Department of Agronomy, National Taiwan University, Taipei, Taiwan, ROC.
Plant Physiol Biochem. 2010 May;48(5):374-81. doi: 10.1016/j.plaphy.2010.01.009. Epub 2010 Jan 21.
Cadmium (Cd) toxicity of rice (Oryza sativa L. cv. Taichung Native 1) seedlings was evaluated by the decrease in chlorophyll content and the increase in malondialdehyde (MDA) in the second leaves of rice seedlings. CdCl2 (5 microM) treatment was accompanied by a decrease in the contents of ascorbic acid (AsA) and AsA + dehydroascorbate (DHA) and in the ratios of AsA/DHA in leaves. However, CdCl2 treatment resulted in an increase in DHA content in leaves. Moreover, the decrease in AsA content was prior to the occurrence of chlorosis and associated with the increase in MDA content in the leaves of seedlings treated with Cd. Pretreatment with 0.5 mM AsA or L-galactono-1,4-lactone (GalL), the biosynthetic precursor of AsA, for 6 h resulted in an increase in the contents of AsA and reduced glutathione (GSH), the ratios of AsA/DHA and GSH/oxidized glutathione, and the activities of ascorbate peroxidase (APX) and glutathione reductase (GR) in the leaves of rice seedlings. Quantitative RT-PCR was applied to quantify the mRNA levels for OsAPX and OsGR genes from rice leaves to examine the effect of AsA or GalL pretreatment on the expression of OsAPX and OsGR genes in rice leaves. The expression of OsAPX2, OsAPX3, OsAPX4, OsAPX5, OsAPX6, OsAPX7, and OsGR1 was increased by AsA or GalL pretreatment. Rice seedlings pretreated with AsA or GalL were observed to reduce the subsequent Cd-induced toxicity. Our results suggest that AsA content may play a role in regulating Cd toxicity of rice seedlings.
采用水稻（Oryza sativa L. cv. Taichung Native 1）幼苗第二叶片叶绿素含量降低和丙二醛（MDA）含量增加的方法评价镉（Cd）对水稻幼苗的毒性。CdCl2（5 μM）处理伴随着叶片中抗坏血酸（AsA）和 AsA+脱氢抗坏血酸（DHA）含量以及 AsA/DHA 比值的降低。然而，CdCl2 处理导致叶片中 DHA 含量增加。此外，AsA 含量的降低先于叶片出现黄化，并与用 Cd 处理的幼苗叶片中 MDA 含量的增加相关。用 0.5 mM AsA 或 L-半乳糖酸-1,4-内酯（GalL）（AsA 的生物合成前体）预处理 6 h 导致叶片中 AsA 和还原型谷胱甘肽（GSH）含量增加、AsA/DHA 和 GSH/氧化型谷胱甘肽比值增加、以及抗坏血酸过氧化物酶（APX）和谷胱甘肽还原酶（GR）活性增加。采用定量 RT-PCR 方法从水稻叶片中定量 OsAPX 和 OsGR 基因的 mRNA 水平，以研究 AsA 或 GalL 预处理对水稻叶片中 OsAPX 和 OsGR 基因表达的影响。AsA 或 GalL 预处理增加了 OsAPX2、OsAPX3、OsAPX4、OsAPX5、OsAPX6、OsAPX7 和 OsGR1 的表达。用 AsA 或 GalL 预处理的水稻幼苗观察到减轻了随后的 Cd 诱导的毒性。我们的结果表明，AsA 含量可能在调节水稻幼苗的 Cd 毒性中发挥作用。
