title: Damage to DNA caused by UV-B radiation in the desert cyanobacterium Scytonema javanicum and the effects of exogenous chemicals on the process.
abstract: Radiation with UV-B increased the damage to DNA in Scytonema javanicum, a desert-dwelling soil microorganism, and the level of damage varied with the intensity of UV-B radiation and duration of exposure. Production of reactive oxygen species (ROS) also increased because of the radiation. Different exogenous chemicals (ascorbate acid, ASC; N-acetylcysteine, NAC; glyphosate, GPS; and 2-methyl-4-chlorophenoxyacetic acid, MCPA-Na) differed in their effect on the extent of DNA damage and ROS production: whereas NAC and ASC protected the DNA from damage and resulted in reduced ROS production, the herbicides (GPS and MCPA-Na) increased the extent of damage, lowered the rate of photosynthesis, and differed in their effect on ROS production. The chemicals probably have different mechanisms to exercise their effects: NAC and ASC probably function as antioxidant agents or as precursors of other antioxidant molecules that protect the DNA and photosynthetic apparatus directly from the ROS produced as a result of UV-B radiation, and GPS and MCPA-Na probably disrupt the normal metabolism in S. javanicum to induce the leaking of ROS into the photosynthetic electron transfer pathway following UV-B radiation, and thereby damage the DNA. Such mechanisms have serious implications for the use of environment-friendly herbicides, which, because they can destroy DNA, may prove harmful to soil microorganisms.
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, The Chinese Academy of Sciences, Wuhan 430072, PR China.
authors.forename: Gaohong
authors.initials: G
authors.lastname: Wang
authors.forename: Songqiang
authors.initials: S
authors.lastname: Deng
authors.forename: Cheng
authors.initials: C
authors.lastname: Li
authors.forename: Yongding
authors.initials: Y
authors.lastname: Liu
authors.forename: Lanzhou
authors.initials: L
authors.lastname: Chen
authors.forename: Chaozhen
authors.initials: C
authors.lastname: Hu
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D000458:Cyanobacteria / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects*; D004249:DNA Damage; D004269:DNA, Bacterial / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D003889:Desert Climate; D006540:Herbicides / Q000633:toxicity*; D010788:Photosynthesis / Q000187:drug effects / Q000528:radiation effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D012988:Soil Microbiology; D013482:Superoxide Dismutase / Q000378:metabolism; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D000975:Antioxidants; D004269:DNA, Bacterial; D006540:Herbicides; D017382:Reactive Oxygen Species; D013482:Superoxide Dismutase