Lai Qi-xian, Bao Zhi-yi, Zhu Zhu-jun, Qian Qiong-qiu, Mao Bi-zeng
Key Laboratory of Horticultural Plant Development and Biotechnology, Department of Horticulture, Zhejiang University, Hangzhou 310029, China.
J Zhejiang Univ Sci B. 2007 Jul;8(7):458-64. doi: 10.1631/jzus.2007.B0458.
Leaf senescence is often caused by water deficit and the chimeric gene P(SAG12)-IPT is an auto-regulated gene delaying leaf senescence. Using in vitro leaf discs culture system, the changes of contents of chlorophylls, carotenoids, soluble protein and thiobarbituric acid reactive substance (TBARS) and antioxidant enzymes activities were investigated during leaf senescence of P(SAGl2)-IPT modified gerbera induced by osmotic stress compared with the control plant (wild type). Leaf discs were incubated in 20%, 40% (w/v) polyethylene glycol (PEG) 6000 nutrient solution for 20 h under continuous light [130 micromol/(m(2) x s)]. The results showed that the contents of chlorophylls, carotenoids and soluble protein were decreased by osmotic stress with the decrease being more pronounced at 40% PEG, but that, at the same PEG concentration the decrease in the transgenic plants was significantly lower than that in the control plant. The activities of superoxide dismutase (SOD), catalases (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and dehydroascorbate reductase (DHAR) were stimulated by PEG treatment. However, the increases were higher in P(SAG12)-IPT transgenic plants than in the control plants, particularly at 40% PEG treatment. Lipid peroxidation (TBARS content) was increased by PEG treatment with the increase being much lower in transgenic plant than in the control plant. It could be concluded that the increases in the activities of antioxidant enzymes including SOD, CAT, APX, GPX and DHAR were responsible for the delay of leaf senescence induced by osmotic stress.
叶片衰老通常由水分亏缺引起，嵌合基因P(SAG12)-IPT是一种能延缓叶片衰老的自调控基因。利用离体叶片圆盘培养系统，研究了渗透胁迫诱导的P(SAGl2)-IPT转基因非洲菊与对照植株（野生型）叶片衰老过程中叶绿素、类胡萝卜素、可溶性蛋白和硫代巴比妥酸反应物质（TBARS）含量的变化以及抗氧化酶活性的变化。将叶片圆盘置于20%、40%（w/v）聚乙二醇（PEG）6000营养液中，在连续光照[130微摩尔/(平方米·秒)]下培养20小时。结果表明，渗透胁迫导致叶绿素、类胡萝卜素和可溶性蛋白含量下降，在40%PEG处理下下降更为明显，但在相同PEG浓度下，转基因植株的下降幅度明显低于对照植株。超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、抗坏血酸过氧化物酶（APX）、愈创木酚过氧化物酶（GPX）和脱氢抗坏血酸还原酶（DHAR）的活性受到PEG处理的刺激。然而，P(SAG12)-IPT转基因植株的活性增加幅度高于对照植株，尤其是在40%PEG处理下。PEG处理使脂质过氧化（TBARS含量）增加，转基因植株的增加幅度远低于对照植株。可以得出结论，包括SOD、CAT、APX、GPX和DHAR在内的抗氧化酶活性的增加是渗透胁迫诱导叶片衰老延迟的原因。
