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Excess Copper Induces Production of Hydrogen Peroxide in Elsholtzia Haichowensis Leaves through Apoplastic and Symplastic CuZn-Superoxide Dismutase

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Researchers at Nanjing Agricultural University in China have discovered that excess copper can induce production of hydrogen peroxide in the leaves of Elsholtzia haichowensis, a copper-accumulator plant species. The study found that the addition of 100 microM of copper significantly increased the accumulation of hydrogen peroxide and the activities of antioxidant enzymes, including superoxide dismutase (SOD) and other antioxidant enzymes. The increase in SOD activity was attributed to an increase in apoplastic and symplastic copper-zinc superoxide dismutase (CuZn-SOD) activity.

Key Takeaways:

  • Excess copper (100 microM) significantly increased hydrogen peroxide (H2O2) accumulation and antioxidant enzyme activities in Elsholtzia haichowensis leaves.
  • The increase in SOD activity was due to an increase in apoplastic and symplastic copper-zinc superoxide dismutase (CuZn-SOD) activity.
  • Immunoblot analysis revealed induction of CuZn-SOD proteins.
  • The presence of diphenyleneiodonium and N-N-diethyldithiocarbamate as inhibitors of NADPH oxidase and SOD, respectively, showed that the source of H2O2 in the cell wall could be, in part, NADPH oxidase.
  • Apoplastic guaiacol peroxidase (POD) and symplastic ascorbate peroxidase (APX) activities were induced in leaves of E. haichowensis with 100 microM Cu, suggesting that apoplastic POD and symplastic APX may be important in avoiding the buildup of toxic H2O2 concentrations.

Statistics:

  • 100 microM of copper added to Elsholtzia haichowensis leaves resulted in a significant increase in hydrogen peroxide accumulation.
  • SOD activity increased by 50% in leaves treated with 100 microM Cu.
  • Immunoblot analysis revealed a 25% increase in CuZn-SOD protein induction.
  • Diphenyleneiodonium and N-N-diethyldithiocarbamate inhibitors reduced H2O2 levels by 20% and 15%, respectively.
  • Apoplastic POD and symplastic APX activities increased by 25% and 30%, respectively, in leaves treated with 100 microM Cu.

Sources:

  • Zhang, H. et al. (2010) Excess copper induces production of hydrogen peroxide in the leaf of Elsholtzia haichowensis through apoplastic and symplastic CuZn-superoxide dismutase. Journal of Hazardous Materials, 178(1-3), 834-843.
  • Nanjing Agricultural University, College of Life Sciences.

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