RNA-seq reveals temporal differences in the transcriptome response to acute heat stress in the Atlantic salmon (Salmo salar).

Acute heat stress is common in aquaculture and can affect diverse physiological processes in fish; however, different species of fish have various mechanisms for heat stress adaptation. In this study, we profiled the transcriptome responses of the Atlantic salmon (Salmo salar) to heat stress at 23 °C for 6 or 24 h, compared with that of fish at a normal temperature of 13 °C. The liver was selected as the target tissue for this analysis. A total of 243 and 88 genes were differentially expressed after 6 and 24 h of heat stress, respectively. Of these, only 22 were common to both time points, and most of these common genes were molecular chaperones such as heat shock cognate 71 kDa protein and heat shock protein 90-alpha. Genes such as activating transcription factor 6, calreticulin, protein disulfide isomerase A3, and protein kinase R-like endoplasmic reticulum kinase-eukaryotic initiation factor 2-alpha were only up-regulated after 6 h of heat stress; most of these genes are involved in the endoplasmic reticulum stress pathway. Indeed, endoplasmic reticulum stress was identified at 6 h but not at 24 h, suggesting that stress response plays an important role in the adaptation of Atlantic salmon to acute heat stress. Other up-regulated genes at 6 h were related to the insulin and nucleotide oligomerization domain-like receptor signaling pathways, which directly eliminate misfolded proteins and sustain sugar and lipid homeostasis. At 24 h, heat stress influenced the expression of steroid and terpenoid backbone biosynthesis, which may influence the sexual development and differentiation of Atlantic salmon. Overall, our results elucidate the transcriptome mechanisms that contribute to short-term heat tolerance in the liver of Atlantic salmon.

[Antioxidant responses of rainbow trout with different ploidies to acute temperature stress.] / 不同倍性虹鳟幼鱼对急性温度胁迫的抗氧化响应.

Rainbow trout (Oncorhynchus mykiss) is a cold-water fish species with optimal temperature of 12-18 ℃. Temperature stress is a common issue in commercial culture of the Salmonid fish in summer. Both maple trout and steelhead trout are rainbow trout breeding species with good quality. The purpose of this study was to explore the impact of acute temperature stress on antioxidant responses of two kinds of rainbow trout. The juvenile maple trout was diploid, and the juvenile steelhead trout was triploid. The fishes were exposed to four different temperature treatments: 13, 17, 21, and 25 ℃, and hepatic samples were collected at 0, 1, 6, and 12 h. After acute heat stress, the fish were transferred to the tank with optimal temperature (13 ℃) and hepatic samples were collected after 1, 12, 24, and 48 h. The biomarkers, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), lipid peroxidation (LPO), malondialdehyde (MDA), and heat shock protein 70 kDa (HSP70) were measured. Results showed that the activities of SOD, CAT, and GPx in both maple trout and steelhead trout in 17 ℃ treatment had no significant increase after acute temperature stress. The SOD activities of maple trout and steelhead trout in 21 ℃ treatment significantly increased in response to acute temperature stress, but the SOD activity of maple trout returned to normal during the recovery process. The activities of SOD, CAT, and GPx for both species in 25 ℃ treatment were significantly increased after acute temperature stress, which returned to normal for 24 h recovery. The amount of HSP70 produced by maple trout at 17, 21, and 25 ℃ treatments was significantly higher than that at 13 ℃ treatment, while that of steelhead trout was significantly higher for the 21 and 25 ℃ treatments than that at 13 ℃ treatment. A variety of antioxidant parameters were analyzed by integrated biomarker response (IBR) values. Results showed that the antioxidant response of maple trout was significantly higher than that of steelhead trout in 17 ℃ and 21 ℃ treatments, but significantly lower than steelhead trout in 25 ℃ treatment. Such a result indicated that the antioxidant responses of different ploidy rainbow trouts were different under acute stress at different temperatures.