Gene transcriptional profiling of osmoregulatory stress response in salmonids: Development and assessment of high-throughput multispecies assays.

Osmoregulatory stress is a critical factor in the welfare and performance of salmonids under captive rearing for aquaculture and conservation, and characterizing cellular responses to that stress may foster better husbandry. One approach for early detection of osmotic stress is gene transcriptional profiling, where a suite of qPCR assays designed for related-function genes is used to determine patterns of transcriptional responses to stress. This study describes the development, assessment and application of 28 Taqman qPCR assays for use on the OpenArray® platform as an osmoregulatory stress transcriptional profiling (OSTP) chip. The assays include key genes involved in osmoregulation (twelve), stress response (four), immune function (five), growth/metabolism (four) and endogenous controls (three). Here, using gill and liver tissues from eight salmonid species across four genera, the OSTP chip's performance was evaluated. While results showed both tissue- and species-specific transcriptional differences, the OSTP chip has considerable utility for characterizing molecular stress responses. As a test application of the OSTP chip, we performed a 24-hour saltwater challenge with Chinook salmon and applied the chip to control and challenged fish. This test confirmed the OSTP chip's capacity to detect acute osmotic stress-induced molecular genetic signatures. This OSTP chip will be useful for aquaculture practices by fostering better husbandry as well as providing a valuable tool for future studies of the osmoregulatory response of salmonid fishes to environmental stress.