Nitrate Reductase-Dependent Nitric Oxide Production Is Involved in Microcystin-LR-Induced Oxidative Stress in Brassica rapa

Chen, Jian; Zhong, You Ming; Zhang, Hai Qiang; Shi, Zhi Qi

Nitrate Reductase-Dependent Nitric Oxide Production Is Involved in Microcystin-LR-Induced Oxidative Stress in Brassica rapa

2012

Chen, Jian | Zhong, You Ming | Zhang, Hai Qiang | Shi, Zhi Qi

Histochemical and biochemical approaches were used to investigate the phytotoxicity induced by microcystin-LR (MC-LR) in the shoots of Brassica rapa seedlings. MC-LR exposure was able to induce oxidative stress by triggering the over-generation of reactive oxygen species (ROS) including superoxide anion radical (O₂ [SÊ¸áµáµáµË¡: Ë¢áµáµ áµáµË£áµ] ⁻ ) and hydrogen peroxide (H₂O₂) in the shoots of B. rapa. MC-LR exposure led to the significant increase in the concentration of endogenous nitric oxide (NO) in B. rapa. However, such increase was completely suppressed by the treatment with nitrate reductase (NR) inhibitor NaN₃, while L-NMMA, a NO synthase (NOS) inhibitor, had only slight effect on the content of endogenous NO in MC-LR-treated plant. These data suggested that NR-dependent pathway was the main source for endogenous NO generation under MC-LR stress. Afterwards, treatment with NaN₃ reduced the ROS generation, lipid peroxidation, and loss of membrane integrity in MC-LR-treated plant. MC-LR stress induced the increase in the expression of superoxide dismutase, ascorbate peroxidase, and catalase. However, such an effect could be reversed by the treatment with NaN₃. These results indicate that NR-dependent NO production mediates MC-LR-induced oxidative stress by triggering the over-generation of ROS in B. rapa.

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