Abstract
The objective of this study was to identify genetic variants associated with long-chain omega-3 fatty acid content in Atlantic salmon muscle, in order to identify genes underlying the genetic variation in these traits, by performing a genome-wide association study.Fatty acid composition, including eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) content and the ratios DHA/DPA (docosapentaenoic acid) and DHA/ALA (α-linolenic acid) of skeletal muscle was determined in 642 Atlantic salmon individuals from the Salmobreed broodstock program. Further, a 57 K single-nucleotide polymorphism (SNP) array was used to genotype the 642 individuals to search for SNPs associated with skeletal muscle content of individual omega-3 fatty acids as well as ratios between fatty acids, using a mixed model approach. We identified markers showing a significant association with the ratio of DHA to DPA located on chromosome 19, close to the candidate gene elovl2, which is directly involved in the conversion of DPA to DHA. The results further suggested that genetic variation affecting fillet EPA and DHA content is present on Atlantic salmon chromosome 21, as the GWAS analysis of EPA, DHA and DHA/ALA ratio all pointed to this chromosome. No known genes of direct relevance to the omega-3 bioconversion pathway were found here. We discuss the relevance of other interesting genes related to lipid metabolism and health located in this region.
Highlights
Atlantic salmon (Salmo salar L.) is an important farmed fish species, known for its high content of the health-promoting omega-3 long-chain polyunsaturated fatty acids (n-3 LC PUFA) eicosapentaenoic (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) in muscle
One of the genes in this interval is fatty acid elongase 2, which is directly involved in the conversion of DPA to DHA by elongating DPA to 24:5n-3, and is a strong candidate to explain this association
Our results suggest that skeletal muscle n-3 LC PUFA content traits have a polygenic architecture with potentially a few quantitative trait loci (QTL) explaining moderate levels of the genetic variation in Atlantic salmon
Summary
Atlantic salmon (Salmo salar L.) is an important farmed fish species, known for its high content of the health-promoting omega-3 long-chain polyunsaturated fatty acids (n-3 LC PUFA) eicosapentaenoic (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) in muscle. The omega-3 bioconversion pathway enables salmonids to convert the shorter-chained fatty acid alpha-linolenic acid (ALA; 18:3n-3), into EPA and DHA (Bou et al, 2017; Monroig et al, 2013; Tocher et al, 2003). The genes of the omega-3 bioconversion pathway are expressed in skeletal muscle tissue of Atlantic salmon (Codabaccus et al, 2011; Horn et al, 2019)
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