College of Resources and Environment, Huazhong Agricultural University, Wuhan, Hubei, 430070, China.
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, Hubei, 430070, China.
New Phytol. 2013 Nov;200(3):691-699. doi: 10.1111/nph.12494. Epub 2013 Sep 18.
The stresses acting on plants that are alleviated by silicon (Si) range from biotic to abiotic stresses, such as heavy metal toxicity. However, the mechanism of stress alleviation by Si at the single-cell level is poorly understood. We cultivated suspended rice (Oryza sativa) cells and protoplasts and investigated them using a combination of plant nutritional and physical techniques including inductively coupled plasma mass spectrometry (ICP-MS), the scanning ion-selective electrode technique (SIET) and X-ray photoelectron spectroscopy (XPS). We found that most Si accumulated in the cell walls in a wall-bound organosilicon compound. Total cadmium (Cd) concentrations in protoplasts from Si-accumulating (+Si) cells were significantly reduced at moderate concentrations of Cd in the culture medium compared with those from Si-limiting (-Si) cells. In situ measurement of cellular fluxes of the cadmium ion (Cd(2+) ) in suspension cells and root cells of rice exposed to Cd(2+) and/or Si treatments showed that +Si cells significantly inhibited the net Cd(2+) influx, compared with that in -Si cells. Furthermore, a net negative charge (charge density) within the +Si cell walls could be neutralized by an increase in the Cd(2+) concentration in the measuring solution. A mechanism of co-deposition of Si and Cd in the cell walls via a [Si-wall matrix]Cd co-complexation may explain the inhibition of Cd ion uptake, and may offer a plausible explanation for the in vivo detoxification of Cd in rice.
硅（Si）缓解的植物胁迫范围从生物胁迫到非生物胁迫，例如重金属毒性。然而，硅在单细胞水平缓解胁迫的机制还知之甚少。我们培养了悬浮水稻（Oryza sativa）细胞和原生质体，并结合植物营养和物理技术对其进行了研究，这些技术包括电感耦合等离子体质谱（ICP-MS）、扫描离子选择性电极技术（SIET）和 X 射线光电子能谱（XPS）。我们发现，大多数硅以细胞壁结合的有机硅化合物的形式积累在细胞壁中。与 Si 限制（-Si）细胞相比，在培养基中存在中等浓度 Cd 的情况下，来自 Si 积累（+Si）细胞的原生质体中的总镉（Cd）浓度显著降低。在悬浮细胞和暴露于 Cd（2+）和/或 Si 处理的水稻根细胞中对 Cd 离子（Cd（2+））的细胞通量进行原位测量表明，与 -Si 细胞相比，+Si 细胞显著抑制了 Cd（2+）的净流入。此外，+Si 细胞壁内的净负电荷（电荷密度）可以通过测量溶液中 Cd（2+）浓度的增加来中和。Si 和 Cd 在细胞壁中共沉积的机制可能是通过 [Si-壁基质]Cd 共配合物实现的，这可能解释了 Cd 离子摄取的抑制作用，并为水稻体内 Cd 的解毒作用提供了合理的解释。
