State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki 710-0046, Japan.
J Exp Bot. 2017 Nov 28;68(20):5641-5651. doi: 10.1093/jxb/erx364.
Silicon (Si) alleviates cadmium (Cd) toxicity and accumulation in a number of plant species, but the exact molecular mechanisms responsible for this effect are still poorly understood. Here, we investigated the effect of Si on Cd toxicity and accumulation in rice (Oryza sativa) by using two mutants (lsi1 and lsi2) defective in Si uptake and their wild types (WTs). Root elongation was decreased with increasing external Cd concentrations in both WTs and mutants, but Si did not show an alleviative effect on Cd toxicity in all lines. By contrast, the Cd concentration in both the shoots and roots was decreased by Si in the WTs, but not in the mutants. Furthermore, Si supply resulted in a decreased Cd concentration in the root cell sap and xylem sap in the WTs, but not in the mutants. Pre-treatment with Si also decreased Cd accumulation in the WTs, but not in the mutants. Silicon slightly decreased Cd accumulation in the cell wall of the roots. The expression level of OsNramp5 and OsHMA2 was down-regulated by Si in the WTs, but not in the mutants. These results indicate that the Si-decreased Cd accumulation was caused by down-regulating transporter genes involved in Cd uptake and translocation in rice.
硅（Si）可减轻许多植物物种的镉（Cd）毒性和积累，但负责这种效应的确切分子机制仍知之甚少。在这里，我们通过使用两个硅吸收缺陷突变体（lsi1 和 lsi2）及其野生型（WTs）来研究 Si 对水稻（Oryza sativa）Cd 毒性和积累的影响。在 WTs 和突变体中，随着外部 Cd 浓度的增加，根伸长都减少，但 Si 并没有对所有品系的 Cd 毒性表现出缓解作用。相比之下，Si 在 WTs 中降低了地上部和根部的 Cd 浓度，但在突变体中没有。此外，Si 供应导致 WTs 中的根细胞液和木质部汁液中的 Cd 浓度降低，但在突变体中没有。Si 的预处理还降低了 WTs 中的 Cd 积累，但在突变体中没有。Si 轻微降低了根细胞壁中 Cd 的积累。Si 在 WTs 中下调了 OsNramp5 和 OsHMA2 的表达水平，但在突变体中没有。这些结果表明，Si 降低 Cd 积累是通过下调参与水稻 Cd 摄取和转运的转运蛋白基因引起的。
