DataSheet_3_Integrated physiological and metabolomic responses reveal mechanisms of Cd tolerance and detoxification in kenaf (Hibiscus cannabinus L.) under Cd stress.docx

IntroductionCadmium (Cd) is a highly toxic trace element that occurs in large quantities in agricultural soils. The cultivation of industrial crops with high phytoremediation potential, such as kenaf, could effectively reduce soil Cd contamination, but the mechanisms of toxicity, tolerance, and detoxification remain unclear.
MethodsIn this study, the effects of different Cd concentrations (0, 100, 250, and 400 µM) on growth, biomass, Cd uptake, physiological parameters, metabolites and gene expression response of kenaf were investigated in a hydroponic experiment.
Results and discussionThe results showed that Cd stress significantly altered the ability of kenaf to accumulate and transport Cd; increased the activity of hydrogen peroxide (H2O2), superoxide anion (O2−), and malondialdehyde (MDA); reduced the activities of superoxide dismutase (SOD) and catalase (CAT); and decreased the content of photosynthetic pigments, resulting in significant changes in growth and biomass production. Exposure to Cd was found to have a detrimental effect on the ascorbate–glutathione (AsA–GSH) cycle in the roots, whereas it resulted in an elevation in AsA levels and a reduction in GSH levels in the leaves. The increased content of cell wall polysaccharides under Cd stress could contribute to Cd retention in roots and limited Cd transport to above-ground plant tissues. Metabolomic analyses revealed that alanine, aspartate, and glutamate metabolism, oxidative phosphorylation, ABC transporter, and carbon metabolism were the major metabolic pathways associated with Cd stress tolerance. Cd stress increased gene expression of IRT1 and MTP1 in roots, which resulted in kenaf roots accumulating high Cd concentrations. This study extends our knowledge of the factors regulating the response of kenaf to Cd stress. This work provided a physiological and metabolomic perspective on the mechanism controlling the response of kenaf to Cd stress.

引言：镉（Cadmium, Cd）是一种高毒性微量元素，广泛存在于农业土壤中。种植具有高植物修复潜力的工业作物（如洋麻（kenaf)）可有效降低土壤镉污染，但当前关于洋麻应对镉胁迫的毒性、耐受性及解毒机制仍未明确。

方法：本研究通过水培实验，探究了不同镉浓度梯度（0、100、250及400 µM）对洋麻生长状况、生物量积累、镉吸收、生理指标、代谢物谱及基因表达响应的影响。

结果与讨论：结果表明，镉胁迫显著改变了洋麻对镉的积累与转运能力；提升了过氧化氢（hydrogen peroxide, H₂O₂）、超氧阴离子（superoxide anion, O₂⁻）与丙二醛（malondialdehyde, MDA）的积累水平，降低了超氧化物歧化酶（superoxide dismutase, SOD）与过氧化氢酶（catalase, CAT）的活性，同时减少了光合色素含量，最终导致洋麻生长与生物量积累发生显著变化。研究发现，镉胁迫对根部的抗坏血酸-谷胱甘肽（AsA–GSH）循环产生不利影响，而叶片中抗坏血酸（AsA）水平升高、谷胱甘肽（GSH）水平降低。镉胁迫下细胞壁多糖含量升高，有助于根部固持镉并限制其向植株地上部组织转运。代谢组学分析显示，丙氨酸-天冬氨酸-谷氨酸代谢、氧化磷酸化、ABC转运蛋白（ABC transporter）及碳代谢是与镉胁迫耐受性相关的核心代谢通路。镉胁迫上调了根部IRT1与MTP1基因的表达，促使洋麻根部积累高浓度镉。本研究拓展了我们对调控洋麻镉胁迫响应相关因子的认知，从生理与代谢组学视角阐明了洋麻应对镉胁迫的响应机制。