title: Phytotoxicity, bioaccumulation and degradation of isoproturon in green algae.
abstract: Isoproturon (IPU) is a pesticide used for protection of land crops from weed or pathogen attack. Recent survey shows that IPU has been detected as a contaminant in aquatic systems and may have negative impact on aquatic organisms. To understand the phytotoxicity and potential accumulation and degradation of IPU in algae, a comprehensive study was performed with the green alga Chlamydomonas reinhardtii. Algae exposed to 5-50 μg L(-1) IPU for 3d displayed progressive inhibition of cell growth and reduced chlorophyll fluorescence. Time-course experiments with 25 μg L(-1) IPU for 6d showed similar growth responses. The 72 h EC50 value for IPU was 43.25 μg L(-1), NOEC was 5 μg L(-1) and LOEC was 15 μg L(-1). Treatment with IPU induced oxidative stress. This was validated by a group of antioxidant enzymes, whose activities were promoted by IPU exposure. The up-regulation of several genes coding for the enzymes confirmed the observation. IPU was shown to be readily accumulated by C. reinhardtii. However, the alga showed a weak ability to degrade IPU accumulated in its cells, which was best presented at the lower concentration (5 μg L(-1)) of IPU in the medium. The imbalance of accumulation and degradation of IPU may be the cause that resulted in the detrimental growth and cellular damage.
authors.affiliation: Jiangsu Key Laboratory of Pesticide Science, College of Science, Nanjing Agricultural University, Nanjing, China.
authors.forename: Yan Fang
authors.initials: YF
authors.lastname: Bi
authors.forename: Shan Shan
authors.initials: SS
authors.lastname: Miao
authors.forename: Yi Chen
authors.initials: YC
authors.lastname: Lu
authors.forename: Chong Bin
authors.initials: CB
authors.lastname: Qiu
authors.forename: You
authors.initials: Y
authors.lastname: Zhou
authors.forename: Hong
authors.initials: H
authors.lastname: Yang
mesh_terms: D001673:Biodegradation, Environmental; D018533:Biomass; D049109:Cell Proliferation / Q000187:drug effects; D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000378:metabolism*; D002734:Chlorophyll / Q000096:biosynthesis; D003470:Culture Media; D005453:Fluorescence; D016166:Free Radical Scavengers / Q000378:metabolism; D005786:Gene Expression Regulation / Q000235:genetics; D006540:Herbicides / Q000378:metabolism* / Q000633:toxicity*; D006861:Hydrogen Peroxide / Q000378:metabolism; D018384:Oxidative Stress; D010671:Phenylurea Compounds / Q000378:metabolism* / Q000633:toxicity*; D060888:Real-Time Polymerase Chain Reaction; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D003470:Culture Media; D016166:Free Radical Scavengers; D006540:Herbicides; D010671:Phenylurea Compounds; D002734:Chlorophyll; C028904:isoproturon; D006861:Hydrogen Peroxide; D013482:Superoxide Dismutase