Photoperiod regulation of molecular clocks and seasonal physiology in the Atlantic salmon (Salmo salar)

• Main Author: McStay, Elsbeth
• Other Authors: Migaud, Herve, Davie, Andrew
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Stirling 2012
• Subjects: Photoperiod; Clocks; Seasonal; Circadian; Atlantic salmon; Photoperiodism; Salmo salar
• Online Access: http://hdl.handle.net/1893/11012; http://dspace.stir.ac.uk/bitstream/1893/11012/1/E.Mcstay%20final%20PhD.pdf

Recent years have seen considerable advances in the study of biological rhythms and the underlying molecular mechanisms that drive the daily and seasonal physiology of vertebrates. Amongst teleosts the majority of work in this field has focused on the model species the zebrafish to characterise clock genes and the molecular feedback loop that underpins circadian rhythms and physiology. Daily profiles of clock gene expression in a wide variety of tissues and cell types are now relatively well described. However the zebrafish is a tropical species that does not display distinct seasonality and therefore may not be the species of choice to investigate the entrainment of circannual physiology. In contrast, Atlantic salmon is a highly seasonal teleost that displays considerable temporal organisation of most physiological processes. In salmonids photoperiod is widely known to synchronise physiology to the environmental conditions and as such photoperiod manipulation is routinely used by the salmon industry throughout the production cycle to control and manipulate spawning, smoltification and puberty. Previous studies in salmonid species have already identified a set of clock genes that are linked to these seasonal physiological processes. However, to date, the molecular mechanisms regulating daily and seasonal physiology are largely unknown despite the strong commercial relevance in the Atlantic salmon. In the Atlantic salmon, Davie et al (2009) was the first to report the photoperiod dependent circadian expression of clock genes (Clock, Bmal and Per2 and Cry2) in the brain of the Atlantic salmon. In the same investigation the expression of clock genes was reported in a wide variety of peripheral tissues, however 24h profiles of expression in peripheral tissues were not characterised. In order to examine further the role of seasonal photoperiod on the circadian expression of clock genes, the present work first aimed to characterise diel profiles of Clock, Per1 and Per 2 expression in the brain together with plasma ...