Transcriptomic response to three osmotic stresses in gills of hybrid tilapia (Oreochromis mossambicus female × O. urolepis hornorum male)

Abstract

Background: Osmotic 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. Results: To 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. Conclusions:The 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.

Slc4 Gene Family in Spotted Sea Bass (Lateolabrax maculatus): Structure, Evolution, and Expression Profiling in Response to Alkalinity Stress and Salinity Changes

“…In agreement with our finding, the functional involvements of slc4a4 in the gills were reported in eel (Anguilla rostrata) [43]. In addition, as the intestinal HCO 3 − secretion is the key mechanism to enable luminal aggregate formation and water absorption, and transepithelial movement of basolateral HCO 3 − is mediated by slc4a4 present in the basolateral membrane, several studies have reported the essential function of Slc4a4 in the intestine of marine fishes like European sea bass (Dicentrarchus labrax), sea bream (Sparus aurata L.), Mozambique tilapia (Oreochromis mossambicus) [13,44,45], and hybrid tilapia (Oreochromis mossambicus female × O. urolepis hornorum male) [46]. In that case, the expression pattern of slc4a4 needs to be investigated in spotted sea bass in a future study.…”

The time course of molecular acclimation to seawater in a euryhaline fish

“…The CSR machinery responds to sodium-destabilized proteins by overexpressing molecular chaperones, such as heat shock proteins (T. G. Evans & Kultz, 2020), two of which were temporarily upregulated in Arabian pupfish at 24 hours, as well as in a hyperosmotic challenged Sacramento splittail population (Mundy et al, 2020). Rising intracellular sodium levels can also cause nucleic acid structural disruptions (T. G. Evans & Kultz, 2020), and consequently, increased expressions of DNA damage related genes are often reported as part of the CSR following hyperosmotic stress in teleosts (Brennan et al, 2015;Su, Ma, Zhu, Liu, & Gao, 2020;Whitehead et al, 2013). In Arabian pupfish several DNA damage related genes were transiently upregulated especially in the first 24 hours of exposure, like serum/glucocorticoid regulated kinase 1 (SGK1), and similarly increased in other fish following acute seawater challenges (T. G. Evans & Somero, 2008;Shaw et al, 2008).…”

Transcriptional regulation ofprolactinin a euryhaline teleost: Characterisation of gene promoters through in silico and transcriptome analyses

“…In a broader sense, transcriptome analyses in teleost fishes continue to facilitate the identification of novel genes involved in osmoregulation. [58][59][60][61][62][63] In the mammalian kidney, a functional hyperosmotic cis-response element was identified in cells of the renal medulla exposed to dramatic changes in extracellular osmolality. 64 This osmotic-response element (ORE), also called tonicity-responsive enhancer, regulates genes involved in the accumulation of compatible osmolytes (i.e.…”

“…hypo‐ vs hyperosmotic extracellular conditions). In a broader sense, transcriptome analyses in teleost fishes continue to facilitate the identification of novel genes involved in osmoregulation 58‐63 …”