Rhythmic Clock Gene Expression in Atlantic Salmon Parr Brain

• Published in: Frontiers in Physiology
• Main Authors: Charlotte M. Bolton, Michaël Bekaert, Mariann Eilertsen, Jon Vidar Helvik, Herve Migaud
• Format: Article in Journal/Newspaper
• Language: English
• Published: Frontiers Media S.A. 2021
• Subjects: clock genes; ohnologs; circadian; whole-genome duplication; rhythmic expression; Physiology; QP1-981; Atlantic salmon
• Online Access: https://doi.org/10.3389/fphys.2021.761109; https://doaj.org/article/683c207488874832bf86121a0295f99b

To better understand the complexity of clock genes in salmonids, a taxon with an additional whole genome duplication, an analysis was performed to identify and classify gene family members (clock, arntl, period, cryptochrome, nr1d, ror, and csnk1). The majority of clock genes, in zebrafish and Northern pike, appeared to be duplicated. In comparison to the 29 clock genes described in zebrafish, 48 clock genes were discovered in salmonid species. There was also evidence of species-specific reciprocal gene losses conserved to the Oncorhynchus sister clade. From the six period genes identified three were highly significantly rhythmic, and circadian in their expression patterns (per1a.1, per1a.2, per1b) and two was significantly rhythmically expressed (per2a, per2b). The transcriptomic study of juvenile Atlantic salmon (parr) brain tissues confirmed gene identification and revealed that there were 2,864 rhythmically expressed genes (p < 0.001), including 1,215 genes with a circadian expression pattern, of which 11 were clock genes. The majority of circadian expressed genes peaked 2 h before and after daylight. These findings provide a foundation for further research into the function of clock genes circadian rhythmicity and the role of an enriched number of clock genes relating to seasonal driven life history in salmonids.