水稻根系系统在硒调控锑吸收方面的作用机理研究

Antimony (Sb) is a toxic carcinogenic element. In China soil, water, and agricultural products have been seriously polluted by Sb in some areas due to some natural and artificial factors. High levels of Sb in environment can decrease the yields of paddy-rice and threaten the health of humans. Previous studies have shown that Sb is not an essential element to plants, but it can be accumulated by plants. Excess Sb can produce damages to plants. Our previous studies have shown that low doses of selenium (Se) can be used to reduce the uptake of antimony through affecting the root growth of paddy rice, and changing the root morphology. However, there are some questions will be left to be resolved, for example, why and how the interaction between Se and Sb can affect the root development of paddy rice? at the same time, the roles of root system of paddy rice in regulating Sb uptake are what? and are there potential mechanisms? In this study, we will investigate the mechanisms on: 1) the effects of interaction between different forms of Se and Sb on the concentrations of root excretions of paddy rice and its relationship with the regultaion of Sb uptake by Se; 2) how root development, formation of oxyradicals and elemental uptake and distribution in cell level in paddy rice can influence the regulation of Sb uptake by Se; 3) the roles of hormones, saccharides and some enzymes related with the formation and extension of root cell wall in regulting Sb uptake under the influence of Se. Some advanced technologies will be applied, such as differential centrifugation separation technology, SEM/TEM technology in combination with energy spectrum analysis,high performance liquid chromatography, high performance liquid chromatography combined with inductively coupled plasma mass spectrometry, chromatography of ions and fluorescence confocal microscopy. It is hoped that the results of this study will help people understand the mechanisms on the detoxification of Sb by Se, and in practice make supply people with feasible technological means to guarantee the safety of crop and food in future.

锑(Sb)是一种致癌元素，我国部分地区水稻受到严重的Sb污染。我们前期研究结果表明，硒(Se)能通过影响水稻根系发育、改变根系形态调控水稻对Sb的吸收，但是关于Se/Sb交互作用为何能影响水稻根系发育的机理研究还十分缺乏，同时关于根系系统在Se调控Sb吸收方面的作用机理还不明确。本项目以水稻为研究对象，利用扫描/透射电镜-能谱分析、荧光共聚焦显微等技术，重点研究：Se/Sb交互作用对水稻根系分泌物的影响及其与Se调控Sb吸收之间的关系；根系发育、根系氧化自由基形成、元素吸收及细胞水平分布与Se缓解Sb毒性之间的关系；与根系细胞壁形成及扩展相关的激素、糖类、酶类在Se/Sb处理下的水稻根系发育及Se调控Sb吸收方面所起的作用，揭示根系系统在Se调控Sb吸收方面的作用机理。其研究成果在理论上可揭示Se缓解Sb毒害效应的机理，在实践中可为保障我国粮食和食品安全提供切实可行的技术手段。

硒(Se)是一种人体必需的营养元素，而我国部分地区居民面临着日均Se摄入量不足的问题。低剂量的Se对植物有益，可缓解植物多种逆境胁迫，包括重(类)金属胁迫。前人的研究指出：Se缓解重(类)金属胁迫的机制主要围绕着抗氧化体系调控、光合作用调控、植物膜系统的调控、必需营养元素的调控以及直接对重(类)金属的吸收抑制。但关于Se抑制重(类)金属“广谱性”的机制还不清楚。本研究以植物根系系统为研究对象，采用了如下技术系统研究了Se降低植物重(类)金属吸收/转运间的机理，包括：非损伤微测、荧光共聚焦显微、根系扫描、超高效液相色谱、傅里叶红外光谱、光电子能谱、转录组、代谢组等技术，1)分析了Se降低植物对重(类)金属吸收的效率；2)分析了Se/重(类)金属处理下多种根系分泌的有机酸含量；3)阐明了根系铁膜形成与Se调控重(类)金属吸收间的关系；4)明确了根系形态变化与激素的合成、相关基因调控/信号转导、元素吸收间的关系；5)分析了细胞壁组份含量响应，相关酶、基因和代谢物的调控机制，阐述了上述组份的合成/相互作用与根系生长、根系形态变化、元素吸收/固定间的逻辑关系。重要结果包括：Se增加了果胶的总糖和半乳糖醛酸的含量、促进了果胶去甲酯化水平；增加了半纤维素2的总糖和半乳糖醛酸的含量；影响了果胶、半纤维素、纤维素、木质素间的网络互作，从而影响了细胞壁结构稳定性以及根系细胞生长；促进了胼胝质和凯氏带的沉积，从而抑制目标元素转运。6)研究了细胞壁功能基团的变化。本研究系统且深入地研究了Se降低重(类)金属吸收转运的机制，可为Se降低重(类)金属吸收相关技术的研发提供理论支持。