Evolutionary history and diversification of duplicated fatty-acyl elongase genes of Atlantic salmon (Salmo salar)

• Main Author: Carmona-Antoñanzas, Greta E.
• Other Authors: Leaver, Michael J.
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Stirling 2014
• Subjects: Atlantic salmon; Transcription factor; Gene expression; Whole-genome duplication; Paralogous genes; Gene duplication; Salmonids; Evolution; Fatty Acids Metabolism Regulation; Salmo salar
• Online Access: http://hdl.handle.net/1893/19848; http://dspace.stir.ac.uk/bitstream/1893/19848/1/PhDthesis_Corrected_March2014.pdf

Background: The Atlantic salmon, Salmo salar L., is a prominent member of the Salmonidae family, and has been the focus of intense research because of its environmental and economic significance as an iconic sporting species and its global importance as an aquaculture species. Furthermore, salmonids constitute ideal organisms for the study of evolution by gene duplication as they are pseudotetraploid descendants of a common ancestor whose genome was duplicated some 25 to 100 million years ago. Whole-genome duplication is considered a major evolutionary force capable of creating vast amounts of new genetic material for evolution to act upon, promoting speciation by acquisition of new traits. Recently, large-scale comparison of paralogous genes in Atlantic salmon suggested that asymmetrical selection was acting on a significant proportion of them. However, to elucidate the physiological consequences of gene and genome duplications, studies integrating molecular evolution and functional biology are crucial. To this end, sequence and molecular analyses were performed on duplicated Elovl5 fatty-acyl elongases of Atlantic salmon, as they are responsible for a rate-limiting reaction in the elongation process of long-chain polyunsaturated fatty acids (LC-PUFA), critical components of all vertebrates. The aim of the research presented here was to investigate the role of gene duplication as an evolutionary process capable of creating genetic novelty, and to identify the potential ecological and physiological implications. Results: Linkage analyses indicated that both fatty-acyl elongases segregated independently and located elovl5 duplicates on different linkage groups. Genetic mapping using microsatellites identified in each elovl5 locus assigned elovl5a and elovl5b to chromosomes ssa28 and ssa13, respectively. In silico sequence analysis and selection tests indicated that both salmon Elovl5 proteins were subject to purifying selection, in agreement with previous results showing indistinguishable substrate specificities. ...