Na+/H+ 逆向转运蛋白提高浮萍镉胁迫抗性的机制研究

The industrial discharge leads to the pollution of water system, with cadmium being the most serious one, and causes a severe impact on the aquatic plants. It has been reported that the expression of Na+/H+ Antiporter 1 (NHX1), a salt tolerant gene, decreases first with the cadium stress and then increases. Duckweed（Lemnaceae）, a type of aquatic plants, is wildly explored in water environmental detection, biofuel research and water purification. Glycine max Na+/H+ Antiporter (GmNHX1) was overexpressed in Lemna minor in our study, and the transgenic duckweed show ed cadmium resistance. We need to further study the function of NHX1 on cadmium transportation, the influence of pH value change, organic acids, and the plant signal regulation on the resistance of cadmium stress. The transgenic Duckweed will be researched as a main material for the following aspects: the location of absorb of cadmium in duckweed with cadmium stress and the concentration; the change of pH value change and the organic acids compounds and the influence of these changes of on the absorb of cadmium; the change of ethylene and NO releasing and the expression of related genes. This study tends to reveal the mechanism of NHX1 improving cadmium resistance, and contribute to the understanding of cadmium resistance study and the ecological restoration of cadmium pollution water system.

工业污染物的不当排放导致了水体污染，其中镉污染尤为突出，对水生植物造成了严重危害。研究报道抗盐基因Na+/H+ 逆向转运蛋白（NHX1）的表达在镉胁迫下先降低后升高，出现了显著变化。浮萍在水环境检测、生物产能和水体净化中被广泛应用，我们将大豆的NHX1基因在浮萍中过表达后，初步发现NHX1转基因浮萍具有镉胁迫抗性，然而NHX1抗镉胁迫的机制尚不明确。NHX1在镉离子转运中的作用，以及在pH、有机酸、信号通路等方面对镉胁迫抗性的影响需要解析。本研究拟以NHX1转基因浮萍为材料，研究镉胁迫下NHX1转基因浮萍镉吸收的部位和浓度；pH、有机酸的变化及其对镉吸收的影响；乙烯和一氧化氮释放量的变化及相关基因表达量的变化，以期揭示NHX1提高浮萍镉耐受性的机制，并将利于镉污染水境的生态学修复。

工业污染的不当排放导致了水体重金属污染，镉污染对植物光合作用、元素吸收和生长发育造成严重危害。浮萍被广泛应用于水环境检测、生物产能和单子叶模式植物研究领域，本项目组发现大豆Na+/H+逆向转运蛋白（NHX1）在浮萍中过表达后，增强了浮萍的镉胁迫抗性，具体机制有待探索。.我们通过采用基因芯片、非损伤微测、电感耦合等离子光谱发生仪、流式细胞仪和荧光免疫技术等方法，对于NHX1在镉离子富集中的作用，以及在pH、信号通路和分子调控等进行解析，获得以下研究结果：（1）明确了NHX1提高浮萍镉胁迫抗性的生理机制：发现NHX1转基因浮萍通过增加镉外泌、减少根部镉的积累；揭示在短时间胁迫下NHX1转基因浮萍减少了镉离子内流，长期镉胁迫下NHX1转基因浮萍增加镉离子外排，进而减少了镉在转基因浮萍内的积累；抑制NHX1活性后，转基因浮萍镉离子内流增加；发现NHX1转基因浮萍活性氧积累降低，保护酶活性上升。（2）阐明NHX1转基因浮萍镉胁迫下的信号通路应答机制：研究发现24小时镉胁迫处理引发野生型浮萍NO含量的下降；而NHX1转基因浮萍内源NO含量显著性高于野生型浮萍；揭示了NHX1在短期镉处理中调节镉离子流和氢离子流的新功能。（3）研究NHX1转基因浮萍增强镉胁迫的分子机制：通过镉胁迫下NHX1转基因浮萍与根发育相关的基因显著性下调；NHX1转基因浮萍钙信号通路相关基因显著性下调，谷胱甘肽合成相关基因显著性上调；镉转运相关蛋白下调，液泡区域化相关蛋白上调。.研究成果为解析重金属镉逆境下植物的抗性机制提供重要理论依据，为污染水体的生态修复和经济作物减少镉积累提供理论支撑。