Herbicidal and antioxidant responses of transgenic rice overexpressing Myxococcus xanthus protoporphyrinogen oxidase.
We analyzed the herbicidal and antioxidant defense responses of transgenic rice plants that overexpressed the Myxococcus xanthus protoporphyrinogen oxidase gene. Leaf squares of the wild-type incubated with oxyfluorfen were characterized by necrotic leaf lesions and increases in conductivity and malonyldialdehyde levels, whereas transgenic lines M4 and M7 did not show any change with up to 100 microM oxyfluorfen. The wild-type had decreased F(v)/F(m) and produced a high level of H(2)O(2) at 18 h after foliar application of oxyfluorfen, whereas transgenic lines M4 and M7 were unaffected. In response to oxyfluorfen, violaxanthin, beta-carotene, and chlorophylls (Chls) decreased in wild-type plants, whereas antheraxanthin and zeaxanthin increased. Only a slight decline in Chls was observed in transgenic lines at 48 h after oxyfluorfen treatment. Noticeable increases of cytosolic Cu/Zn-superoxide dismutase, peroxidase isozymes 1 and 2, and catalase were observed after at 48 h of oxyfluorfen treatment in the wild-type. Non-enzymatic antioxidants appeared to respond faster to oxyfluorfen-induced photodynamic stress than did enzymatic antioxidants. Protective responses for the detoxification of active oxygen species were induced to counteract photodynamic stress in oxyfluorfen-treated, wild-type plants. However, oxyfluorfen-treated, transgenic plants suffered less oxidative stress, confirming increased herbicidal resistance resulted from dual expression of M. xanthus Protox in chloroplasts and mitochondria.
Jung
Sunyo
S
Center for Agricultural Biomaterials, Seoul National University, San 56-1, Sillim-dong, Gwanak-gu, Seoul 151-742, South Korea.
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Kyoungwhan
K
D000975:Antioxidants / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D004351:Drug Resistance; D015971:Gene Expression Regulation, Enzymologic; D055768:Halogenated Diphenyl Ethers; D006540:Herbicides / Q000494:pharmacology*; D006861:Hydrogen Peroxide / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D016941:Myxococcus xanthus / Q000201:enzymology* / Q000235:genetics; D012275:Oryza / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics* / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism; D010641:Phenotype; D010647:Phenyl Ethers / Q000494:pharmacology; D030821:Plants, Genetically Modified; D050768:Protoporphyrinogen Oxidase; D013482:Superoxide Dismutase / Q000378:metabolism; D024341:Xanthophylls; D019207:beta Carotene / Q000031:analogs & derivatives / Q000378:metabolism
D000975:Antioxidants; D055768:Halogenated Diphenyl Ethers; D006540:Herbicides; D010647:Phenyl Ethers; D024341:Xanthophylls; D019207:beta Carotene; D002734:Chlorophyll; C016027:oxyfluorofen; C005613:violaxanthin; D006861:Hydrogen Peroxide; D002374:Catalase; D009195:Peroxidase; D013482:Superoxide Dismutase; D044925:Oxidoreductases Acting on CH-CH Group Donors; D050768:Protoporphyrinogen Oxidase