Identification of mapk gene family in Lateolabrax maculatus and their expression profiles in response to hypoxia and salinity challenges

Mitogen-activated protein kinases (MAPK) superfamily exerts crucial roles in the regulation of intracellular metabolism, gene expression as well as integral activities in diverse cellular processes. In our study, 14 mapk genes were identified in spotted sea bass (Lateolabrax maculatus) and these genes were divided into three subfamilies according to phylogenetic analysis, including 6 erk genes, 3 jnk genes and 5 p38-mapk genes. Syntenic and tertiary structure analysis confirmed their annotation and orthologies. The expression profiles of several stress-responsive mapk genes of spotted sea bass were examined in gill using quantitative real-time PCR after salinity (0 parts per thousand, 12 parts per thousand, 30 parts per thousand, 45 parts per thousand) and hypoxia challenges (DO = 1.0 +/- 0.2 mg/L). After salinity challenge, significant up-regulations were observed in the expressions of mapk8 (jnkl), mapk9 (jnk2), mapk11 (p3813), mapkl4a (p38a) and mapkl4b (p38b). mapk8 and mapk9 were more sensitive to hypotonic challenge (0 parts per thousand) than hyperosmotic (45 parts per thousand) and isosmotic challenges (12 parts per thousand), while the highest expression of mapk11, mapkl4a and mapkl4b were observed in hyperosmotic challenge (45 parts per thousand). After hypoxia challenge, the expression levels of mapkl (erk2), mapk3 (erkl) and mapkl4a (p38a) in treatment group (DO = 1.0 +/- 0.2 mg/L) were significantly up-regulated in comparison with control group (DO = 8.0 +/- 0.5 mg/L) in time-dependent manner. These results indicated that these mapk genes in spotted sea bass may play important roles in response to salinity and hypoxia challenges.