Quantitative label‐free proteomics of tilapia gill epithelium: confirmation of established and identification of novel responses to salinity change (1182.4)

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Label‐free quantitative (LFQ) proteomics was employed to analyze effects of salinity stress on the molecular phenotype, i.e. proteome, of gill epithelium in Mozambique tilapia (Oreochromis mossambicus). Fresh water (FW) acclimated tilapia were acclimated to 34 ppt, 70 ppt, and 90 ppt salinity and gill proteins extracted and trypsin‐digested for analysis by LFQ LC‐MS/MS. More than 600 proteins were identified with high identification scores (>85% represented by >5 MS/MS peptides, FDR < 2%). The overall effect of salinity acclimation on protein regulation ratios in gill epithelium (salinity exposed gill epithelia compared to FW handling controls) was found to be proportional to the degree of salinity stress. Salinity‐induced changes in tilapia gill epithelial proteome directly reflected known salinity effects on gills of euryhaline fish, including an increase in the size and number of mitochondria‐rich ionocytes, activities of specific ion transporters, and induction of specific molecular chaperones. Confirming such known effects of salinity on tilapia gill epithelium at the proteome level validated the LFQ workflow. In addition to confirming known salinity stress responses, novel gill proteins involved in salinity acclimation of tilapia, notably protein NDRG1, were identified by this workflow. We propose that protein NDRG1 participates in gill epithelial remodeling during salinity acclimation of euryhaline fish. Moreover, we conclude that LFQ proteomics represents a powerful tool for gaining deep insight into effects of environmental salinity stress on the molecular phenotype of osmoregulatory tissues in euryhaline fish. Supported by NSF grant IOS‐1049780.Grant Funding Source: NSF IOS‐1049780