Effects of the dinoflagellate Alexandrium minutum and its toxin (saxitoxin) on the functional activity and gene expression of Crassostrea gigas hemocytes |
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| Affiliation: | 1. Laboratory of Immunology Applied to Aquaculture, Department of Cell Biology, Embryology and Genetics, Biological Sciences Center, Federal University of Santa Catarina, 88040-900 Florianópolis, SC, Brazil;2. Laboratory of Immunology and Pathology of Invertebrates, Department of Molecular Biology, Exact and Natural Sciences Center, Federal University of Paraíba – Campus I, 58051-900 João Pessoa, PB, Brazil;3. LEMAR CNRS UMR 6539, Université de Bretagne Occidentale, IUEM, 29280 Plouzané, France;1. Laboratoire des Sciences de l’Environnement Marin (LEMAR), Institut Universitaire Européen de la Mer (IUEM), UBO/CNRS, rue Dumont d’Urville, technopôle Brest-Iroise, 29280 Plouzané, France;2. Laboratoire Phycotoxines, Ifremer, Institut Français de Recherche pour l’Exploitation de la Mer, BP 21105, 44311 Nantes CEDEX3, France;3. Laboratoire Milieu Marin, INSTM, Institut National des Sciences et Technologies de la Mer, 28 rue du 2 mars 1934, 2025 Salammbô, Tunisie;4. Laboratory of Immunology and Pathology of Invertebrates, Department of Molecular Biology, Exact and Natural Sciences Center, Federal University of Paraíba—Campus I, 58051-900 João Pessoa, PB, Brazil;5. Université de Bordeaux UMR 5805 EPOC, station marine d’Arcachon, 2 rue du Pr Jolyet, 33120 Arcachon, France;1. Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;1. Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;2. Liaoning Key Laboratory of Marine Animal Immunology and Disease Control, Dalian Ocean University, Dalian 116023, China;3. University of Chinese Academy of Sciences, Beijing 100049, China;1. Université de Bretagne Occidentale (UBO), UMR 6539 LEMAR, IUEM, Technopôle Brest-Iroise, Rue Dumont d''Urville, 29280 Plouzané, France;2. Ifremer, UMR 6539 LEMAR, 11 presqu''île du Vivier, 29840 Argenton-en-Landunvez, France;1. Liaoning Key Laboratory of Marine Animal Immunology, Dalian Ocean University, Dalian, 116023, China;2. Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai, 519000, China;3. Functional Laboratory of Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266235, China;4. Liaoning Key Laboratory of Marine Animal Immunology and Disease Control, Dalian Ocean University, Dalian, 116023, China;5. Dalian Key Laboratory of Aquatic Animal Disease Prevention and Control, Dalian Ocean University, Dalian, 116023, China |
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| Abstract: | Blood cells or hemocytes are the major component of the cellular immune responses in bivalves. Recent evidences have demonstrated that the immune functions of these cells can be impaired by harmful algae and their toxins. In this study, we compared the in vitro effect of the toxic dinoflagellate Alexandrium minutum and its purified paralytic toxin, saxitoxin (STX) on the oyster Crassostrea gigas hemocytes. Oyster hemocytes were incubated with A. minutum or STX, and their size, complexity, viability, phagocytic activity and reactive oxygen species (ROS) production were analyzed through flow cytometry. Also, expression of eleven defense-related genes was evaluated through real-time quantitative PCR. Cell incubation with both, the noxious microalga and STX did not alter hemocyte viability neither complexity. However, their phagocytic capacity and ROS production were significantly affected by both treatments. On the other hand, only A. minutum exposure resulted in increase of hemocyte size. Transcript levels of the gene encoding the cytokine Interleukin-17 was significantly higher (4.5-fold) after hemocytes were exposed to A. minutum, which contrasted with a decreased (7-fold) number of transcripts, when hemocytes were treated with STX. The purified toxin also led to lower transcript levels of a cytochrome P450 gene, the CYP356A1 (3.5-fold). On the other hand, hemocytes incubated with STX presented higher mRNA levels of antimicrobial peptide defensin-2 (7-fold) and heat shock protein Hsp70 (2-fold) genes. Altogether, these results suggest that the noxious alga A. minutum and STX can indeed negatively affect immunocompetence of C. gigas hemocytes, although in distinct manners. These differences could be due to a lower STX bioavailability in living microalgal cultures or alternatively to the presence of allelopathic compounds produced by living microalgae. This is the first report comparing the transcription of defense-related genes in oysters exposed to a harmful alga and its purified toxin. |
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| Keywords: | Flow cytometry Gene expression Harmful algae Hemocytes Saxitoxin |
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