818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2023] [Revised: 05/13/2023] [Accepted: 05/15/2023] [Indexed: 05/20/2023]
Abstract
The signal transducer and activator of transcription (STAT) family members are not only the transcriptional activators, but also play important roles in regulating inflammatory response. Some members have been reported to be involved in innate bacterial and antiviral immunity in aquatic organisms. However, no systematic research on STATs has been found in teleost. In this present study, we characterized six STAT genes in Japanese flounder based on bioinformatics methods, namely PoSTAT1, PoSTAT2, PoSTAT3, PoSTAT4, PoSTAT5 and PoSTAT6. The phylogenetic analysis of STATs in fish indicated that STATs were highly conserved and revealed an absence of STAT5 in a few species. Further analysis of gene structures and motifs showed STAT proteins shared a similar structure and probably had similar functionality in Japanese flounder. The expression profiles of different development stages and tissues demonstrated that PoSTATs exhibited specificity in temporality and spatiality as well as PoSTAT4 was highly expressed in gill. The transcriptome data analysis of E. tarda and temperature stress showed that PoSTAT1 and PoSTAT2 were more respective to these two kinds of stress. In addition, the results also demonstrated that these PoSTATs might regulate immune response in different ways, manifested by up-regulation in E. tarda infection and down-regulation in temperature stress. In a word, this systematic analysis of PoSTATs would provide valuable information about the phylogenetic relationship of STATs in fish species and help understand the role of STAT genes in the immune response of Japanese flounder.
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Affiliation(s)
- Jianming Chen
- Key Laboratory of Aquacultural Biotechnology (Ningbo University), Ministry of Education, Ningbo, Zhejiang, China.
| | - Ping Han
- Key Laboratory of Aquacultural Biotechnology (Ningbo University), Ministry of Education, Ningbo, Zhejiang, China; Key Laboratory of Marine Genetics and Breeding, Ministry of Education, Ocean University of China, Qingdao, Shandong, China.
| | - Xiumei Liu
- College of Life Sciences, Yantai University, Yantai, China.
| | - Xubo Wang
- Key Laboratory of Aquacultural Biotechnology (Ningbo University), Ministry of Education, Ningbo, Zhejiang, China; National Engineering Research Laboratory of Marine Biotechnology and Engineering, Ningbo University, China; Collaborative Innovation Center for Zhejiang Marine High-efficiency and Healthy Aquaculture, Ningbo University, China; Key Laboratory of Marine Biotechnology of Zhejiang Province, Ningbo University, Ningbo, China.
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Molecular Characterization, Expression, Evolutionary Selection, and Biological Activity Analysis of CD68 Gene from Megalobrama amblycephala. Int J Mol Sci 2022; 23:ijms232113133. [PMID: 36361921 PMCID: PMC9656401 DOI: 10.3390/ijms232113133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 10/21/2022] [Accepted: 10/24/2022] [Indexed: 11/24/2022] Open
Abstract
CD68 is a highly glycosylated transmembrane glycoprotein that belongs to the lysosome-associated membrane glycoprotein family and is involved in various immune processes. In this study, Megalobrama amblycephala CD68 (MaCD68) was cloned and characterized, and its expression patterns and evolutionary characteristics were analyzed. The coding region of MaCD68 was 987 bp, encoding 328 amino acids, and the predicted protein molecular weight was 34.9 kDa. MaCD68 contained two transmembrane helical structures and 18 predicted N-glycosylation sites. Multiple sequence alignments showed that the MaCD68 protein had high homology with other fish, and their functional sites were also highly conserved. Phylogenetic analysis revealed that MaCD68 and other cypriniformes fish clustered into one branch. Adaptive evolution analysis identified several positively selected sites of teleost CD68 using site and branch-site models, indicating that it was under positive selection pressure during evolution. Quantitative real-time reverse transcription polymerase chain reaction analysis showed that MaCD68 was highly expressed in the head kidney, spleen, and heart. After Aeromonas hydrophila infection, MaCD68 was significantly upregulated in all tested tissues, peaking at 12 h post-infection (hpi) in the kidney and head kidney and at 120 hpi in the liver and spleen, suggesting that MaCD68 participated in the innate immune response of the host against bacterial infection. Immunohistochemical and immunofluorescence analyses also showed that positive signals derived from the MaCD68 protein were further enhanced after bacterial and lipopolysaccharide treatment, which suggested that MaCD68 is involved in the immune response and could be used as a macrophage marker. Biological activity analysis indicated that recombinant MaCD68 (rMaCD68) protein had no agglutination or bactericidal effects on A. hydrophila but did have these effects on Escherichia coli. In conclusion, these results suggest that MaCD68 plays a vital role in the immune response against pathogens, which is helpful in understanding the immune responses and mechanisms of M. amblycephala.
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