小麦应对Cu2+胁迫的生理响应及ASA-GSH合成酶基因表达

抗坏血酸（ascorbate, ASA）- 谷胱甘肽（glutathione, GSH）在植物响应逆境胁迫过程中发挥了重要作用。为探究ASA-GSH在小麦Cu2+胁迫响应中的作用，以小麦品种‘百农207’为材料，用0.05、0.10、0.50、1.00 mmol·L-1 Cu2+进行处理，检测Cu2+对小麦生长参数、受伤害程度、及非酶促反应相关参数ASA和GSH等生理指标的影响，进而测定ASA-GSH循环相关酶基因抗坏血酸过氧化物酶基因（APX）、抗坏血酸还原酶基因（DHAR）、单脱水抗坏血酸还原酶基因（MDHAR）、谷胱甘肽合成酶基因（GR）的表达量。结果表明，随着Cu ²⁺浓度的升高，小麦的株高、根长、总鲜重和总干重逐渐降低，而丙二醛（MDA）、过氧化氢（H₂O₂）、ASA和GSH的含量则显著升高。APX基因在叶片和根中的表达趋势基本一致，在低浓度下（0.05和0.10 mmol·L^-1）表达量显著下降，高浓度下（0.50和1.00 mmol·L^-1）则显著升高；DHAR和GR基因表达趋势相似，在叶片中低浓度表达量显著升高，高浓度则显著下降，在根中则随着浓度的升高而呈现增加的趋势；MDHAR基因在叶片中的表达和DHAR和GR基因相似，在根中则与APX基因相似；上述结果表明,APX、DHAR、MDHAR、GR在转录水平均受到Cu ²⁺胁迫的诱导。综上，ASA-GSH在小麦响应铜胁迫过程中可能发挥了重要作用，并且这一作用的发挥与ASA和GSH含量的改变以及ASA-GSH循环相关酶基因的差异表达密切相关。

Physiological Response and Expression of Genes Encoding Ascorbate-glutathione Synthesis Enzymesto Cu 2+ Stress in Wheat

Ascorbate-glutathione (ASA-GSH) cycle plays an important role in plant response to different stresses. In this study, plants of wheat cultivar ‘Bainong 207’ was used and treated by different Cu ²⁺ concentrations (0.05、0.10、0.50、1.00 mmol·L^-1) to investigate the roles of ASA-GSH under copper stress. Physiological indexes and expression levels of four key enzymes genes in ASA-GSH cycle were determined in wheat plants. Results indicated that the parameters of growth, such as plant height, root length and fresh weight were gradually decreased with the increase of Cu ²⁺ concentration, while contents of malondialdehyde (MDA), hydrogen peroxide (H₂O₂), ASA and GSH were increased under different Cu ²⁺ concentrations treatments. Furthermore, the expression levels of APX (ascorbate peroxidase), DHAR (dehydroascorbate reductase), MDHAR (monodehydroascorbate reductase), and GR (glutathione reductase) in ASA-GSH cycle, had been determined by quantitative real-time PCR (qPCR). Expression trends of APX were the same in leaves and roots, which increased at Cu ²⁺ concentration of 0.05 and 0.10 mmol·L^-1 and decreased at Cu ²⁺ concentration of 0.50 and 1.00 mmol·L^-1, respectively. Expression trends of DHAR and GR were similar, which increased at Cu2+ concentration of 0.05 and 0.10 mmol·L^-1 and decreased at 0.50 and 1.00 mmol·L^-1 in leaves; while their expression levels increased along with the increasing of Cu ²⁺ concentration in roots. Expression levels of MDHAR were similar to DHAR and GR in leaves, and similar to APX in roots. It was demonstrated that these four genes were significantly induced in roots and leaves by Cu ²⁺ stress. To sum up, ASA-GSH might play an important role in response to Cu ²⁺ stress in wheat, which was closely related to the changes of ASA and GSH contents and the differential expression of ASA-GSH cycle related enzyme genes.