Study On The Mechanism Of Meretrix Meretrix Response To Cd²⁺ Exposure Based On Transcriptome Analysis

With the rapid development of industry,China's local coastal waters pollution is very serious,which is a serious threat to the marine ecological environment.The heavy metal pollution has become a hotspot of marine pollutants because of its long duration,biodegradability and relative stability.Studies have shown that very low levels of heavy metal contaminants have a very serious negative effect on shellfish.By investigating the heavy metal content in sediments in the Liaohe Estuary,it was found that the concentration of heavy metals in the sediments was Cr?49.04 mg/kg?> Cu?14.94 mg/kg?> Pb?12.86 mg/kg?> As?6.54 mg/kg?> Cd?0.175 mg/kg?> Hg?0.039 mg/kg?.The contamination factor?CF?,the geoaccumulation index and the potential ecological risk index were used to analyze the pollution situation,which showed that the heavy metal pollution in Liaohe Estuary is mainly dominatedby Cd.In order to reveal the physiological complement mechanism of bivalve molluscs under heavy metal stress,this study examined the differential expression of functional genes of Meretrix meretrix under Cd stress to understand the response mechanism of Meretrix meretrix to Cd stress.The Hi-seq 2500 of Illumina platform was used to sequence the mRNA transcriptome of the gill,finding the function genes response to the Cd²⁺ exposure and verified by QRT-PCR.The results shows a total of 99,658 transcripts and 50,866 unigenes were obtained from 35.2 million filtered reads and 20,096 unigenes were annotated by hitting against NCBI database.Six functional genes with obvious response to Cd²⁺ were identified.The results of real-time quantitative PCR showed that the expression of cytochrome P450?CYP450?,glutathione peroxidase A?GPA?and glutathionase-transferase?GST?were similar,which were inhibited in the low concentration of Cd²⁺stimulation,but induced in the high concentration of Cd²⁺ stimulation.The expression of heat shock protein 70?Hsp70?gene was significantly increased and then returned back until it remained stableunder the stimulation of the two treatment groups.The expression of catalase?CAT?was induced when exposed to the two treatment groups.The expression of Cu/Zn superoxide dismutase gene?Cu/Zn SOD?was inhibited when exposed to the two treatment groups.The changes in the expression of these genes indicate that these six genes are related to the response of the clam to environmental stress,and this method can be used to further study the methods of protecting the clonal germplasm resources.