The Induction Of Systemic Genotoxicity In Arabidopsis Thaliana By Local Root Exposure To Metal(Oxide) Nanoparticles

The widespread availability of metal(oxide) nano-materials in the global market may lead to the release of a substantial amount of nano-particles (NPs) into the natural environment. The rapidly developing field of nanotechnology is likely to become yet another source through inhalation, ingestion, skin uptake, and injection of engineered nanomaterials. Thus the higher plants, as pivotal components of ecology, are inevitably subjected to various NPs. Plants represent the largest interface between the environment and biosphere, so understanding of the effects of nano-particles on plants is especially relevant for risk assessments of NPs. As yet, our knowledge about the effects of NPs on the plants, especially on the aspect of genotoxicity, is limited compared to these on plant growth and developments.In the current study, the model plants Arabidopsis thaliana(A. thaliana) were exposed to culture medium with various metal(oxide) nano-materials since seed germination, and some genetic and epigenetic changes such as DNA homologous recombination (HR) and alleviation of TGS was used to evaluate their genotoxicity. The main results were as follows:1. There are visual differences in different nano-materials using the transmission electron microscopy (TEM);2. The HRF is the number of recombination events per plant, which depends on not only the level of DSBs. A. thaliana plants of line R3L66 were germinated and grown on the medium containing ZnO-NPs, Ag-NPs and TiO2-NPs, and there are some changes of HRF in the aerial plants after exposure to metal(oxide) nano-materials. NPs can rise the transcription levels of HR-related genes in the seedlings, include AtRAD54, AtRAD51, AtXRCC3 and AtDMCl. Treated with NPs can reactive the TGS-silenced locus.Treated with NPs makes TGS-GUS locus displays some differences in methylation background at CG, CHG and CHH sites.3. Further, the mechanism of genomic instability in A. thaliana induced by NPs was investigated. ICP-MS result shows that the content of Zn, Ag and Ti elements in aerial plants is different, only the content of Zn is rise.Salicylic acid (SA) is a necessary endogenous signal molecule of systemic response in plants. The mutations of the sid2-2 and nprl-2 genes inhibited the induction of expression of the At RAD54 gene and TSI gene in aerial plants after root exposure to NPs.Treatment with 0.2% DMSO, a scavenger of ROS, could inhibit the up-regulation of At RAD54 gene and TGS gene induced by NPs.The level of ROS in the aerial plant after NP treatment is different.