纳米银是应用最广泛的纳米材料之一，其生物效应与安全性引起了各国的重视。研究表明纳米银可诱导植物根变短、主根负向重力性反应（主根失去向重力生长的特征，呈一定角度向上弯曲生长），但其作用机理尚不明确。本项目拟选择模式植物拟南芥为材料，通过比较不同类型纳米银、银离子的生物效应，银离子结合剂对纳米银与银离子生物效应的影响，结合纳米银在植株中的含量、形态与定位，阐明纳米银发挥生物学效应的形态；通过观察分生区细胞大小、数目与微管微丝的变化及淀粉粒的分布解析纳米银引起根变短、主根负向重力性反应的细胞学基础；通过分析生长素含量变化，生长素运输载体的作用，明确纳米银诱导拟南芥主根负向重力性反应与生长素的含量和极性运输的关系；通过GUS定量、Western-blot、突变体和转基因株系的表型分析研究纳米银诱导拟南芥主根负向重力性反应与AUX/IAA蛋白的关系。

Silver nanoparticles are one of the most widespread nanomaterials, and its biological effects has aroused great attention. Previous work demonstrated that silver nanoparticles (AgNPs) inhibits root elongation and induced primary root gravitropism loss. The mechanism of this phenomena is not clear. In this project, model plant Arabidopsis thaliana was used to elucidate the underling mechanism by the following aspects. 1 In order to elucidate which silver form that take biological effects, we will compare the biological effect of AgNPs, AgNO3 and bulk silver; compare the effect of cysteine (which binds Ag+) to nanosilver, AgNO3 toxicity; as well as measure AgNPs content, form and location in the plants; 2 Microscopic analyses of meristem zone length and meristematic cell number will be done to test the cellular basis of AgNPs-induced root gravitropism loss. Additionally, the level of auxin will be assayed by gas chromatography-mass spectrometry (GC-MS) to survey whether the changes of auxin content contribute to AgNPs-inhibited auxin signal. The possible role of auxin carriers PIN1, AUX1, PIN2/3/7 will be also investigated. Finally, a combinatorial approach of biochemistry, genetics, cell biology and molecular biology will be used to explore whether AgNPs-induced auxin signaling regulates though stabilizing the AUX/IAA protein for root development. The whole research project is expected to know the effect and mechanism of AgNPs to plants and to provide a scientific data for nanosilver safety evaluation.