Unknown,Transcriptomics,Genomics,Proteomics

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Salmon Spawning Migration: Metabolic Shifts and Environmental Triggers

ABSTRACT: 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.

ORGANISM(S): Oncorhynchus nerka

SUBMITTER: David Patterson

PROVIDER: E-GEOD-13657 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:The transcriptional response of Atlantic salmon (Salmo salar) to infectious hematopoietic necrosis (IHN) virus was elucidated using 16,008 gene GRASP cDNA microarrays. S. salar were exposed to the IHN virus in a waterborne challenge, and kidney samples from five fish sampled on each of days 0, 1, 5 and 9 were analysed in the microarray study. Validation of nine of the significant genes was conducted on fish sampled on alternate days from 1 to 13 and compared to the unchallenged control sampled on day 0. The key pathways up-regulated in response to the virus included endosomal transport, type I and II interferon responses, the alternative complement pathway, apoptosis, phagocytosis and phagocytic cell oxidation, natural killer cell activity, antiviral replication via iron sequestering, virally-induced disruption of the cell cycle, retroviral DNA integration, T-cell activation and cellular immunity. Fish that did not contain viral titer on days 5 and 9 responded in a similar manner to those with titer, but further induced a number of genes involved in anti-viral replication (Glutathione peroxidase 1 and ferritin H), anti-proliferation (PTEN and B-cell receptor associated protein 32), lysosomal response (CD63 antigen), pro-inflammatory response (lipopolysaccharide binding protein, stress activated JNK1, thiol peroxidase), and T-cell activation (T-cell activation Rho-GTPase activating protein) that may increase resistance to the virus. Three genes that were potentially co-opted by the virus to enhance infectivity were also identified, including uPAR (angiogenesis), CypA (viral replication and infectivity), and BAF1 (viral protein biosynthesis). Perhaps the most notable finding was the up-regulation of uPAR which can function to increase the density of fibronectin, the receptor of the IHN virus, on the cell surface, hence facilitate viral entry into the cell. Keywords: Immunlogical response to IHN virus challenge A preliminary microarray experiment was run on the waterborne-challenged S. salar whereby the five individuals sampled on a given day were combined and run on a single slide, and we compared the expression profiles from each day (days 0 (unchallenged control) through 11). From this experiment, we noted that the most profound changes were occurring around days 1, 5, and 9, so we performed subsequent experiments at these time points, with five fish per day and 5 control fish analysed in total.

Project description:The long-term viability of Pacific salmon stocks and the fisheries they support are threatened if large numbers die prematurely en-route to spawning grounds. Physiological profiles that were correlated with the fate of wild sockeye salmon during river migration were discovered using functional genomics studies on biopsied tissues. Three independent biotelemetry studies tracked the biopsied fish after tagging in the marine environment over 200 km from the Fraser River, in the lower river 69 km from the river mouth and at the spawning grounds. Salmon carrying the poor performance (unhealthy) profile in the ocean exhibited a 4-times lower probability of arriving to spawning grounds than those with a healthy genomic signature, although generally migrated into the river and to the spawning grounds faster. A related unhealthy signature observed in the river was associated with a 30% reduction in survival to spawning grounds in one of the three stocks tested. At spawning grounds, the same poor performance signature was associated with twice the pre-spawning mortality compared with healthy fish. Functional analysis revealed that the unhealthy signature, which intensified during migration to spawning grounds, was consistent with an intracellular pathogenic infection, likely a virus. These results are the first to suggest a pathogen present in salmon in the marine environment could be a major source of mortality during migration and spawning in the river. This series are gill expression profiles from the study of fish at the Weaver creek spawning grounds, and were observed for pre-spawning mortality or successful spawning. Weaver creek sockeye salmon (a late-run stock) spawn in an artificial spawning channel which has a controlled entrance and no exit, situated 100 km from the ocan. Females were dip-netted out of the entrance of the spawning channel, and placed into a sampling trough with flowing ambient water for the gill biopsy procedure and tagged with Petersen discs and returned to the spawning channel. Moribund fish were recovered daily and their gonads examined to assess whether they had spawned or not. Gene expression was assayed on the GRASP salmonid 32K cDNA microarray.

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Project description:The long-term viability of Pacific salmon stocks and the fisheries they support are threatened if large numbers die prematurely en-route to spawning grounds. Physiological profiles that were correlated with the fate of wild sockeye salmon during river migration were discovered using functional genomics studies on biopsied tissues. Three independent biotelemetry studies tracked the biopsied fish after tagging in the marine environment over 200 km from the Fraser River, in the lower river 69 km from the river mouth and at the spawning grounds. Salmon carrying the poor performance (unhealthy) profile in the ocean exhibited a 4-times lower probability of arriving to spawning grounds than those with a healthy genomic signature, although generally migrated into the river and to the spawning grounds faster. A related unhealthy signature observed in the river was associated with a 30% reduction in survival to spawning grounds in one of the three stocks tested. At spawning grounds, the same poor performance signature was associated with twice the pre-spawning mortality compared with healthy fish. Functional analysis revealed that the unhealthy signature, which intensified during migration to spawning grounds, was consistent with an intracellular pathogenic infection, likely a virus. These results are the first to suggest a pathogen present in salmon in the marine environment could be a major source of mortality during migration and spawning in the river. This series is of gill expression profiles from the study of fish sampled and tagged in the ocean and tracked as they entered the river system and swam towards the spawning grounds. Fish were caught in seine nets, gastrically implanted with radio transmitters, and biopsy sampled for blood, gill, muscle, and fin. Individual fish were tracked by receivers placed throughout the Fraser River watershed to identify and fate (i.e. the location of the receiver that last detected the fish). Targeted stocks of interest were genetically identified. Gene expression was profiled in gill tissue, a critical respiratory and ionoregulatory organ that is highly responsive to stress, chemical exposure and disease. Gene expression was assayed on the GRASP salmonid 16K cDNA microarray.

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Salmon Spawning Migration: Metabolic Shifts and Environmental Triggers

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