Abstract
BackgroundSalinity is an important abiotic stress that influences the physiological and metabolic activity, reproduction, growth and development of marine fish. It has been suggested that half-smooth tongue sole (Cynoglossus semilaevis), a euryhaline fish species, uses a large amount of energy to maintain osmotic pressure balance when exposed to fluctuations in salinity. To delineate the molecular response of C. semilaevis to different levels of salinity, we performed RNA-seq analysis of the liver to identify the genes and molecular and biological processes involved in responding to salinity changes.ResultsThe present study yielded 330.4 million clean reads, of which 83.9% were successfully mapped to the reference genome of C. semilaevis. One hundred twenty-eight differentially expressed genes (DEGs), including 43 up-regulated genes and 85 down-regulated genes, were identified. These DEGs were highly represented in metabolic pathways, steroid biosynthesis, terpenoid backbone biosynthesis, butanoate metabolism, glycerolipid metabolism and the 2-oxocarboxylic acid metabolism pathway. In addition, genes involved in metabolism, osmoregulation and ion transport, signal transduction, immune response and stress response, and cytoskeleton remodeling were affected during acclimation to low salinity. Genes acat2, fdps, hmgcr, hmgcs1, mvk, pmvk, ebp, lss, dhcr7, and dhcr24 were up-regulated and abat, ddc, acy1 were down-regulated in metabolic pathways. Genes aqp10 and slc6a6 were down-regulated in osmoregulation and ion transport. Genes abat, fdps, hmgcs1, mvk, pmvk and dhcr7 were first reported to be associated with salinity adaptation in teleosts.ConclusionsOur results revealed that metabolic pathways, especially lipid metabolism were important for salinity adaptation. The candidate genes identified from this study provide a basis for further studies to investigate the molecular mechanism of salinity adaptation and transcriptional plasticity in marine fish.
Highlights
Salinity is an important abiotic stress that influences the physiological and metabolic activity, reproduction, growth and development of marine fish
More than 94% of bases had a base accuracy of 99% and more than 89% of bases had a base accuracy of 99.9%
These clean reads were mapped against the annotated genome of the half-smooth tongue sole
Summary
Salinity is an important abiotic stress that influences the physiological and metabolic activity, reproduction, growth and development of marine fish. It has been suggested that half-smooth tongue sole (Cynoglossus semilaevis), a euryhaline fish species, uses a large amount of energy to maintain osmotic pressure balance when exposed to fluctuations in salinity. Fluctuations in salinity have a significant impact on fish reproduction, growth, development, and physiological and metabolic activities [2]. Euryhaline fish species can adapt to a wide range of salinities and cope with both chronic and Osmoregulation is one of the most energetically costly metabolic activities in teleosts [6]. The liver participates in certain important physiological processes such as antioxidant activity, glycogen synthesis and bile secretion in teleost fish. Compared with the widely studied osmoregulatory organs such as the gills, kidney and intestine, the liver response to osmotic stress is hardly known in teleosts [2, 9]
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