Heat shock proteins 70 (HSP70s) are known to play essential roles in organisms’ response mechanisms to various environmental stresses. However, no systematic identification and functional analysis has been conducted for HSP70s in the turbot (Scophthalmus maximus), a commercially important worldwide flatfish. Herein, 16 HSP70 genes unevenly distributed on nine chromosomes were identified in the turbot at the genome-wide level. Analyses of gene structure, motif composition, and phylogenetic relationships provided valuable data on the HSP70s regarding their evolution, classification, and functional diversity. Expression profiles of the HSP70 genes under five different stresses were investigated by examining multiple RNA-seq datasets. Results showed that 10, 6, 8, 10, and 9 HSP70 genes showed significantly up- or downregulated expression after heat-induced, salinity-induced, and Enteromyxum scophthalmi, Vibrio anguillarum, and Megalocytivirus infection-induced stress, respectively. Among them, hsp70 (hspa1a), hspa1b, and hspa5 showed significant responses to each kind of induced stress, and qPCR analyses further validated their involvement in comprehensive anti-stress, indicating their involvement in organisms’ anti-stress mechanisms. These findings not only provide new insights into the biological function of HSP70s in turbot adapting to various environmental stresses, but also contribute to the development of molecular-based selective breeding programs for the production of stress-resistant turbot strains in the aquaculture industry.

The mitogen-activated protein kinase (MAPK) gene family performs crucial roles in cell division, migration, development, apoptosis, inflammatory response, and abiotic and biotic stress responses. However, very little information is available about the MAPKs in turbot (Scophthalmus maximus). In this study, 15 turbot MAPKs (SmMAPKs) were identified throughout the whole genome, and their basic chemical and physical properties and subcellular localization were illustrated. All SmMAPKs contained the serine/threonine protein kinases, catalytic domain (S_TKc, SMART00220). Phylogenetic analysis revealed that SmMAPKs were classified into three subfamilies, namely, c-Jun NH2-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), and p38. Conserved motif and gene structure analysis revealed high levels of conservation within and between phylogenetic subfamilies. Expression patterns of MAPKs in distinct tissues and under diverse abiotic and biotic stresses were examined using the published available RNA-seq data sets. As a result, SmMAPKs showed obviously tissue-specific expression. Furthermore, 7 and 10 candidate stress-responsive MAPK genes were detected under abiotic and biotic stresses, respectively, among which five common MAPK genes, namely, SmMAPK4 (ERK4), SmMAPK6 (ERK3), SmMAPK11 (p38β), SmMAPK12b (p38γ), and SmMAPK15 (ERK7/8) showed extremely significant responses to both abiotic and biotic stresses, demonstrating their potential functions in comprehensive antistress. These results demonstrate that MAPKs might play vital roles in response to various abiotic and biotic stresses in turbot, which would contribute to making scientific preventive measures to environmental changes in the process of farming and promoting the development of selective breeding for comprehensive stress resistance in turbot.