Salix matsudana Koidz is a low cadmium (Cd)-accumulating willow, whereas its cultivated variety, Salix matsudana var. matsudana f. umbraculifera Rehd., is a high Cd-accumulating and tolerant willow (HCW). The physiological and molecular mechanisms underlying differential Cd accumulation and tolerance in the two Salix species are poorly understood. Here, we confirmed that the differential Cd translocation capacity from roots to the shoots leads to the differential Cd accumulation in their aboveground parts between these two willow genotypes. Cadmium accumulation happens preferentially in the transport pathway, and Cd is mainly located in the vacuolar, cell wall and intercellular space in HCW bark by cadmium location analysis at tissue and subcellular levels. Comparative transcriptome analysis revealed that higher expressions of several metal transporter genes (ATP-binding cassette transporters, K⁺ transporters/channels, yellow stripe-like proteins, zinc-regulated transporter/iron-regulated transporter-like proteins, etc.) are involved in root uptake and translocation capacity in HCW; meanwhile, ascorbate–glutathione metabolic pathways play essential roles in Cd detoxification and higher tolerance of the Cd-accumulator HCW. These results lay the foundation for further understanding the molecular mechanisms of Cd accumulation in woody plants and provide new insights into molecular-assisted-screening woody plant varieties for phytoremediation.

中文翻译：

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转运蛋白和抗坏血酸-谷胱甘肽代谢对两种不同的柳树基因型镉吸收的差异和耐受性。

柳柳Koidz是一种低镉（Cd）积累的柳树，而其栽培品种柳柳Salix matsudana var。松达纳河 umbraculifera Rehd。是一种高Cd积累和耐受性的柳树（HCW）。两种柳中镉差异累积和耐性的生理和分子机制物种了解甚少。在这里，我们证实了从根到芽的Cd差异转运能力导致了这两种柳树基因型之间在地上部分的Cd累积差异。镉的积累优先发生在运输途径中，通过组织和亚细胞水平的镉定位分析，镉主要位于重金属丝树皮的液泡，细胞壁和细胞间空间。比较转录组分析显示，一些金属转运蛋白基因（ATP结合盒转运蛋白，K ⁺转运蛋白/通道，黄色条纹样蛋白，锌调节转运蛋白/铁调节转运蛋白样蛋白等）参与了高碳废物的根吸收和转运能力。同时，抗坏血酸-谷胱甘肽的代谢途径在Cd排毒和Cd蓄积器HCW的更高耐受性中起着重要作用。这些结果为进一步了解木本植物中Cd积累的分子机制奠定了基础，并为分子辅助筛选木本植物品种进行植物修复提供了新见识。