Abstract
BackgroundOsmotic stress is a widespread phenomenon in aquatic animal. The ability to cope with salinity stress and alkaline stress is quite important for the survival of aquatic species under natural conditions. Tilapia is an important commercial euryhaline fish species. What’s more tilapia is a good experimental material for osmotic stress regulation research, but the molecular regulation mechanism underlying different osmotic pressure of tilapia is still unexplored.ResultsTo elucidate the osmoregulation strategy behind its hyper salinity, alkalinity and salinity-alkalinity stress of tilapia, the transcriptomes of gills in hybrid tilapia (Oreochromis mossambicus ♀ × O. urolepis hornorum ♂) under salinity stress (S: 25‰), alkalinity stress(A: 4‰) and salinity-alkalinity stress (SA: S: 15‰, A: 4‰) were sequenced using deep-sequencing platform Illumina/HiSeq-2000 and differential expression genes (DEGs) were identified. A total of 1958, 1472 and 1315 upregulated and 1824, 1940 and 1735 downregulated genes (P-value < 0.05) were identified in the salt stress, alkali stress and saline-alkali stress groups, respectively, compared with those in the control group. Furthermore, Kyoto Encyclopedia of Genes and Genomes pathway analyses were conducted in the significant different expression genes. In all significant DEGs, some of the typical genes involved in osmoregulation, including carbonic anhydrase (CA), calcium/calmodulin-dependent protein kinase (CaM kinase) II (CAMK2), aquaporin-1(AQP1), sodium bicarbonate cotransporter (SLC4A4/NBC1), chloride channel 2(CLCN2), sodium/potassium/chloride transporter (SLC12A2 / NKCC1) and other osmoregulation genes were also identified. RNA-seq results were validated with quantitative real-time PCR (qPCR), the 17 random selected genes showed a consistent direction in both RNA-Seq and qPCR analysis, demonstrated that the results of RNA-seq were reliable.ConclusionsThe present results would be helpful to elucidate the osmoregulation mechanism of aquatic animals adapting to saline-alkali challenge. This study provides a global overview of gene expression patterns and pathways that related to osmoregulation in hybrid tilapia, and could contribute to a better understanding of the molecular regulation mechanism in different osmotic stresses.
Highlights
IntroductionThe ability to cope with salinity stress and alkaline stress is quite important for the survival of aquatic species under natural conditions
Osmotic stress is a widespread phenomenon in aquatic animal
Sequencing and the analysis of reads To identify mRNAs in hybrid tilapia in response to osmotic stress challenges, mRNA libraries derived from 12 groups were constructed and sequenced using the Illumina deep-sequencing platform
Summary
The ability to cope with salinity stress and alkaline stress is quite important for the survival of aquatic species under natural conditions. Salinity has been long recognized as one of the fundamental factors affecting aquatic species distribution and influencing physiological processes of marine and estuarine organisms, such as survival, hemolymph osmolarity, and tissue water content [1,2,3]. Carbonate alkalinity stress was considered as a major risk factor for fishes surviving in saline-alkaline water [6, 7]. Many studies have examined osmoregulatory physiology in freshwater and marine populations of fish [8,9,10,11,12], it still remains unknown about the molecular mechanism of osmotic stress tolerance [13]. The identification and characterization of the genes and the regulatory factors involved in hyperosmoregulation are essential for increasing the production and the efficiency of selective breeding programs for some important fish species
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