Study Of Toxicity Effects And Molecular Biomarkers Of Clam Venerupis Philippinarum Exposed To Endosulfan

Endosulfan （EDS） is an organochlorine （OC） compound that has been classifiedas highly toxic by the majority of environmental protection agencies. In present study,the acute toxicity and sub-chronic toxic effects of endosulfan on clam Venerupisphilippinarum were studied from enzymology and molecular level. The subtractivecDNA library of Venerupis philippinarum exposed to endosulfan was constructed bysuppression subtractive hybridisation （SSH） and differentially expressed genes wereidentified. The resulting data may provide reference for endosulfan toxicity effectstudy especially the toxicity research on aquatic invertebrates. Studies on theconstruction of subtractive cDNA library and the differentially expressed genes mayprovide basic genomic information of the bivalve and molecular biomarkers whichmay be selected to monitor the endosulfan pollution in aquatic environment.1The toxicity effect research of Venerupis philippinarum exposed toEndosulfanWe studied the toxicity effects of clam Venerupis philippinarum exposed toendosulfan in this research. Study of the acute toxicity showed that there was no acutetoxicity to the clam V. philippinarum.Besides, another study is aimed at evaluating the effects of endosulfan in clamsVenerupis philippinarum. For this purpose, a study was performed on clams exposedto0.005,0.05and0.5μg/L endosulfan for15days. Subsequently, the level ofethoxyresorufin-O-deethylase （EROD） activity, glutathione-S-transferase （GST）activity, glutathione （GSH） content, superoxide dismutase （SOD） activity, lipidperoxidation （LPO） and DNA strand break were determined in gills and digestiveglands. Among the parameters, endosulfan caused significant changes in induction ofEROD activity and oxidative stress in clams Venerupis philippinarum. Moreover,according to the correlation analysis results, the EROD activity and GSH content in digestive gland as well as GST activity, LPO and DNA damage in both tissues hadexcellent correlation with endosulfan concentration. These results providedinformation on potential biomarkers that could be effectively applied to thebiomonitoring of aquatic ecosystem in areas susceptible to persistent organochlorinecompounds contamination, and also information on toxic effects.2Screening and analysis of differential expressed genes of Venerupisphilippinarum exposed to EndosulfanForward and reverse subtracted cDNA library of Venerupis philippinarumexposed to0.5μg/L endosulfan for1d and10d were constructed by suppressionsubtractive hybridization （SSH）. According to the results of sequencing analysis,fifty-six and forty unigenes were identified from1d and10d forward cDNA libraryrespectively; fifty and seventy-two unigenes were identified from1d and10d reversecDNA library respectively. The cDNA library accession number of the clam isLIBEST₀27859and with GenBank accession no. JK845831–JK845901of partialESTs. The functional annotation results show that up and down regulated genesduring exposure to endosulfan are associated with the follow major physiologicalfunctions: i translation; ii posttranslational modification; iii energy production andconversion; iv detoxification metabolism; vi immune response; vii metabolism; viiigeneral function prediction only. To validate the expression profiles from SSH, somegenes regulated by endosulfan were measured by quantitative real time PCR. Resultsshowed that mRNA expression of several genes including Cathepsin L2、Aminesulfotransferase（SULT）、AChE and Hydroxysteroid （17-beta） dehydrogenase wereup-regulated by endosulfan exposure, which indicated that these genes were suitablemolecular biomarkers of clam for endosulfan assessment. This study providesinformation for the characterization of potential molecular biomarker that may beused in future environmental monitoring and to investigate the mechanisms of stressto endosulfan in clams/marine invertebrates.