Poster: Oxidative stress

Abs # 64: Relative importance of Na⁺ and Cl^- in NaCl-induced antioxidant systems in roots of rice seedlings

Presenter:	Kao, Ching-Huei , kaoch@ntu.edu.tw
Authors	Kao, Ching-Huei  (A)   Tsai, Yu-Chang  (A)   Hong, Chwan-Yang  (B)   Liu, Li-Fei  (A)
Affiliations:	(A): National Taiwan University (B): Academia Sinica

We investigated the response of antioxidant systems to NaCl stress and the relative importance of Na⁺ and Cl^- in NaCl-induced antioxidant systems in roots of rice seedlings. NaCl treatment caused an increase in the activities of ascorbate peroxidase (APX) and glutathione reductase (GR) in roots of rice seedlings, but had no efect on the activities of superoxie dismutase (SOD) and catalase (CAT). There were detecable differences in APX and GR isoforms between control and NaCl-treated roots. Levels of activity for SOD and CAT isoforms did not change in NaCl-stressed roots. NaCl treatment had higher H₂O₂,ascorbate (AsA), and reduced glutathione (GSH) levels than controls in rice roots. Treatment with 50 mM Na-gluconate (the anion of which is not permeable to membrane) had similar Na⁺ level in roots as that with 100 mM NaCl. It was found that treatment with 50 mM Na-gluconate affected H₂O₂ and AsA levels, APX ang GR activities, OsAPX and OsGR mRNA induction in the same way as 100 mM NaCl. These results suggested that Cl^- is not required for these parametrs caused by NaCl treatment. On the other hand, it was found that NaCl, but not Na-gluconate and NaNO₃, caused an increase in GSH level indicating that Cl^-, rather than Na⁺, is responsible for NaCl-increased GSH level in roots of rice seedlings.