| Cadmium(Cd)is a common heavy metal pollutant that cannot be biodegraded in the environment.When the environment is contaminated with cadmium,cadmium will accumulate in the organisms and enter the human body through the food chain,causing potential harm and affecting human health.Procambarus clarkii is commonly known as crayfish.It has a strong ability to enrich heavy metals such as cadmium,and can survive and reproduce in heavy metal contaminated environments.Keeping harmful pollutants out of some crucial tissues as much as possible is a key trait for the organism to survive in adverse environments such as heavy metal contaminated aquatic environments.It is known from the previous literatures that the p38 MAPK gene may play an important role in the response of organisms to environmental stress.So it was hypothesized that the p38 Mitogen-activated Protein Kinase(MAPK)controls the distribution of cadmium in crayfish by regulating the accumulation of cadmium in different tissues under Cd-stressed conditions,in order to maintain the normal life activities of the crayfish.Therefore,it is valuable and significant to study the cadmium accumulation and p38 gene expression in Procambarus clarkii.In this paper,the cadmium accumulation in gill,hepatopancreas and muscle of Procambarus clarkii under different concentrations of cadmium were studied at first.Then in order to verify the hypothesis that the p38 MAPK of Procambarus clarkii can regulate the accumulation and distribution of cadmium in its different tissues,the cloning and sequence analysis of the p38 MAPK were studied,the distribution of p38 gene and cadmium content in the tissues of Procambarus clarkii were detected,the p38 gene expression and cadmium content in different tissues at different times under cadmium exposure were analyzed and compared in this article.The results showed that the Procambarus clarkii p38 MAPK gene consists of an open reading frame of 1098 bp encoding 365 amino acids,it had the highest homology with Macrobrachium nipponense and Palaemon carinicauda,with a similarity of 95%.The p38 MAPK is tissue-specific expression in all tested tissues under no stress,the expression level was the lowest in hepatopancreas.Under cadmium stress,the expression level of p38 gene in different tissues varies with time.There are some differences among them,the expression of p38 gene in the heart,antennal gland,gill and muscle shows an overall upward trend in the early stage and a downward trend in the later stage,and have volatility and reciprocity.Compared with the control group,the expression of p38 had up-regulation and down-regulation.For hepatopancreas,p38 expression fluctuated with time under cadmium exposure,but the expression level was always lower than that in the control group.The cadmium accumulation in different tissues increased with the increase of exposure time.The cadmium content in hepatopancreas was much higher than that in the heart,antennal gland and muscle tissues,while its p38 expression was always lower than other tissues.These results indicate that the Procambarus clarkii p38 MAPK plays an important role in regulating the accumulation and distribution of cadmium in different tissues.The low expression of this gene in hepatopancreas,it makes this tissue become the main tissue for the cadmium accumulation,making cadmium accumulate as little as possible in other key tissues,in order to reduce the overall harm to the Procambarus clarkii,to maintain its survival and life activities in a cadmium-contaminated environment. |
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