Melatonin has been identified as a potential mitigator of cadmium (Cd) stress in plants, though its precise cellular mechanisms remain poorly understood, particularly regarding its role in detoxification processes within the protoplast and vacuole. This study examines the effects of exogenous melatonin on Cd concentration and vacuolar compartmentalization in the leaf cells of Solanum nigrum L., a recognized hyperaccumulator plant. Employing subcellular separation techniques, we quantified levels of total Cd, Cd2+, ascorbic acid–glutathione (AsA‐GSH), and reactive oxygen species (ROS) in the protoplasts and vacuoles of leaf cells. Results reveal that vacuolar compartmentalization serves as a dynamic mechanism, balancing strategic sequestration and continuous metabolic activity in the cytoplasm, with 72.19%–79.89% of the Cd retained within the vacuole. Melatonin enhanced the effective allocation of these resources, contributing to the preservation of cellular homeostasis. In particular, outside the vacuole, melatonin treatment maintained relatively higher levels of glutathione/oxidized glutathione (GSH/GSSG) and ascorbic acid/dehydroascorbate (AsA/DHA) under 50 μM Cd stress. At this concentration, the AsA/DHA ratio increased from 0.71 to 2.20, and the GSH/GSSG ratio increased from 2.20 to 4.28 outside the vacuole, in comparison to treatment with Cd alone. These findings enhance our understanding of melatonin‐mediated cellular tolerance mechanisms, offer insights for improving plant Cd stress tolerance, and could inform genetic strategies for developing more efficient hyperaccumulator plants.

中文翻译：

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褪黑激素介导的 Solanum nigrum L 中的液泡区室化。在镉应力下


褪黑激素已被确定为植物中镉 （Cd） 应激的潜在缓解剂，尽管其确切的细胞机制仍然知之甚少，特别是关于它在原生质体和液泡内的解毒过程中的作用。本研究研究了外源褪黑激素对 Solanum nigrum L. 叶细胞中 Cd 浓度和液泡区室化的影响，Solanum nigrum L. 是一种公认的高积累植物。采用亚细胞分离技术，我们量化了叶细胞原生质体和液泡中总 Cd、Cd2+、抗坏血酸-谷胱甘肽 （AsA-GSH） 和活性氧 （ROS） 的水平。结果显示，液泡区室化是一种动态机制，平衡细胞质中的策略性隔离和连续代谢活动，72.19%–79.89% 的 Cd 保留在液泡内。褪黑激素增强了这些资源的有效分配，有助于维持细胞稳态。特别是，在液泡之外，褪黑激素处理在 50 μM Cd 胁迫下保持相对较高的谷胱甘肽/氧化谷胱甘肽 （GSH/GSSG） 和抗坏血酸/脱氢抗坏血酸 （AsA/DHA） 水平。与单独使用 Cd 处理相比，在该浓度下，AsA/DHA 比率从 0.71 增加到 2.20，液泡外的 GSH/GSSG 比率从 2.20 增加到 4.28。这些发现增强了我们对褪黑激素介导的细胞耐受性机制的理解，为提高植物 Cd 胁迫耐受性提供了见解，并可能为开发更高效的超积累植物的遗传策略提供信息。