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Midtbø HMD, Eichner C, Hamre LA, Dondrup M, Flesland L, Tysseland KH, Kongshaug H, Borchel A, Skoge RH, Nilsen F, Øvergård AC. Salmon louse labial gland enzymes: implications for host settlement and immune modulation. Front Genet 2024; 14:1303898. [PMID: 38299097 PMCID: PMC10828956 DOI: 10.3389/fgene.2023.1303898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Accepted: 12/18/2023] [Indexed: 02/02/2024] Open
Abstract
Salmon louse (Lepeophtheirus salmonis) is a skin- and blood-feeding ectoparasite, infesting salmonids. While feeding, labial gland proteins from the salmon louse may be deposited on the Atlantic salmon (Salmo salar) skin. Previously characterized labial gland proteins are involved in anti-coagulation and may contribute to inhibiting Atlantic salmon from mounting a sufficient immune response against the ectoparasite. As labial gland proteins seem to be important in the host-parasite interaction, we have, therefore, identified and characterized ten enzymes localized to the labial gland. They are a large group of astacins named L. salmonis labial gland astacin 1-8 (LsLGA 1-8), one serine protease named L. salmonis labial gland serine protease 1 (LsLGSP1), and one apyrase named L. salmonis labial gland apyrase 1 (LsLGAp1). Protein domain predictions showed that LsLGA proteins all have N-terminal ShK domains, which may bind to potassium channels targeting the astacins to its substrate. LsLGA1 and -4 are, in addition, expressed in another gland type, whose secrete also meets the host-parasite interface. This suggests that LsLGA proteins may have an anti-microbial function and may prevent secondary infections in the wounds. LsLGAp1 is predicted to hydrolyze ATP or AMP and is, thereby, suggested to have an immune dampening function. In a knockdown study targeting LsLGSP1, a significant increase in IL-8 and MMP13 at the skin infestation site was seen under LsLGSP1 knockdown salmon louse compared to the control, suggesting that LsLGSP1 may have an anti-inflammatory effect. Moreover, most of the identified labial gland proteins are expressed in mature copepodids prior to host settlement, are not regulated by starvation, and are expressed at similar or higher levels in lice infesting the salmon louse-resistant pink salmon (Oncorhynchus gorbuscha). This study, thereby, emphasizes the importance of labial gland proteins for host settlement and their immune dampening function. This work can further contribute to anti-salmon louse treatment such as vaccine development, functional feed, or gene-edited salmon louse-resistant Atlantic salmon.
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Affiliation(s)
| | - Christiane Eichner
- Sea Lice Research Centre, Department of Biological Sciences, University of Bergen, Bergen, Norway
| | - Lars Are Hamre
- Sea Lice Research Centre, Department of Biological Sciences, University of Bergen, Bergen, Norway
| | - Michael Dondrup
- Sea Lice Research Centre, Department of Informatics, University of Bergen, Bergen, Norway
| | - Linn Flesland
- Sea Lice Research Centre, Department of Biological Sciences, University of Bergen, Bergen, Norway
| | | | - Heidi Kongshaug
- Sea Lice Research Centre, Department of Biological Sciences, University of Bergen, Bergen, Norway
| | - Andreas Borchel
- Sea Lice Research Centre, Department of Biological Sciences, University of Bergen, Bergen, Norway
| | - Renate Hvidsten Skoge
- Sea Lice Research Centre, Department of Biological Sciences, University of Bergen, Bergen, Norway
| | - Frank Nilsen
- Sea Lice Research Centre, Department of Biological Sciences, University of Bergen, Bergen, Norway
| | - Aina-Cathrine Øvergård
- Sea Lice Research Centre, Department of Biological Sciences, University of Bergen, Bergen, Norway
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Gislefoss E, Abdelrahim Gamil AA, Øvergård AC, Evensen Ø. Identification and characterization of two salmon louse heme peroxidases and their potential as vaccine antigens. iScience 2023; 26:107991. [PMID: 37854698 PMCID: PMC10579435 DOI: 10.1016/j.isci.2023.107991] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2023] [Revised: 07/09/2023] [Accepted: 09/16/2023] [Indexed: 10/20/2023] Open
Abstract
Salmon louse, Lepeophtheirus salmonis, represents major challenge for salmon farming. Current treatments impose welfare issues and are costly, whereas prophylactic measures are unavailable. Two salmon louse heme peroxidases (LsPxtl-1 and LsPxtl-2) were tested for their importance for parasite development and as potential vaccine candidates. LsPxtl-1 possesses two heme peroxidase domains and is expressed in ovaries and gut, whereas LsPxtl-2 encodes one domain and contains N-terminal signal peptide and an Eph receptor ligand-binding domain. LsPxtl-1, but not LsPxtl-2, knockdown in nauplius II stage caused poor swimming and death, indicating its importance for parasite development. Immunizations using single DNA plasmid injection encoding the peroxidases or heterologous prime (DNA) and boost (recombinant LsPxtl-2 protein) gave non-significant reduction in lice numbers. Single injection gave low specific antibody levels compared with the prime-boost. The findings suggest LsPxtl-1 is important for parasite development but formulations and vaccination modalities used did not significantly reduce lice infestation.
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Affiliation(s)
- Elisabeth Gislefoss
- Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway
- Sea Lice Research Center, University of Bergen, Bergen, Norway
| | - Amr Ahmed Abdelrahim Gamil
- Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway
- Sea Lice Research Center, University of Bergen, Bergen, Norway
| | - Aina-Cathrine Øvergård
- Department of Biological Sciences, University of Bergen, Bergen, Norway
- Sea Lice Research Center, University of Bergen, Bergen, Norway
| | - Øystein Evensen
- Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway
- Sea Lice Research Center, University of Bergen, Bergen, Norway
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Borchel A, Eichner C, Øvergård AC. Mining Lepeophtheirus salmonis RNA-Seq data for qPCR reference genes and their application in Caligus elongatus. Exp Parasitol 2023; 248:108511. [PMID: 36921884 DOI: 10.1016/j.exppara.2023.108511] [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: 01/30/2023] [Revised: 03/10/2023] [Accepted: 03/11/2023] [Indexed: 03/14/2023]
Abstract
Lepeophtheirus salmonis and Caligus elongatus are two parasitic copepod species posing a significant threat to salmonid aquaculture. Consequently, several gene expression studies are executed each year to gain new knowledge and treatment strategies. Though, to enable accurate gene expression measurements by quantitative real time PCR, stable reference genes are needed. Previous studies have mainly focused on a few genes selected based on their function as housekeeping genes, as these are often stably expressed in various cells and tissues. In the present study, however, RNA-sequencing data from 127 L. salmonis samples from different life stages and diverse environmental conditions were used to identify new candidate reference genes displaying low variation. From this, six genes were selected, and the stability validated by qPCR on samples from different life stages. Since neither a genome nor comprehensive RNA sequencing data are available for C. elongatus, homologous genes to those identified for L. salmonis were identified within a C. elongatus transcriptome assembly and validated by qPCR in different life stages. Overall, the genes eukaryotic translation initiation factor 1A (EIF1A) and serine/threonine-protein phosphatase 1 (PP1) displayed the highest stability in L. salmonis, while the combination of PP1 and ribosomal protein S13 (RPS13) was found to have the highest stability in C. elongatus. These genes are well-suited reference genes for qPCR applications which allow for accurate normalization of target genes.
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Affiliation(s)
- Andreas Borchel
- University of Bergen, SLRC-Sea Lice Research Centre, Department of Biological Sciences, Pb. 7803, 5020, Bergen, Norway.
| | - Christiane Eichner
- University of Bergen, SLRC-Sea Lice Research Centre, Department of Biological Sciences, Pb. 7803, 5020, Bergen, Norway
| | - Aina-Cathrine Øvergård
- University of Bergen, SLRC-Sea Lice Research Centre, Department of Biological Sciences, Pb. 7803, 5020, Bergen, Norway
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Skern-Mauritzen R, Malde K, Eichner C, Dondrup M, Furmanek T, Besnier F, Komisarczuk AZ, Nuhn M, Dalvin S, Edvardsen RB, Klages S, Huettel B, Stueber K, Grotmol S, Karlsbakk E, Kersey P, Leong JS, Glover KA, Reinhardt R, Lien S, Jonassen I, Koop BF, Nilsen F. The salmon louse genome: Copepod features and parasitic adaptations. Genomics 2021; 113:3666-3680. [PMID: 34403763 DOI: 10.1016/j.ygeno.2021.08.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 07/06/2021] [Accepted: 08/03/2021] [Indexed: 12/13/2022]
Abstract
Copepods encompass numerous ecological roles including parasites, detrivores and phytoplankton grazers. Nonetheless, copepod genome assemblies remain scarce. Lepeophtheirus salmonis is an economically and ecologically important ectoparasitic copepod found on salmonid fish. We present the 695.4 Mbp L. salmonis genome assembly containing ≈60% repetitive regions and 13,081 annotated protein-coding genes. The genome comprises 14 autosomes and a ZZ-ZW sex chromosome system. Assembly assessment identified 92.4% of the expected arthropod genes. Transcriptomics supported annotation and indicated a marked shift in gene expression after host attachment, including apparent downregulation of genes related to circadian rhythm coinciding with abandoning diurnal migration. The genome shows evolutionary signatures including loss of genes needed for peroxisome biogenesis, presence of numerous FNII domains, and an incomplete heme homeostasis pathway suggesting heme proteins to be obtained from the host. Despite repeated development of resistance against chemical treatments L. salmonis exhibits low numbers of many genes involved in detoxification.
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Affiliation(s)
| | - Ketil Malde
- Institute of Marine Research, Postboks 1870 Nordnes, 5817 Bergen, Norway; Sea Lice Research Centre. Department of Biological Sciences, University of Bergen, Thormøhlens Gate 53, 5006 Bergen, Norway
| | - Christiane Eichner
- Sea Lice Research Centre. Department of Biological Sciences, University of Bergen, Thormøhlens Gate 53, 5006 Bergen, Norway
| | - Michael Dondrup
- Computational Biology Unit, Department of Informatics, University of Bergen, Thormøhlens Gate 55, 5008 Bergen, Norway
| | - Tomasz Furmanek
- Institute of Marine Research, Postboks 1870 Nordnes, 5817 Bergen, Norway
| | - Francois Besnier
- Institute of Marine Research, Postboks 1870 Nordnes, 5817 Bergen, Norway
| | - Anna Zofia Komisarczuk
- Sea Lice Research Centre. Department of Biological Sciences, University of Bergen, Thormøhlens Gate 53, 5006 Bergen, Norway
| | - Michael Nuhn
- EMBL-The European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, CB10 1SD, UK
| | - Sussie Dalvin
- Institute of Marine Research, Postboks 1870 Nordnes, 5817 Bergen, Norway
| | - Rolf B Edvardsen
- Institute of Marine Research, Postboks 1870 Nordnes, 5817 Bergen, Norway
| | - Sven Klages
- Sequencing Core Facility, Max Planck Institute for Molecular Genetics, 14195 Berlin, Germany
| | - Bruno Huettel
- Max Planck Genome Centre Cologne, Carl von Linné Weg 10, D-50829 Köln, Germany
| | - Kurt Stueber
- Max Planck Genome Centre Cologne, Carl von Linné Weg 10, D-50829 Köln, Germany
| | - Sindre Grotmol
- Sea Lice Research Centre. Department of Biological Sciences, University of Bergen, Thormøhlens Gate 53, 5006 Bergen, Norway
| | - Egil Karlsbakk
- Sea Lice Research Centre. Department of Biological Sciences, University of Bergen, Thormøhlens Gate 53, 5006 Bergen, Norway
| | - Paul Kersey
- EMBL-The European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, CB10 1SD, UK; Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AE, UK
| | - Jong S Leong
- Department of Biology, University of Victoria, Victoria, British Columbia V8W 3N5, Canada
| | - Kevin A Glover
- Institute of Marine Research, Postboks 1870 Nordnes, 5817 Bergen, Norway; Sea Lice Research Centre. Department of Biological Sciences, University of Bergen, Thormøhlens Gate 53, 5006 Bergen, Norway
| | - Richard Reinhardt
- Max Planck Genome Centre Cologne, Carl von Linné Weg 10, D-50829 Köln, Germany
| | - Sigbjørn Lien
- Centre for Integrative Genetics (CIGENE), Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, Oluf Thesens vei 6, 1433 Ås, Norway
| | - Inge Jonassen
- Computational Biology Unit, Department of Informatics, University of Bergen, Thormøhlens Gate 55, 5008 Bergen, Norway
| | - Ben F Koop
- Department of Biology, University of Victoria, Victoria, British Columbia V8W 3N5, Canada
| | - Frank Nilsen
- Institute of Marine Research, Postboks 1870 Nordnes, 5817 Bergen, Norway; Sea Lice Research Centre. Department of Biological Sciences, University of Bergen, Thormøhlens Gate 53, 5006 Bergen, Norway.
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Dalvin S, Eichner C, Dondrup M, Øvergård AC. Roles of three putative salmon louse (Lepeophtheirus salmonis) prostaglandin E 2 synthases in physiology and host-parasite interactions. Parasit Vectors 2021; 14:206. [PMID: 33874988 PMCID: PMC8056522 DOI: 10.1186/s13071-021-04690-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Accepted: 03/16/2021] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND The salmon louse (Lepeophtheirus salmonis) is a parasite of salmonid fish. Atlantic salmon (Salmo salar) exhibit only a limited and ineffective immune response when infested with this parasite. Prostaglandins (PGs) have many biological functions in both invertebrates and vertebrates, one of which is the regulation of immune responses. This has led to the suggestion that prostaglandin E2 (PGE2) is important in the salmon louse host-parasite interaction, although studies of a salmon louse prostaglandin E2 synthase (PGES) 2 gene have not enabled conformation of this hypothesis. The aim of the present study was, therefore, to characterize two additional PGES-like genes. METHODS Lepeophtheirus salmonis microsomal glutathione S-transferase 1 like (LsMGST1L) and LsPGES3L were investigated by sequencing, phylogenetics, transcript localization and expression studies. Moreover, the function of these putative PGES genes in addition to the previously identified LsPGES2 gene was analyzed in double stranded (ds) RNA-mediated knockdown (KD) salmon louse. RESULTS Analysis of the three putative LsPGES genes showed a rather constitutive transcript level throughout development from nauplius to the adult stages, and in a range of tissues, with the highest levels in the ovaries or gut. DsRNA-mediated KD of these transcripts did not produce any characteristic changes in phenotype, and KD animals displayed a normal reproductive output. The ability of the parasite to infect or modulate the immune response of the host fish was also not affected by KD. CONCLUSIONS Salmon louse prostaglandins may play endogenous roles in the management of reproduction and oxidative stress and may be a product of salmon louse blood digestions.
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Affiliation(s)
- Sussie Dalvin
- Institute of Marine Research, SLCR-Sea Lice Research Centre, Nordnes, P. box 1870, 5817, Bergen, Norway
| | - Christiane Eichner
- Department of Biological Sciences, SLCR-Sea Lice Research Centre, University of Bergen, P. box 7803, 5020, Bergen, Norway
| | - Michael Dondrup
- Department of Informatics, SLRC-Sea Lice Research Centre, University of Bergen, P. box 7803, 5020, Bergen, Norway
| | - Aina-Cathrine Øvergård
- Department of Biological Sciences, SLCR-Sea Lice Research Centre, University of Bergen, P. box 7803, 5020, Bergen, Norway.
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Harðardóttir HM, Male R, Nilsen F, Dalvin S. Chitin Synthases Are Critical for Reproduction, Molting, and Digestion in the Salmon Louse ( Lepeophtheirus salmonis). Life (Basel) 2021; 11:life11010047. [PMID: 33450932 PMCID: PMC7828418 DOI: 10.3390/life11010047] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 01/08/2021] [Accepted: 01/11/2021] [Indexed: 11/30/2022] Open
Abstract
Chitin synthase (CHS) is a large transmembrane enzyme that polymerizes Uridine diphosphate N-acetylglucosamine into chitin. The genomes of insects often encode two chitin synthases, CHS1 and CHS2. Their functional roles have been investigated in several insects: CHS1 is mainly responsible for synthesizing chitin in the cuticle and CHS2 in the midgut. Lepeophtheirus salmonis is an ectoparasitic copepod on salmonid fish, which causes significant economic losses in aquaculture. In the present study, the tissue-specific localization, expression, and functional role of L. salmonis chitin synthases, LsCHS1 and LsCHS2, were investigated. The expressions of LsCHS1 and LsCHS2 were found in oocytes, ovaries, intestine, and integument. Wheat germ agglutinin (WGA) chitin staining signals were detected in ovaries, oocytes, intestine, cuticle, and intestine in adult female L. salmonis. The functional roles of the LsCHSs were investigated using RNA interference (RNAi) to silence the expression of LsCHS1 and LsCHS2. Knockdown of LsCHS1 in pre-adult I lice resulted in lethal phenotypes with cuticle deformation and deformation of ovaries and oocytes in adult lice. RNAi knockdown of LsCHS2 in adult female L. salmonis affected digestion, damaged the gut microvilli, reduced muscular tissues around the gut, and affected offspring. The results demonstrate that both LsCHS1 and LsCHS2 are important for the survival and reproduction in L. salmonis.
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Affiliation(s)
- Hulda María Harðardóttir
- Sea Lice Research Centre, Department of Biological Sciences, University of Bergen, P.O. Box 7803, N-5020 Bergen, Norway; (R.M.); (F.N.)
- Correspondence:
| | - Rune Male
- Sea Lice Research Centre, Department of Biological Sciences, University of Bergen, P.O. Box 7803, N-5020 Bergen, Norway; (R.M.); (F.N.)
| | - Frank Nilsen
- Sea Lice Research Centre, Department of Biological Sciences, University of Bergen, P.O. Box 7803, N-5020 Bergen, Norway; (R.M.); (F.N.)
| | - Sussie Dalvin
- Sea Lice Research Centre, Institute of Marine Research, P.O. Box 1870, Nordnes, N-5817 Bergen, Norway;
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Wang Y, Chen F, He J, Xue G, Chen J, Xie P. Cellular and molecular modification of egg envelope hardening in fertilization. Biochimie 2020; 181:134-144. [PMID: 33333173 DOI: 10.1016/j.biochi.2020.12.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 12/07/2020] [Accepted: 12/13/2020] [Indexed: 11/30/2022]
Abstract
Fertilization is an essential process that fundamentally impacts fitness. An egg changes dramatically after fertilization mediating the beginning of life, which mainly includes the transformation of the egg envelope via hardening, which is thought to be due to complex reactions involved in the conversion of cellular and molecular. This review highlights the mechanisms of egg envelope hardening in teleost fish. We conclude that the egg envelope hardening might be carried out in two steps. (a) A metalloprotease (alveolin) hydrolyzes the N-terminal proline-glutamine (Pro-Gln) region of zona pellucida (ZP) 1 and (b) triggers intermolecular cross-linking to ZP3 catalyzed by transglutaminase (TGase). The post-fertilization hardening of the egg envelope is an evolutionarily conserved phenomenon across species. We discuss the biochemical function and interaction of some factors reported to be essential to egg envelope hardening in mammalian and nonmammalian species, including metalloprotease, TGase, peroxidase/ovoperoxidase, and other factors (carbohydrate moieties, zinc and Larp6 proteins), and the relevant data suggest that egg envelope hardening is crucial to block polyspermy in internal fertilization, in addition to protecting the developing embryo from mechanical shock and preventing bacterial infection in external fertilization. Increased knowledge of the processes of egg envelope hardening and fertilization is likely to make a remarkable contribution to reproduction and aquaculture.
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Affiliation(s)
- Yeke Wang
- Donghu Experimental Station of Lake Ecosystems, State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Feng Chen
- Donghu Experimental Station of Lake Ecosystems, State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jun He
- Donghu Experimental Station of Lake Ecosystems, State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China
| | - Ge Xue
- Donghu Experimental Station of Lake Ecosystems, State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jun Chen
- Donghu Experimental Station of Lake Ecosystems, State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China
| | - Ping Xie
- Donghu Experimental Station of Lake Ecosystems, State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China; Institute of Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environment, Yunnan University, Kunming, 650500, PR China.
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Identification and Description of the Key Molecular Components of the Egg Strings of the Salmon Louse ( Lepeophtheirus salmonis). Genes (Basel) 2019; 10:genes10121004. [PMID: 31817028 PMCID: PMC6947537 DOI: 10.3390/genes10121004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 11/21/2019] [Accepted: 11/30/2019] [Indexed: 12/12/2022] Open
Abstract
The salmon louse Lepeophtheirus salmonis is a parasite of Atlantic salmon and other salmonids. Every year, it causes high costs for the Norwegian aquaculture industry. While the morphology of the female genital tract has been described, knowledge of the molecular basis of reproduction is very limited. We identified nine genes which are expressed exclusively in the female cement gland, the organ responsible for cement production, which is used to hold the eggs together and keep them attached to their mother in egg strings. Six of these genes encode proteins with signal peptides and probably form the main component of the cement. Two other genes are peroxidases, which are probably important in the cement formation. The last gene is not similar to any known protein, but contains a transmembrane domain. A knockdown of all these genes leads to missing or deformed egg strings, preventing reproduction of the lice. The correct assemblage of the cement in the cement gland is essential for successful reproduction of salmon lice. Similar proteins seem to be present in other copepod species, as well.
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Poley JD, Braden LM, Messmer AM, Igboeli OO, Whyte SK, Macdonald A, Rodriguez J, Gameiro M, Rufener L, Bouvier J, Wadowska DW, Koop BF, Hosking BC, Fast MD. High level efficacy of lufenuron against sea lice (Lepeophtheirus salmonis) linked to rapid impact on moulting processes. Int J Parasitol Drugs Drug Resist 2018; 8:174-188. [PMID: 29627513 PMCID: PMC6039351 DOI: 10.1016/j.ijpddr.2018.02.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Revised: 02/26/2018] [Accepted: 02/28/2018] [Indexed: 11/29/2022]
Abstract
Drug resistance in the salmon louse Lepeophtheirus salmonis is a global issue for Atlantic salmon aquaculture. Multiple resistance has been described across most available compound classes with the exception of the benzoylureas. To target this gap in effective management of L. salmonis and other species of sea lice (e.g. Caligus spp.), Elanco Animal Health is developing an in-feed treatment containing lufenuron (a benzoylurea) to be administered prior to seawater transfer of salmon smolts and to provide long-term protection of salmon against sea lice infestations. Benzoylureas disrupt chitin synthesis, formation, and deposition during all moulting events. However, the mechanism(s) of action are not yet fully understood and most research completed to date has focused on insects. We exposed the first parasitic stage of L. salmonis to 700 ppb lufenuron for three hours and observed over 90% reduction in survival to the chalimus II life stage on the host, as compared to vehicle controls. This agrees with a follow up in vivo administration study on the host, which showed >95% reduction by the chalimus I stage. Transcriptomic responses of salmon lice exposed to lufenuron included genes related to moulting, epithelial differentiation, solute transport, and general developmental processes. Global metabolite profiles also suggest that membrane stability and fluidity is impacted in treated lice. These molecular signals are likely the underpinnings of an abnormal moulting process and cuticle formation observed ultrastructurally using transmission electron microscopy. Treated nauplii-staged lice exhibited multiple abnormalities in the integument, suggesting that the coordinated assembly of the epi- and procuticle is impaired. In all cases, treatment with lufenuron had rapid impacts on L. salmonis development. We describe multiple experiments to characterize the efficacy of lufenuron on eggs, larvae, and parasitic stages of L. salmonis, and provide the most comprehensive assessment of the physiological responses of a marine arthropod to a benzoylurea chemical.
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Affiliation(s)
- Jordan D Poley
- Hoplite Lab, Department of Pathology & Microbiology, Atlantic Veterinary College, University of Prince Edward Island, 550 University Ave, Charlottetown PE, C1A 4P3, Canada.
| | - Laura M Braden
- Hoplite Lab, Department of Pathology & Microbiology, Atlantic Veterinary College, University of Prince Edward Island, 550 University Ave, Charlottetown PE, C1A 4P3, Canada.
| | - Amber M Messmer
- Centre for Biomedical Research, Department of Biology, University of Victoria, Victoria BC, V8W 3N5, Canada.
| | - Okechukwu O Igboeli
- Hoplite Lab, Department of Pathology & Microbiology, Atlantic Veterinary College, University of Prince Edward Island, 550 University Ave, Charlottetown PE, C1A 4P3, Canada.
| | - Shona K Whyte
- Hoplite Lab, Department of Pathology & Microbiology, Atlantic Veterinary College, University of Prince Edward Island, 550 University Ave, Charlottetown PE, C1A 4P3, Canada.
| | - Alicia Macdonald
- Elanco Canada Limited, 150 Research Lane, Guelph, Ontario N1G 4T2, Canada.
| | - Jose Rodriguez
- Elanco Canada Limited, 150 Research Lane, Guelph, Ontario N1G 4T2, Canada.
| | - Marta Gameiro
- Elanco Canada Limited, 150 Research Lane, Guelph, Ontario N1G 4T2, Canada.
| | - Lucien Rufener
- Elanco Centre de Recherche Santé Animale SA, CH-1566 St.-Aubin, Switzerland; INVENesis LLC, Chemin de Belleroche 14, 2000 Neuchâtel, Switzerland.
| | - Jacques Bouvier
- Elanco Centre de Recherche Santé Animale SA, CH-1566 St.-Aubin, Switzerland; INVENesis LLC, Chemin de Belleroche 14, 2000 Neuchâtel, Switzerland.
| | - Dorota W Wadowska
- Electron Microscopy Laboratory, Atlantic Veterinary College, University of Prince Edward Island, 550 University Ave, Charlottetown, PEI, C1A 4P3, Canada.
| | - Ben F Koop
- Centre for Biomedical Research, Department of Biology, University of Victoria, Victoria BC, V8W 3N5, Canada.
| | - Barry C Hosking
- Elanco Canada Limited, 150 Research Lane, Guelph, Ontario N1G 4T2, Canada.
| | - Mark D Fast
- Hoplite Lab, Department of Pathology & Microbiology, Atlantic Veterinary College, University of Prince Edward Island, 550 University Ave, Charlottetown PE, C1A 4P3, Canada.
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Eichner C, Dondrup M, Nilsen F. RNA sequencing reveals distinct gene expression patterns during the development of parasitic larval stages of the salmon louse (Lepeophtheirus salmonis). JOURNAL OF FISH DISEASES 2018; 41:1005-1029. [PMID: 29368347 DOI: 10.1111/jfd.12770] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Revised: 11/08/2017] [Accepted: 11/10/2017] [Indexed: 06/07/2023]
Abstract
The salmon louse (Lepeophtheirus salmonis), an ectoparasitic copepod on salmonids, has become a major threat for the aquaculture industry. In search for new drugs and vaccines, transcriptome analysis is increasingly used to find differently regulated genes and pathways in response to treatment. However, the underlying gene expression changes going along with developmental processes could confound such analyses. The life cycle of L. salmonis consists of eight stages divided by moults. The developmental rate of salmon lice on the host is not uniform. Individual- and sex-related differences are found leading to individuals of unlike developmental status at same sampling time point after infection. In this study, we analyse L. salmonis from a time series by RNA sequencing applying a method of separating individuals of different instar age independent of sampling time point. Lice of four stages divided into up to four age groups within the stage were analysed in triplicate (total of 66 samples). Gene expression analysis shows that the method for sorting individuals was successful. Many genes show cyclic expression patterns over the moulting cycles. Overall gene expression differs more between lice of different age within the same stage than between lice of different stage but same instar age.
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Affiliation(s)
- C Eichner
- Sea Lice Research Centre, Department of Molecular Biology, University of Bergen, Bergen, Norway
| | - M Dondrup
- Sea Lice Research Centre, Department of Informatics, University of Bergen, Bergen, Norway
| | - F Nilsen
- Sea Lice Research Centre, Department of Biology, University of Bergen, Bergen, Norway
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Deltamethrin resistance in the salmon louse, Lepeophtheirus salmonis (Krøyer): Maternal inheritance and reduced apoptosis. Sci Rep 2018; 8:8450. [PMID: 29855496 PMCID: PMC5981211 DOI: 10.1038/s41598-018-26420-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 05/08/2018] [Indexed: 01/15/2023] Open
Abstract
Resistance towards deltamethrin (DMT) in the crustacean ectoparasite Lepeophtheirus salmonis (Caligidae) is a problem on fish farms lining the North Atlantic Ocean. Two Norwegian strains with different susceptibility towards DMT were crossed in the parental generation (P0), females from a sensitive strain were crossed with males from a resistant strain and vice versa. Individual susceptibility towards DMT was assessed in the second filial generation (F2). DMT resistance was only found in F2 descendants when the P0 females were from the resistant strain, pointing to maternal inheritance. Since maternal inheritance might be linked to the mitochondrial (mt) genome, the nucleotide sequences and the gene expressions of mt-genes were analysed. Twenty non-synonymous single nucleotide polymorphisms (SNPs) were identified in mt-transcripts from resistant F2 parasites, including SNPs in two cytochrome C oxidase subunits (COX1 and COX3) and two subunits of the NADH dehydrogenase complex (ND1 and ND5) previously linked to DMT resistance in the salmon louse. Differential expression analysis between the sensitive and resistant strain revealed strain effect in seven out of twelve mt-genes. The current study also show that DNA fragmentation (indicating apoptosis) was affected by DMT exposure in skeletal muscle tissue and that resistant parasites undergo less apoptosis than sensitive parasites.
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