Salinity‐Induced Gene Expressions in Pangasius nasutus (Bleeker, 1863)

This study was designed to evaluate the molecular responses of Pangasius nasutus to salinity exposure of varying concentrations. Juveniles of P. nasutus from similar breeding history (average size of 35 ± 0.54 cm and 152 ± 1.82 g) were obtained from a known source in Terengganu. The salinity range used for this study (i.e., 0, 10, 15, and 20 ppt) was determined through a range finding test, and the juveniles of P. nasutus were exposed in triplicates to these selected salinity ranges for 2 weeks under laboratory conditions. Thereafter, muscle tissues were collected from 10 biological replicates for molecular analysis. Differential display reverse transcriptase PCR was used to identify the expressed cDNA fragments, while real‐time PCR was used to determine the regulation of selected genes. The results showed that the 14 differentially expressed genes (DEGs) identified were homologous to nine known genes in GenBank. These proteins include fructose biphosphate aldolase A (ALDOA) , troponin I (TnI) , myo sin heavy chain (MYH) , myo sin light chain 1a(MLC 1a) , creatine kinase (CK) , ATPase ii subunit 8 (ATP8) and 6 (ATP6) , parvalbumin(PV) , ribosomal protein L26(RPL26) , and L11 (RPL11) . Real‐time quantitative PCR (qPCR) analysis of TnI , MYH , and PV showed that the highest expression (p  < 0.05) occurred in the 20 ppt salinity treatment group, i.e., 8.79, 3.76, and 1.79 fold more induction than in the control group, respectively. However, the expression of the growth hormone (GH) gene was higher in the 10 ppt salinity treatment than in the control group (p  < 0.05). This study confirmed that salinity exposure induces the expression of several genes in P. nasutus , however, future studies need to unravel the importance of these genes for fish performance.