Digital RNA-seq analysis of the cardiac transcriptome response to thermal stress in turbot Scophthalmus maximus.

The hearts of fish play a major role in their physiological plasticity and acclimation to different thermal conditions. To understand the precise mechanism and the pathways activated by thermal cardiac stress in fish, we sampled cardiac tissue from juvenile turbot (Scophthalmus maximus) exposed to control (14°C) and test (20°C, 24°C, and 28°C) conditions, and performed digital RNA sequencing (RNA-seq). A total of 3359 differentially expressed genes (DEGs) were identified. The results of an expression tendency analysis and KEGG annotation analysis of the DEGs demonstrated that energy metabolism played a core role in thermal stress in turbot for the majority of the up-regulated genes. This was followed by lipid metabolism, mitochondrial function, glycolysis, and carbohydrate metabolism. RNA modifications are gaining the interest of biologists worldwide. In this study, at the transcriptome level, our results showed that 246 m6A-containing genes were detected in the DEGs, which were related to EIF3C, EIF3D, EIF3J, METTL16, RBM15B, VIRMA, and YTHDC1. This indicates that mA is involved in the regulation of heat stress in turbot. This study is an important step towards understanding the cardiac adaptive response to thermal stress. Importantly, the plasticity of cardiac tissue could predict the adaptability of fish species to environmental temperature.