Belgian Nuclear Research Center (SCK•CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol, Belgium.
J Environ Radioact. 2011 Jun;102(6):638-45. doi: 10.1016/j.jenvrad.2011.03.013. Epub 2011 Apr 15.
The cellular redox balance seems an important modulator under heavy metal stress. While for other heavy metals these processes are well studied, oxidative stress related responses are also known to be triggered under uranium stress but information remains limited. This study aimed to further unravel the mechanisms by which plants respond to uranium stress. Seventeen-day-old Arabidopsis thaliana seedlings, grown on a modified Hoagland solution under controlled conditions, were exposed to 0, 0.1, 1, 10 and 100 μM uranium for 1, 3 and 7 days. While in Part I of this study oxidative stress related responses in the roots were discussed, this second Part II discusses oxidative stress related responses in the leaves and general conclusions drawn from the results of the roots and the leaves will be presented. As several responses were already visible following 1 day exposure, when uranium concentrations in the leaves were negligible, a root-to-shoot signaling system was suggested in which plastids could be important sensing sites. While lipid peroxidation, based on the amount of thiobarbituric acid reactive compounds, was observed after exposure to 100 μM uranium, affecting membrane structure and function, a transient concentration dependent response pattern was visible for lipoxygenase initiated lipid peroxidation. This transient character of uranium stress responses in leaves was emphasized by results of lipoxygenase (LOX2) and antioxidative enzyme transcript levels, enzyme capacities and glutathione concentrations both in time as with concentration. The ascorbate redox balance seemed an important modulator of uranium stress responses in the leaves as in addition to the previous transient responses, the total ascorbate concentration and ascorbate/dehydroascorbate redox balance increased in a concentration and time dependent manner. This could represent either a slow transient response or a stable increase with regard to plant acclimation to uranium stress.
细胞氧化还原平衡似乎是重金属胁迫下的重要调节剂。虽然对于其他重金属，这些过程已经得到了很好的研究，但铀胁迫下也已知会引发氧化应激相关反应，但信息仍然有限。本研究旨在进一步揭示植物对铀胁迫的响应机制。在受控条件下，用改良的 Hoagland 溶液培养 17 天大的拟南芥幼苗，然后将其暴露于 0、0.1、1、10 和 100μM 铀中 1、3 和 7 天。在本研究的第一部分中讨论了与氧化应激相关的根反应，本第二部分讨论了与氧化应激相关的叶反应，并将从根和叶的结果中得出的一般结论呈现出来。由于在 1 天暴露时已经可以观察到几种反应，而此时叶片中的铀浓度可以忽略不计，因此提出了一种根到茎的信号传递系统，其中质体可能是重要的感应部位。虽然在暴露于 100μM 铀后观察到了基于硫代巴比妥酸反应化合物的量的脂质过氧化，但这会影响膜的结构和功能，而脂氧合酶引发的脂质过氧化表现出短暂的浓度依赖性反应模式。叶片中铀胁迫反应的这种短暂特征通过脂氧合酶 (LOX2) 和抗氧化酶转录水平、酶容量和谷胱甘肽浓度的结果强调，无论是时间还是浓度都呈现出时间和浓度依赖性。叶片中铀胁迫反应的抗坏血酸氧化还原平衡似乎是一个重要的调节剂，因为除了之前的瞬态反应外，总抗坏血酸浓度和抗坏血酸/脱氢抗坏血酸氧化还原平衡以浓度和时间依赖的方式增加。这可能代表植物对铀胁迫的适应是一种缓慢的瞬态反应或稳定的增加。
