College of Life Sciences, Tianjin Normal University, Tianjin 300387, China.
BMC Plant Biol. 2010 Oct 21;10:225. doi: 10.1186/1471-2229-10-225.
Increased Al concentration causes reduction of mitotic activity, induction of nucleolar alteration, increase of the production of ROS and alteration of several antioxidant enzyme activities in plant cells. Allium cepa is an excellent plant and a useful biomarker for environmental monitoring. Limited information is available about the effects of Al on nucleoli, antioxidant enzyme system, contents of MDA and soluble protein in A. cepa. Therefore, we carried out the investigation in order to better understand the effects of Al on the growth, nucleoli in root tip cells and selected physiological and biochemical characters.
The results showed that the root growth exposed to 50 μM Al was inhibited significantly. 50 μM Al could induce some particles of argyrophilic proteins scattered in the nuclei and extruded from the nucleoli into the cytoplasm. The nucleolus did not disaggregate normally and still remained its characteristic structure during metaphase. Nucleolar reconstruction was inhibited. 50 μM Al induced high activities of SOD and POD in leaves and roots significantly (P < 0.05) when compared with control, whereas the level of CAT was low significantly (P < 0.05). At 50 μM Al the content of MDA in leaves was high significantly (P < 0.05) at 9(th) day and in roots increased (P < 0.05) with prolonging the treatment time during 6-12 days. The soluble protein content in leaves treated with 50 μM Al was high significantly (P < 0.05) at 6(th) day and increased with prolonging the treatment time.
We suggest that variations in nucleoli and the alterations of antioxidant enzyme activities, MDA and soluble protein contents in Allium cepa can serve as useful biomarkers, which can provide valuable information for monitoring and forecasting effects of exposure to Al in real scenarios conditions. Among the antioxidant enzymes SOD and POD appear to play a key role in the antioxidant defense mechanism under Al toxicity condition. Data from MDA concentration show that Al indirectly produces superoxide radicals, resulting in increased lipid peroxidative products and oxidative stress.
铝浓度的增加会导致有丝分裂活性降低、核仁改变、活性氧（ROS）产生增加以及几种植物细胞抗氧化酶活性改变。洋葱是一种极好的植物，也是环境监测的有用生物标志物。关于铝对核仁、抗氧化酶系统、MDA 和可溶性蛋白含量的影响，目前的信息有限。因此，我们进行了这项研究，以便更好地了解铝对洋葱生长、根尖细胞核仁以及选定的生理生化特性的影响。
结果表明，暴露于 50μM 铝的根生长受到显著抑制。50μM 铝可诱导一些嗜银蛋白颗粒散在核内，并从核仁挤出到细胞质中。核仁不能正常解聚，在中期仍保持其特征结构。核仁重建受到抑制。与对照相比，50μM 铝显著诱导叶片和根中 SOD 和 POD 活性升高（P<0.05），而 CAT 水平显著降低（P<0.05）。在 50μM Al 下，叶片中 MDA 的含量在第 9 天显著升高（P<0.05），在第 6-12 天处理时间延长时根中 MDA 的含量也升高（P<0.05）。用 50μM Al 处理的叶片中可溶性蛋白含量在第 6 天显著升高（P<0.05），并随着处理时间的延长而增加。
我们认为，洋葱核仁的变化以及抗氧化酶活性、MDA 和可溶性蛋白含量的改变可以作为有用的生物标志物，为在实际场景条件下监测和预测铝暴露的影响提供有价值的信息。在抗氧化酶中，SOD 和 POD 似乎在铝毒性条件下的抗氧化防御机制中发挥关键作用。从 MDA 浓度数据可以看出，铝间接产生超氧自由基，导致脂质过氧化产物增加和氧化应激。
