Project description:a salmonid microarray was used to characterize environmentally-regulated shifts in gene expression between ocean and river habitats in gill and liver tissues of wild migrating adult Pacific sockeye salmon (Oncorhynchus nerka). To correlate gene expression with survival, non-lethal biopsy sampling of gill tissue and microarray-based profiling was combined with biotelemetry and genetic stock identification so that transcriptomic profiles could be compared between fish reaching spawning grounds and presumed mortalities. Fish were captured fish at two marine sampling sites, one within Johnstone Strait (JS), BC. Canada and one within Juan De Fuca Strait (JDFS), BC Canada. Ocean sites were contrasted to fish sampled within the Fraser River at Whonnock (W), BC, Canada. Gill and liver tissues were dissected at each of these sites. Non-lethal biopsy sampling was performed on migrating sockeye salmon intercepted within the Fraser River at Mission, BC, Canada and genetically-based stock ID was used to determine the stock-specific spawning grounds for each fish, giving an intended end-point of migration for each of the stocks investigated in this study.Gene expression levels were determined by comparing the amount of mRNA transcript in the experimental samples relative to a reference sample. A total of 123 microarrays were used to generate the dataset, corresponding to individual hybridizations of both gill and liver samples collected from JS (gill n=14; liver n=15), JDFS (gill n=15; liver n=13), W (gill n=11; liver n=10), and biopsy sampled gill tissue collected at Mission (n=45).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 reference contained the combined aRNA of all individuals used in the experiment, excluding bioposy sampled fish. Individual samples were labelled with Alexa 555 and the reference control with Alexa 647, and no dye swaps were perfromed.

Project description:Pacific salmon undergo dramatic physiological remodeling during their terminal spawning migration, culminating in reproductive maturation, senescence, and death. To investigate the molecular mechanisms underlying these processes, we characterized transcriptomic changes in wild pink salmon (Oncorhynchus gorbuscha) sampled at three migratory stages (marine, riverine, and spawning ground) and across three tissues central to endocrine regulation and energy metabolism: gonads, head kidney, and skeletal muscle. RNA sequencing and dDifferential gene expression analyses waswere performed to identify biological pathways associated with maturation and semelparity. Transcriptomic changesremodeling wereas most pronounced during the final transition from river migrating fish entry to spawning, with the gonads exhibiting the greatest number of differentially expressed genes, followed by skeletal muscle and head kidney. Gene ontology analyses revealed coordinated upregulation of pathways associated with starvation responses, lipid mobilization, tissue catabolism, proteolysis, autophagy, and cell death across tissues. Immune and inflammatory processes were elevated in skeletal muscle and head kidney, while gonads showed strong enrichment of insulin signaling, steroid metabolism, and hormone-response pathways. Analysis of endocrine receptor expression identified tissue-specific and ohnolog-specific regulation of receptors involved in thyroid, growth hormone, insulin, gonadotropin, sex steroid, and glucocorticoid signaling, suggesting functional divergence among duplicated salmonid genes. These findings identified in pink salmon provide evidence that the demonstrate that the most extreme physiological changes occur extensive molecular reprogramming in pink salmon occurs duringat the time of final maturation rather than freshwater entry. The coordinated activation of endocrine, metabolic, and degenerative pathways supports a mechanistic link between reproductive development and semelparous senescence, providing new insight into the endocrine and transcriptomic networks that govern spawning-associated physiological decline in Pacific salmon.

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Oncorhynchus nerka

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