title: Transcriptome profiling in fast versus slow-growing rainbow trout across seasonal gradients.
abstract: BACKGROUND
  Circannual rhythms in vertebrates can influence a wide variety of physiological processes. Some notable examples include annual reproductive cycles and for poikilotherms, seasonal changes modulating growth. Increasing water temperature elevates growth rates in fishes, but increases in photoperiod regime can have similar influences even at constant temperature. Therefore, in order to understand the dynamics of growth in fish it is important to consider the background influence of photoperiod regime on gene expression differences. This study examined the influence of a declining photoperiod regime (winter solstice) compared to an increasing photoperiod regime (spring equinox) on white muscle transcriptome profiles in fast and slow-growing rainbow trout from a commercial aquaculture strain.
  
  
  RESULTS
  Slow-growing fish could be characterized as possessing transcriptome profiles that conform in many respects to an endurance training regime in humans. They have elevated mitochondrial and cytosolic creatine kinase expression levels and appear to suppress mTOR-signaling as evidenced by elevated TSC2 expression, and they also have elevated p53 levels. Large fish display a physiological repertoire that may be consistent with strength/resistance physiology having elevated cytoskeletal gene component expression and glycogen metabolism cycling along with higher PI3K levels. In many respects small vs. large fish match eccentric vs. concentric muscle expression patterns, respectively. Lipid metabolic genes are also more elevated in larger fish, the most notable being the G0S2 switch gene. M and Z-line sarcomere remodelling appears to be more prevalent in large fish. Twenty-three out of 26 gene families with previously reported significant SNP-based growth differences were detected as having significant expression differences.
  
  
  CONCLUSIONS
  Larger fish display a broader array of genes showing higher expression, and their profiles are more similar to those observed in December lot fish (i.e., an accelerated growth period). Conversely, small fish display gene profiles more similar to seasonal growth decline phases (i.e., September lot fish). Overall, seasonal timing was coupled to greater differences in gene expression compared to differences associated with fish size.
authors.affiliation: Department of Integrative Biology, University of Guelph, 50 Stone Road East, Guelph, ON, N1G 2W1, Canada. rdanzman@uoguelph.ca.
authors.forename: Roy G
authors.initials: RG
authors.lastname: Danzmann
authors.affiliation: Department of Integrative Biology, University of Guelph, 50 Stone Road East, Guelph, ON, N1G 2W1, Canada. akocmare@uoguelph.ca.
authors.forename: Andrea L
authors.initials: AL
authors.lastname: Kocmarek
authors.affiliation: Department of Integrative Biology, University of Guelph, 50 Stone Road East, Guelph, ON, N1G 2W1, Canada. jnorman@uoguelph.ca.
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Norman
authors.affiliation: National Center for Cool and Cold Water Aquaculture, ARS-USDA, 11861 Leetown Road, Kearneysville, WV, 25430, USA. Caird.RexroadIII@ars.usda.gov.
authors.forename: Caird E
authors.initials: CE
authors.lastname: Rexroad
authors.affiliation: National Center for Cool and Cold Water Aquaculture, ARS-USDA, 11861 Leetown Road, Kearneysville, WV, 25430, USA. Yniv.Palti@ars.usda.gov.
authors.forename: Yniv
authors.initials: Y
authors.lastname: Palti
mesh_terms: D000818:Animals; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D017686:Oncorhynchus mykiss / Q000235:genetics* / Q000254:growth & development; D019869:Phosphatidylinositol 3-Kinases / Q000096:biosynthesis; D012621:Seasons; D058570:TOR Serine-Threonine Kinases / Q000096:biosynthesis; D013696:Temperature; D059467:Transcriptome / Q000235:genetics*; D000077005:Tuberous Sclerosis Complex 2 Protein; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis
chemical_list: D019869:Phosphatidylinositol 3-Kinases; D058570:TOR Serine-Threonine Kinases; D000077005:Tuberous Sclerosis Complex 2 Protein; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; C000624653:TSC2 protein, human