Global gene expression profile during low temperature in the brain of grass carp (Ctenopharyngodon idellus)

Grass carp is an important commercial fish widely cultured in China. Large range of temperature, in particular extremely low temperature, has dramatic effects on the aquaculture of this teleost. However, there is relatively little research on the molecular responses in the fish exposed to cold. Given the limited vision of approaches targeting individual genes, we investigated the transcriptome profiles of brain in response to cold in order to comprehensively characterize molecular mechanisms behind it. This study indicated that the estrogen signaling pathway was inhibited in brain when grass carp acclimated to low temperature, while terpenoid backbone biosynthesis pathway and steroid biosynthesis pathway were significantly activated. Such a result implied the crucial role of cholesterol in cold acclimation. Moreover, plenty of differentially expressed genes associated with spliceosomes were enriched during cooling process, which suggested alternative splicing may be involved in the regulation of biological process in acclimation to temperature changes. In researches on extremely low-temperature tolerance, we identified four genes (DUSP1, HSPA6, NR4A1 and GADD45B) associated with MAPK signaling pathway. The four genes, extensively up-regulated at 4{degrees}C and remained relatively low expression at moderate temperature, were closely related with extremely cold condition. Further examination of the candidate genes can provide insights into the mechanisms of grass carp to endure extremely low temperature in the winter.