Transcriptomic analysis reveals putative osmoregulation mechanisms in the kidney of euryhaline turbot Scophthalmus maximus responded to hypo-saline seawater

Turbot harbor a relatively remarkable ability to adapt to opposing osmotic challenges and are an excellent model species to study the physiological adaptations of flounder associated with osmoregulatory plasticity.The kidney transcriptome of turbot treated 24 h in water of hypo-salinity(salinity 5)and seawater(salinity 30)was sequenced and characterized.In silico analysis indicated that all unigenes had significant hits in seven databases.The functional annotation analysis of the transcriptome showed that the immune system and biological processes associated with digestion,absorption,and metabolism played an important role in the osmoregulation of turbot in response to hypo-salinity.Analysis of biological processes associated with inorganic channels and transporters indicated that mineral absorption and bile secretion contributed to iono-osmoregulation resulting in cell volume regulation and cell phenotypic plasticity.Moreover,we analyzed and predicted the mechanisms of canonical signaling transduction.Biological processes involved in renin secretion,ECM-receptor interaction,adherens junction,and focal adhesion played an important role in the plasticity phenotype in hypo-stress,while the signal transduction network composed of the MAPK signaling pathway and PI3K-Akt signaling pathway with GABAergic synapse,worked in hypoosmoregulation signal transduction in the turbot.In addition,analysis of the tissue specificity of targeted gene expression using qPCR during salinity stress was carried out.The results showed that the kidney,gill,and spleen were vital regulating organs of osmotic pressure,and the osmoregulation pattern of euryhaline fish dif fered among species.

Validation of Housekeeping Genes for Gene Expression Analysis in Iwagaki Oyster(Crassostrea nippona)Under Salinity Stress by Quantitative Real-Time PCR

Hypo-salinity can reduce the immunological reaction in Crassostrea nippona,even lead to massive mortality.It is important to understand the molecular mechanism of oyster defense system,while quantitative real-time PCR can be employed in the study.However,the accuracy of quantitative real-time PCR relies on the use of suitable reference genes.In this study,the expression stability of 14 candidate reference genes including traditional housekeeping genes EF1A,TUB,TUA,GAPDH,RO21,as well as new candidate reference genes RPL5,RPL8,RPS27,RPL14,RPL4,CO3,RPS8,RPS4,CYTB in different tissues of C.nippona under salinity stress has been validated by quantitative real-time PCR.Ribosomal protein genes selected through expression analysis of transcriptome data from C.nippona generally were more stable than traditional reference genes.According to the geNorm analysis,RPL4 and RPS4 could be used as internal controls for studying gene expression in C.nippona with real-time PCR under salinity stress.