Department of Ecology, Environment and Plant Science, Stockholm University, 106 91 Stockholm, Sweden.
Department of Botany, University of Rajshahi, Rajshahi 6205, Bangladesh.
Environ Pollut. 2016 Apr;211:90-7. doi: 10.1016/j.envpol.2015.12.027. Epub 2015 Dec 30.
Cadmium (Cd) is a health threat all over the world and high Cd content in wheat causes high Cd intake. Silicon (Si) decreases cadmium content in wheat grains and shoot. This work investigates whether and how silicate (Si) influences cadmium (Cd) uptake at the cellular level in wheat. Wheat seedlings were grown in the presence or absence of Si with or without Cd. Cadmium, Si, and iron (Fe) accumulation in roots and shoots was analysed. Leaf protoplasts from plants grown without Cd were investigated for Cd uptake in the presence or absence of Si using the fluorescent dye, Leadmium Green AM. Roots and shoots of plants subjected to all four treatments were investigated regarding the expression of genes involved in the Cd uptake across the plasma membrane (i.e. LCT1) and efflux of Cd into apoplasm or vacuole from the cytosol (i.e. HMA2). In addition, phytochelatin (PC) content and PC gene (PCS1) expression were analysed. Expression of iron and metal transporter genes (IRT1 and NRAMP1) were also analysed. Results indicated that Si reduced Cd accumulation in plants, especially in shoot. Si reduced Cd transport into the cytoplasm when Si was added both directly during the uptake measurements and to the growth medium. Silicate downregulated LCT1 and HMA2 and upregulated PCS1. In addition, Si enhanced PC formation when Cd was present. The IRT1 gene, which was downregulated by Cd was upregulated by Si in root and shoot facilitating Fe transport in wheat. NRAMP1 was similarly expressed, though the effect was limited to roots. This work is the first to show how Si influences Cd uptake on the cellular level.
镉 (Cd) 是全球范围内的健康威胁，而小麦中的高 Cd 含量会导致高 Cd 摄入量。硅 (Si) 可以降低小麦籽粒和茎叶中的 Cd 含量。本研究旨在探讨硅 (Si) 是否以及如何影响小麦细胞水平对 Cd 的吸收。在有无 Cd 的情况下，小麦幼苗在有无 Si 的条件下生长。分析了根系和地上部的 Cd、Si 和铁 (Fe) 积累。在有无 Si 的情况下，使用荧光染料 Leadmium Green AM 研究了在不含 Cd 的植物叶片原生质体对 Cd 的吸收情况。用四种处理方法处理过的根和地上部的植物，研究了参与跨质膜 Cd 吸收的基因（即 LCT1）和将 Cd 从细胞质排入质外体或液泡的基因（即 HMA2）的表达情况。此外，还分析了植物螯合肽 (PC) 含量和 PC 基因 (PCS1) 的表达。还分析了铁和金属转运基因 (IRT1 和 NRAMP1) 的表达。结果表明，Si 减少了植物中 Cd 的积累，尤其是在地上部。当 Si 在吸收测量期间和在生长培养基中直接添加时，Si 减少了 Cd 向细胞质的转运。硅酸盐下调了 LCT1 和 HMA2，上调了 PCS1。此外，当 Cd 存在时，Si 增强了 PC 的形成。Cd 下调的铁转运基因 IRT1 在根和地上部被 Si 上调，促进了小麦中铁的转运。NRAMP1 的表达情况相似，尽管这种影响仅限于根部。本研究首次表明 Si 如何影响细胞水平的 Cd 吸收。
