[论文解读] Efficacy of Put and Spd sprayed on leaves from Brassica juncea plants against Cd2+-induced oxidative stress

Michel Aoun, Annick Hourmant+1 more|ArXiv.org|Dec 12, 2008

Polyamine Metabolism and Applications参考文献 26被引用 3

一句话总结

本研究探讨了外源施加的腐胺（Put）和亚精胺（Spd）在镉离子（Cd²⁺）诱导的氧化应激下对 *Brassica juncea* 植株的保护作用。叶面喷施Put和Spd显著降低了氧化损伤标志物（MDA和GPOX活性），维持了叶绿素含量，并缓解了生长抑制，其中Spd在减少叶片Cd积累和更有效地提升色素水平方面优于Put。

ABSTRACT

The protective effect exerted by polyamines (Put and Spd) against cadmium (Cd) stress was investigated in Brassica juncea plants. Treatment with CdCl2 (75 micro-Mole) resulted in a rise of Cd accumulation, a decrease of fresh and dry weights in every plant organ, an increase of free polyamine content at limb and stem levels as well as a decrease at root level. On the other hand, the total conjugated polyamine levels in the stem tissues were unaffected by Cd. In the leaf tissues, this metal caused a reduction of chlorophyll a content, a rise of guaiacol peroxidase (GPOX) activity and an increase of malondialdehyde (MDA), soluble glucide, proline and amino acid contents. Exogenous application, by spraying, of putrescine (Put) and spermidine (Spd) to leaf tissues reduced CdCl2-induced stress. These polyamines proved to exert a partial, though significant, protection of the foliar fresh weight and to alleviate the oxidative stress generated by Cd through reductions of MDA amounts and GPOX (E.C.1.11.1.7) activity. The enhancement of chlorophyll a content in plants by Put and those of Chl a and Chl b by Spd both constitute evidences of their efficacy against the Cd2+-induced loss of pigments. Conversely to Put, Spd caused a decrease of Cd content in leave tissues and a rise in the stems and roots; these findings are in favour of a stimulation of Cd uptake by Spd. The proline stimulation observed with Cd was reduced further to the spraying of Put onto tissues, but the decrease induced by Spd was more limited. In the plants treated with Cd, the amino acid contents in the leaves were unaffected by Put and Spd spraying; on the other hand, Cd2+ disturbed polyamine levels (free and acido-soluble conjugated-forms); we notice the rise of total free PAs and the decrease of their conjugated-ones.

研究动机与目标

• 评估外源多胺（Put和Spd）在 *Brassica juncea* 中对Cd²⁺诱导的氧化应激的保护作用。
• 评估Put和Spd对植物组织中Cd积累和分布的影响。
• 确定多胺处理对氧化应激标志物（如MDA和GPOX活性）的影响。
• 研究Put和Spd对叶绿素含量和生长参数（鲜重和干重）的影响。
• 分析Cd胁迫下及多胺处理后游离和结合态多胺水平的变化。

提出的方法

• 以75 µM的CdCl₂处理 *Brassica juncea* 植株以诱导氧化应激。
• 通过直接喷施Put和Spd于叶片组织，评估外源施用的效果。
• 使用标准分析技术测定根、茎和叶中的Cd积累量。
• 定量测定氧化应激标志物：丙二醛（MDA）、愈创木酚过氧化物酶（GPOX）活性及脯氨酸水平。
• 通过分光光度法测定叶绿素a和b的含量。
• 使用HPLC或类似方法测定叶、茎和根组织中游离和结合态多胺的水平。

实验结果

研究问题

• RQ1 外源Put和Spd如何影响 *Brassica juncea* 不同器官中的Cd积累？
• RQ2 Put和Spd在多大程度上降低了Cd胁迫植株中的氧化应激标志物（MDA和GPOX）？
• RQ3 Put和Spd是否能缓解Cd诱导的 *Brassica juncea* 叶片中叶绿素降解？
• RQ4 多胺施用如何影响Cd胁迫下内源游离和结合态多胺池的变化？
• RQ5 Put与Spd在生长参数（鲜重和干重）及脯氨酸含量方面有何差异性影响？

主要发现

• 外源施加Put和Spd显著降低了丙二醛（MDA）水平，表明脂质过氧化程度降低，氧化应激减轻。
• 作为氧化应激标志物的GPOX活性在Cd胁迫植株中均被Put和Spd处理显著降低。
• Put和Spd均缓解了Cd诱导的叶绿素a降解，其中Spd对叶绿素a和叶绿素b均表现出更显著的保护作用。
• 喷施Put和Spd维持了叶片的鲜重，表明对Cd诱导的生长抑制具有部分但显著的缓解作用。
• Spd处理降低了叶片组织中的Cd含量，但增加了茎和根中的Cd含量，表明可能促进了Cd的转运或吸收。
• Cd诱导的脯氨酸上升在Put处理下进一步加剧，而Spd处理则影响较小，表明对渗透保护物质合成的调节作用存在差异。