Molecular characterization of p38 MAPK and tissue-specific expression under cadmium stress in red swamp crayfish...

Keeping harmful pollutants out of some crucial tissues as much as possible is a key trait for the organism to survive in adverse conditions, such as in heavy-metal contaminated aquatic environments. In the current study, it was hypothesized that the p38 Mitogen-activated Protein Kinase (MAPK) controls the distribution of cadmium (Cd) in red swamp crayfish (Procambarus clarkii) by regulating the accumulation of Cd in different tissues under Cd-stressed conditions. To test this hypothesis, this study analyzed the p38 MAPK gene and compared the differential expression levels in the heart, antennal gland, gill, hepatopancreas, and muscles. Differences in expression levels of p38 MAPK gene between different tissues were conducted under controlled Cd exposure. This study found that the expression of p38 MAPK is tissue-specific in all tested samples under non-stressed condition. Under Cd-stressed condition and with the prolongation of Cd exposure time, the content of Cd in all examined tissues of P. clarkii has substantially increased compared to the control, although the Cd contents in the heart, antennal gland, and muscle remained relatively lower than those observed in the hepatopancreas. Consequently, the levels of p38 MAPK in the heart, antennal gland, and muscle were higher than the level in the hepatopancreas. These results indicate that p38 MAPK regulates the distribution and accumulation of Cd in different tissues of P. clarkii under Cd-stressed condition. Furthermore, the results suggested that the higher expression of p38 MAPK played a crucial role in keeping Cd out of the tissues in the Cd-rich aquatic environment to maintain the normal physiological function of the red swamp crayfish, a process necessary for survival and growth.