Differentiating size-dependent responses of juvenile pink salmon (Oncorhynchus gorbuscha) to sea lice (Lepeophtheirus salmonis) infections
ABSTRACT: Salmon infected with an ectoparasitic marine copepod, the salmon louse Lepeophtheirus salmonis, incur a wide variety of consequences depending upon host sensitivity. Juvenile pink salmon (Oncorhynchus gorbuscha) migrate from natal freshwater systems to the ocean at a young age relative to other Pacific salmon, and require rapid development of appropriate defences against marine pathogens. We analyzed the early transcriptomic responses of naïve juvenile pink salmon of sizes 0.3g (no scales), 0.7g (mid-scale development) and 2.4g (scales fully developed) to a low-level laboratory exposure with early moult stage L. salmonis. All infected size groups exhibited unique transcriptional profiles. Inflammation and inhibition of cell proliferation was identified in the smallest size class (0.3g), while increased glucose absorption and retention was identified in the middle size class (0.7g). Tissue-remodelling genes were also up-regulated in both the 0.3g and 0.7g size groups. Profiles of the 2.4g size class indicated cell-mediated immunity and possibly parasite-induced growth augmentation. Understanding a size-based threshold of resistance to L. salmonis is important for fisheries management. This work characterizes molecular responses reflecting the gradual development of innate immunity to L. salmonis between the susceptible (0.3g) and refractory (2.4g) pink salmon size classes. Six-condition experiment, 3 size groups each infected and uninfected, duplicate tanks. Biological replicates: 6 control, 6 infected for each size group. Sampled 6 days post exposure. cDNA samples with reference design (aRNA), two-color array.
Project description:Salmon infected with an ectoparasitic marine copepod, the salmon louse Lepeophtheirus salmonis, incur a wide variety of consequences depending upon host sensitivity. Juvenile pink salmon (Oncorhynchus gorbuscha) migrate from natal freshwater systems to the ocean at a young age relative to other Pacific salmon, and require rapid development of appropriate defences against marine pathogens. We analyzed the early transcriptomic responses of naïve juvenile pink salmon of sizes 0.3g (no scales), 0.7g (mid-scale development) and 2.4g (scales fully developed) to a low-level laboratory exposure with early moult stage L. salmonis. All infected size groups exhibited unique transcriptional profiles. Inflammation and inhibition of cell proliferation was identified in the smallest size class (0.3g), while increased glucose absorption and retention was identified in the middle size class (0.7g). Tissue-remodelling genes were also up-regulated in both the 0.3g and 0.7g size groups. Profiles of the 2.4g size class indicated cell-mediated immunity and possibly parasite-induced growth augmentation. Understanding a size-based threshold of resistance to L. salmonis is important for fisheries management. This work characterizes molecular responses reflecting the gradual development of innate immunity to L. salmonis between the susceptible (0.3g) and refractory (2.4g) pink salmon size classes. Overall design: Six-condition experiment, 3 size groups each infected and uninfected, duplicate tanks. Biological replicates: 6 control, 6 infected for each size group. Sampled 6 days post exposure. cDNA samples with reference design (aRNA), two-color array.
Project description:A large-scale functional genomics study revealed shifting energy generating processes in white muscle during the final 1,300 km migration of wild sockeye salmon to their spawning grounds in the Fraser River, British Columbia. In 2006, Lower Adams stock sockeye salmon ceased feeding after passing the Queen Charlotte Islands, 850 km from the Fraser River. Enhanced protein turnover and reduced transcription of actin, muscle contractile and heme-related proteins were early starvation responses in saltwater. Arrival to the estuarine environment triggered massive protein turnover through induction of proteasoma and lysosomal proteolysis and protein biosynthesis, and a shift from anaerobic glycolysis to oxidative phosphorylation. Response to entry into freshwater was modest, with up-regulation of heat shock proteins and nitric oxide biosynthesis. High river temperatures resulted in a strong defense/immune response and high mortalities in 50% of fish. Arrival to the spawning grounds triggered further up-regulation of oxidative phosphorylation and proteolysis, down-regulation of protein biosynthesis and helicase activity, and continued down-regulation of muscle proteins and most glycolytic enzymes. However, sharp up-regulation of PFK-I indicated induction of glycolytic potential at the spawning grounds. The identification of potential environmental cues triggering genome-wide transcriptional shifts in white muscle associated with migration and the strong activation of proteasomal proteolysis were both novel findings. Keywords: Functional genomics study on wild-caught fish The experiment was based on expression profiles of white muscle tissue collected from wild migrating adult sockeye salmon during their return spawning migration back to the Fraser River. Fish were collected from seven sites along the final 1,300 km migration path, and white muscle samples were quickly frozen in liquid nitrogen upon capture. Marine sampling sites included (from north to south) the Queen Charlotte Islands (QCI), Johnstone Strait (JS), Juan de Fuca Strait (JDFS), and the Strait of Georgia (SOG). Freshwater sampling sites included Whonnock (W), Savona (SV) and the Lower Adams Spawning Grounds. Genetically-based stock ID was used to identify the natal sites of fish collected from the wild. The experiment was designed to profile the transcriptional shifts associated with migration of the Adams River stock complex. The total experiment included 80 microarray slides, with a minimum biological replicate size per site of 6 (SV), and maximum of 18 (JS) (see supplemental table for details). Additional intra-site variables, which could only be addressed in some sites, included sex (female biased) and river entry timing (for JS, JDFS and W sites; identified through radio-tracking of marine collected fish). Total RNA was amplified (1 round) with MessageAmpTMII-96 kit (Ambion, TX, USA), and reverse transcribed to cDNA before labelling with ALEXA dyes using the Invitrogen Indirect Labelling Kit. The experiment was based on a reference design, with the reference containing the combined aRNA of all individuals used in the experiment. Individual samples were labelled with Alexa 555 and the reference control with Alexa 647, with no dye flips included. A single technical replicate of one SV fish (replicate 5) was included in the experimental design. This experiment is part of a larger white muscle experiment containing additional sockeye salmon stocks.
Project description:The aquaculture industry has confronted severe economic losses due to infectious diseases in the last years. Piscirickettsiosis or Salmonid Rickettsial Septicaemia (SRS) is the bacterial disease caused by Piscirickettsia salmonis. This Gram-negative, non-motile, cellular pathogen has the ability to infect, survive, replicate, and propagate in salmonid monocytes/macrophages generating a systemic infection characterized by the colonization of several organs including kidney, liver, spleen, intestine, brain, ovary and gills. In this study, we attempted to determine whether global gene expression differences can be detected in different genetic groups of Atlantic salmon as a result of Piscirickettsia salmonis infection. Moreover, we sought to characterize the fish transcriptional response in order to reveal the mechanisms that might confer resistance in Atlantic salmon to an infection with Piscirickettsia salmonis. In doing so, after challenging with Piscirickettsia salmonis, we selected the families with the highest (HS) and the lowest (LS) recorded susceptibility for gene expression analysis using 32K cGRASP microarrays. Our results revealed in LS families expression changes are linked to iron depletion, as well as, low contents of iron in kidney cells and low bacterial load, indicated that the iron-withholding strategy of innate immunity is part of the mechanism of resistance against Piscirickettsia salmonis. This information contributes to elucidate the underlying mechanisms of resistance to Piscirickettsia salmonis infection in Atlantic salmon and to identify new candidate genes for selective breeding programmes. Forty full-sibling families of Atlantic salmon (Salmo salar) were infected by intraperitoneal injection with 0.2 mL Piscirickettsia salmonis (PS889, isolated from Oncorhynchus kisutch, 1×104 PFU/mL). After forty days, the fishes were harvested and the cumulative mortality (dead fish / total fish) for each family was calculated. For the second challenge, the six families with the highest cumulative mortality levels were considered of relatively high susceptibility (HS) and the six families with the lowest cumulative mortality levels were considered of relatively low susceptibility (LS) to the infection. Five control and five infected fish from three HS and three LS families were analyzed. For each HS and LS family, pools of RNA from control and infected fish were prepared separately and were reverse transcribed. Four slides were for each used family hybridized including two dye-swaped slides. Labeled samples were hybridized on a 32K cDNA microarray, developed at the Consortium for Genomics Research on All Salmonids Project (cGRASP), GEO accession number: GPL8904.
Project description:This SuperSeries is composed of the following subset Series: GSE26981: Responses to ectoparasite salmon louse (Lepeophtheirus salmonis) in skin of Atlantic salmon GSE26984: Responses to ectoparasite salmon louse (Lepeophtheirus salmonis) in spleen of Atlantic salmon Refer to individual Series
Project description:We investigate the effect of a functional feed for immunostimulation (peptidoglycan extract from bacterial cell wall with nucleotide formulation) on L. salmonis infection levels on Atlantic salmon Salmo salar, and on host and parasite gene expression profiles. Atlantic salmon smolts (~95 g) were fed a control diet, or a low or high dose immunostimulant diet, and then exposed to L. salmonis copepodids in three subsequent exposures. The transcriptome of salmon lice late in the infection attached to either the low dose diet or control diet hosts were compared using a 38K oligonucleotide microarray. Overall design: Atlantic L. salmonis copepods were used to infect Atlantic salmon on an immunostimulant diet, and upon development to the adult stage the lice were collected and profiled. Lice are either feeding on immunostimulant-fed or control-fed salmon. Lice samples are equal numbers of males and females.
Project description:The present work characterizes the response of co-habited Atlantic (Salmo salar), chum (Oncorhynchus keta) and pink salmon (Oncorhynchus gorbuscha) to sea lice infections. Atlantic and pink salmon anterior kidney samples were profiled at three time points over nine days after the start of an experimental infection. Chum salmon anterior kidney was profiled at day six post infection only. All three species were also profiled at six days post exposure for skin responses of the pectoral fin, typically associated with lice infection. Overall design: Anterior kidney was profiled at day 3, 6, 9 post exposure to lice infection in Atlantic and pink salmon, but only at 6 days post exposure in chum salmon (for each day/species n = 10 for control, 10 for infected). Controls were treated exactly as experimental, but with the addition of seawater only (no lice). Time-matched controls were used for analysis. Please note that each tissue/species combination was normalized separately and then indirectly compared.
Project description:This study investigates the transcriptomic responses of salmon lice (L. salmonis) infecting salmon treated with emamectin benzoate (either 1x or 3x), ivermectin, or commercial feed controls Overall design: Copepodid-staged larvae of L. salmonis were used to infect Atlantic salmon fed 1x or 3x emamectin benzoate, ivermectin, or commercial feed controls. Pre-adult I lice were collected from each group, pooled by treatment group and sex (pools of 6 lice) and stored at -80C for RNA extraction and microarray analyses. A total of 48 pools were used (n = 6 per condition except n = 5 for male controls and n = 7 for male 3xEMB)
Project description:Caligid copepods, also called sea lice, are common ectoparasites of wild and farmed marine fish. The salmon louse Lepeophtheirus salmonis (Krøyer, 1837) has emerged as a serious problem for salmon farming in the Northern hemisphere. The annual cost of sea lice to the global salmon mariculture industry has been estimated at 300 million, of which the majority accounts for the cost of chemically treating the farmed salmon. The treatments available for salmonids with sea lice infestation have been limited with a large scale reliance on single products and the use of antiparasitics with similar modes of action, which when used over a long period of time can enhance the selection pressure for reduced sensitivity. Two L. salmonis laboratory strains, established from field isolates and differing in susceptibility to emamectin benzoate (EMB) were studied using a custom sea louse 15K oligonucleotide microarray and RT-qPCR. The aim of the present study was to identify differential expression of transcripts between these two strains to identify potential constitutive gene expression changes associated with reduced susceptibility to EMB. Adult male salmon lice were sampled without exposure to antiparasitic agents for the purpose of studying gene expression from unchallenged individuals. In this study changes in expression of Glutamate-gated Chloride channel (GluCl) subunits, considered the major target site for avermectin (AVM) drugs in invertebrates, was not observed, but expression changes were seen for alternative ligand-gated ion channel (LGIC) subunits that form an ion channels shown to interact with AVMs in vertebrates, but which is not traditionally considered to be a target site for AVMs in invertebrates. We hypothesise that these LGIC subunits represent additional EMB target sites in salmon lice, and that the down-regulation of these channel subunits in this EMB-resistant strain is related to the resistance phenotype.
Project description:This study investigates host-specific gene expression of the Pacific salmon lice, Lepeophtheirus salmonis oncorhynchii, while parasitizing a resistant host (Coho salmon), two susceptible hosts (Atlantic salmon, Sockeye salmon), and a population with-held hosts (starved), over 48 hrs. Overall design: Adult female sea lice were allowed to attach to three different host populations (Atlantic, Coho and Sockeye salmon), or were kept in incubation chambers devoid of hosts (starved). At 0, 24, and 48 hours, individual lice were sampled for subsequent RNA analysis.